The goal of this presentation is to discuss how to make decisions on whether or not a patient needs to go to surgery on an emergency basis and how to ensure the patient is as stable as possible preoperatively. Management of the patient in the immediate postoperative period in order to minimize patient morbidity and mortality will be discussed briefly.

Indications for Emergency Surgery

Not infrequently, dogs and cats will present with a history of trauma, an acute onset of clinical signs related to the abdomen, or more rarely, signs related to intrathoracic disease necessitating emergency surgery. Critically ill or injured patients often exhibit signs of some degree of cardiovascular shock. Patients should be stabilized if possible, but in some cases they cannot be stabilized until the surgery is performed. Some of these patients can, and should be managed medically, and some require emergency surgery (within minutes to hours of presentation); therefore, it is important to be able to determine rapidly whether or not surgery is indicated. If there is any doubt it may be better to perform surgery rather than wait and have the patient deteriorate.

All patients with penetrating wounds or open fractures should be taken to surgery within the first 6 hours of the injury for wound exploration. This is especially important with bite wounds where the damage under the skin is usually significantly worse than what the puncture mark would indicate. The presence of foreign material and necrotic tissue can lead to a systemic inflammatory response and ultimately death. If the patient is actively hemorrhaging surgery may be needed as part of resuscitation. Degloving wounds may be able to be managed with wet-to-dry dressings until they have been adequately resuscitated.

Patients presenting with acute abdominal conditions requiring emergency surgery are not uncommon. History may include signs of lethargy or depression, anorexia, retching, vomiting, diarrhea and abdominal distention. These patients are usually painful on abdominal palpation, although pain may not be clinically evident if the patient is severely depressed.

Acute abdominal conditions requiring emergency surgery include condition such as trauma-related disease (persistent hemorrhage, penetrating wound to hollow viscus, ruptured urinary bladder), gastrointestinal obstruction (foreign body, neoplasia), gastrointestinal accident (gastric or intestinal torsion or volvulus, intussusception), peritonitis, hepatic torsion, splenic torsion, abdominal masses, and vascular accident.

It is rare that patients will present with conditions requiring emergency thoracic surgery; however there are certain conditions where surgery will be indicated on an emergency basis. A severed trachea can occur secondary to penetrating trauma and hanging-type injuries. Severe tracheal tears in cats secondary to overinflated endotracheal tube cuffs should be surgically repaired as soon as possible if a significant pneumomediastinum or severe subcutaneous emphysema is developing. Patients with a tension pneumothorax may require emergency surgery if chest tube suction is not effective at decompressing the pleural space. Patients with a hemothorax should be taken to surgery if the amount of blood being suctioned via a chest tube is not decreasing.

Primary and Secondary Survey

On presentation a primary survey examination (evaluation of level of consciousness, airway, breathing, and circulation) should be completed within 30 to 60 seconds. Abnormalities should be treated as indicated. For instance the patient that presents obtunded with shallow respiration should be intubated and positive pressure ventilation should be instituted. (Not only will this help respiration but will also protect the airway against aspiration.) Depending on the severity of the patient's condition resuscitation may need to be instituted prior to performing a complete physical exam. A very brief history is obtained at this time if possible; however, resuscitation should not be delayed in the critical patient while a complete history is obtained. Instead permission should be rapidly obtained from the owner to allow treatment to be started.

A secondary survey, or complete physical examination, is completed once the primary survey is completed and resuscitation is instituted as indicated. Vital signs including blood pressure are taken at this time. Rectal thermometers may induce a vagally-mediated arrest in the severely bradycardic or hypotensive patient and should be avoided in these patients. Toe web temperatures can be taken and compared with rectal temperatures. If the patient is perfusing normally the Delta T should be less than 7 degrees Fahrenheit. The jugular vein should be clipped and evaluated for distention, filling (<3-4 secs) and relaxation (<1-2 secs) times since this will provide a crude estimate of central venous pressure (CVP) as well as right heart function. Patients with surgical conditions of the abdomen may have concurrent pneumothorax, secondary aspiration pneumonia, metastatic disease, etc., and close attention should be paid to the ventilatory pattern, presence of cough, and bilateral auscultation of the thorax. The abdomen should be palpated, ausculted and percussed with the goal of localizing pain, and detecting the presence of fluid waves, gas-filled organs or solid masses. A rectal exam should be performed and the presence of blood noted. The ventral abdomen should be clipped. Petechiation or ecchymoses may indicate thrombocytopenia, a coagulopathy or disseminated intravascular coagulation (DIC). Periumbilical hemorrhage may be seen with a hemoabdomen and periumbilical masses may be seen with pancreatic carcinoma. Distended superficial abdominal veins are consistent with increased intra-abdominal pressure, which can be associated with decreased preload and decreased cardiac output.

Resuscitation

The goal of resuscitation is to reverse the signs of shock and provide effective oxygen (O2) delivery to the cells. The delivery of O2 is based on the cardiac output (stroke volume x heart rate) and the arterial content (CaO2) of O2 (CaO2 = [Hb x SaO2 x 1.34] + [PaO2 x 0.003]). The patient must be able to effectively exchange O2 and CO2 at the alveolus. There must be sufficient hemoglobin (Hb) to carry the O2, sufficient blood volume (preload), and an effective pump (heart). Resuscitative efforts should be directed at maximizing these parameters.

Oxygenation and Ventilation

Patients presenting with signs of shock should have O2 administered. The easiest way to provide supplemental O2 on an immediate basis is via flow-by. Tubing is held up to the patient's face and O2 is delivered at high rates (5-15 l/min). Oxygen also can be given by mask, baggie or oxygen hood. If the patient is panting these methods may lead to excessive heat build-up and the temperature of the patient should be monitored. In obtunded or cold patients the use of these methods of delivery may help warm the patient. If the patient is showing signs of severe respiratory distress or is obtunded, intubation and positive pressure ventilation may be necessary. Prolonged O2 supplementation is often required in which case a nasal O2 tube should be placed. If pulse oximetry is being monitored O2 saturation (SaO2) should be maintained above 94 percent. Patients with SaO2 less than 92% on supplemental O2 should be intubated and positive pressure ventilation should be instituted. Caution should be used in interpreting pulse oximetry in awake patients since tissue perfusion, movement, and skin pigmentation can cause erroneous readings. An arterial blood gas should be assessed if there are any concerns.

If there is sufficient distention of the abdomen to interfere with ventilation, measures should be taken to remedy this. In the gastric dilation and volvulus patient, the stomach should be decompressed once fluid resuscitation has been addressed. Severe abdominal distention from fluid accumulations may need to be addressed by drainage of the fluid. Dorsal recumbency should be avoided in these patients since the additional pressure on the abdominal vena cava can significantly decrease preload.

Blood Pressure

Elevated heart rates in patients in shock usually imply hypovolemia or pain. Hypovolemia triggers the baroreceptors and the heart rate elevates in an attempt to restore normal blood pressure. Blood pressure can be estimated by palpating pulses, but extreme caution is warranted. The strength of central pulses (femoral pulse) is based on the pulse pressure (the difference between the systolic pressure and the diastolic pressure). Thus, a blood pressure of 120/80 is equal to a pulse pressure of 40, as is a blood pressure of 100/60. However, these 2 values would dictate different therapeutic approaches. Skill plays a large role in the ability to palpate pulses. The femoral pulse becomes nonpalpable between 30 and 60 mm Hg systolic pressure depending on the skill of the clinician, and patient parameters such as obesity, shivering or shaking. Blood pressure should be measured for more objective assessment that that afforded by palpation of pulses alone.

Mean arterial pressure is calculated as two-thirds of diastolic pressure and one-third systolic pressure (corresponding to the time the heart spends in systole and diastole respectively). Mean arterial pressure is important because mean pressures affect organ perfusion. For instance, at less than 60 mm Hg mean arterial pressure renal perfusion is compromised. Blood pressure can be measured directly using an arterial catheter or indirectly using an oscillometric or a Doppler device. Direct blood pressure measurements are most accurate but not available in many hospitals. Oscillometric devices measure blood pressure by detecting flow pulsations beneath a cuff. Systolic, diastolic, and mean arterial pressure are displayed on a digital readout. Oscillometric devices are affected by shivering or shaking, small patient size, and low flow states (vasoconstriction, low blood volume, hypothermia). Doppler devices require the placement of an ultrasonic flow probe over an artery (usually the palmar arterial arch of the metacarpal or metatarsal region). The sound generated is a reflection of blood flow. A pressure cuff is placed proximal to the flow probe and inflated. Measurements are taken using a sphygmomanometer. The first sound that is heard is the systolic blood pressure and the second sound (or a sudden change in pitch) is diastolic blood pressure. With practice diastolic blood pressure can be fairly accurately assessed using a Doppler unit.

Doppler devices have the advantage of allowing the clinical to assess blood pressure as well as flow to the area (an indicator of perfusion). They can also be used to monitor the patient for arrhythmias since premature ventricular contractions, atrial fibrillation and sinus arrest can be detected by changes in the sound of the Doppler flow. Doppler ultrasonic pressure readings are affected by low flow states (vasoconstriction, low blood volume, hypothermia).

Central Venous Pressure

Preload is assessed most effectively by measuring central venous pressure. A jugular catheter is placed with the tip being as close to the right atrium as possible. An extension set or fluid manometer is attached to the jugular catheter. The fluid column is allowed to flow freely into the jugular catheter. When the pressure in the jugular vein equals the force of gravity the fluid column will remain static (except for oscillations associated with intrathoracic pressure changes during inspiration and expiration). A measurement is taken from the level of the right atrium to the top of the fluid column. (The thoracic inlet can be used as a zero point.) Pelvic limb catheters can be used as long as the tip of the catheter is in the abdominal vena cava; however, abdominal CVP measurements will not reflect thoracic central venous pressure if there is increased intraabdominal pressure. In the patient with no central catheter the jugular veins should be clipped and examined for distention, filling and relaxation times. Patients with hypovolemic shock will have flat jugular veins and poor filling when they are held off at the thoracic inlet. Increased central venous pressure in shock is an indicator of elevated intrathoracic pressure from a pneumothorax, a mass pressing on the cranial vena cava, pericardial tamponade, right-sided heart failure, or fluid overload. Since each of these will affect cardiac output they must be identified and treated.

Vascular Access

All patients in shock should have fluids should be administered into a vascular space. Typically this involves placement of a peripheral catheter; however central catheters may be indicated in some patients, and intraosseous access may be the only accessible route in very small patients, reptiles, birds and rodents. Peripheral vascular access can be achieved by placing a catheter in the cephalic or lateral saphenous vein in the dog and the cephalic and medial saphenous veins in the cat. Rapid fluid administration is indicated in most patients in shock and since flow is directly proportional to the radius to the fourth power and indirectly proportional to length, a large gauge, short catheter will allow the most rapid administration rates. General guidelines are as follows: 18 ga in cats and smaller dogs, 16 ga in medium-sized dogs (10-30 kg), and 14 ga in larger dogs (greater than 30 kg). One large bore short catheter may be sufficient for patients in mild shock; however, those patients in severe shock should have two large bore catheters placed.

Since these patients may be hypovolemic the veins may not stand up well. Lowering the vein below the level of the heart may help improve filling. Penetrating the skin can be the most painful part of the procedure. In addition burring usually occurs during penetration of the skin. A small cutdown using the bevel of a hypodermic needle decreases pain and the likelihood of burring and permits a larger catheter to be placed than might otherwise be possible. A larger cutdown can be made using the same hypodermic needle. A cut is made over the vein across the tension line of the skin - generally in a craniomedial to caudolateral direction at 15-30 degrees off the horizontal. The vessel can be dissected further if necessary using the needle as a "mini scalpel" with the bevel directed parallel to the vein. Placing triple antibiotic ointment or povidone-iodine ointment over the venotomy site followed by placement of a sterile bandaid or sterile 4 x 4 gauze square helps control infection.

Central catheters should be placed whenever central venous pressure monitoring is indicated, when hypertonic fluids are to be infused or whenever frequent blood sampling is required. Asepsis is essential. Either a peel-away, Seldinger or feeding tube technique can be used. The first two require a commercial catheter, (Arrow, Cook Veterinary Products). The last requires a feeding tube and a large bore over-the-needle catheter. Central lines are generally placed in the jugular vein; however the lateral saphenous (dog) or medial saphenous (cat) also can be used. Ideally the catheter tip should be near the entry to the right atrium.

Fluids

The choice of fluids therapy is dictated by the cause of the shock. Ideally the fluids uses to treat patients should be identical to the fluids lost by the patient. If the patient lost 40% of its blood volume out on the pavement then whole blood is going to be an essential part of the fluid resuscitation. If the patient has been vomiting for 2 days and has lost electrolytes then electrolyte-replacing fluids are essential. If the patient has a protein-losing enteropathy or a severe vasculitis then fluids, that provide colloid support to counteract the effects of the lost proteins will be needed. Fluids should be given as fast as necessary to resuscitate the patient.

Crystalloids

Crystalloids are fluids containing sodium chloride and other solutes that are capable of distributing to all body fluid compartments. The most commonly used replacement fluids are 0.9% saline, lactated Ringer's solution and Normosol-R or Plasmalyte-A. Buffered solutions are usually indicated for resuscitating patients in shock since administration of a highly acidotic solution may worsen a preexisting metabolic acidosis. The exception to this is the patient with a metabolic alkalosis from a gastric outflow obstruction or a patient with a concurrent Addisonian crisis. Electrolyte abnormalities should be corrected based on lab results.

Hypertonic saline is a hyperosmolar crystalloid fluid used for resuscitation of hypovolemia. It is usually given as a 7.5% solution (2600 mOsm/L). The hyperosmolarity leads to rapid intravascular volume expansion by drawing fluids from the interstitial and intracellular space into the intravascular space. Its major benefit is that it can produce an equivalent intravascular volume expansion to colloids but at one-fourth the volume. Because it is a crystalloid it will rapidly redistribute similar to all other sodium chloride-based solutions; however, its effects can be prolonged by concurrent administration of a colloid.

Since approximately 80% of extracellular fluid is in the interstitial space crystalloids will rapidly redistribute and after approximately 1 hour there will be only 20% of the administered volume remaining in the circulation. On a short-term basis crystalloids will expand the intravascular space, but this effect will be short-lived. Thus, crystalloids should be thought of as interstitial dehydrators, not intravascular volume expanders. This increase in interstitial fluid can lead to tissue edema (thus decreasing the ability of oxygen to diffuse to the cells). Interstitial edema may be extremely detrimental in cases of cerebral edema and pulmonary edema.

Colloids

Colloids are fluids containing large molecular weight substances that generally are not able to pass through capillary membranes. Colloids can be considered intravascular volume expanders. Since most patients in shock require sustained intravascular volume expansion, colloids are indicated frequently during fluid resuscitation. Examples include synthetic colloids such as the dextrans, hetastarch, Oxyglobin??, and biologic colloids such as whole blood, plasma, and albumin. All synthetic colloids have the potential to cause a dilutional coagulopathy.

Ideally blood should be used for resuscitation if the patient has lost whole blood. The lower the hematocrit becomes the more important this is to ensure adequate oxygen delivery to the cells. If the patient has lost clotting factors then clotting factors should be replaced. This means administering fresh whole blood or fresh frozen plasma. Platelets are only found in fresh whole blood (administered within 6-8 hours) and in platelet-rich plasma. If the patient has a low albumin or a loss of clotting factors then fresh frozen plasma should be used. If only albumin is low frozen plasma or albumin can be given.

Dextran 70 has an average molecular weight of 70,000 which is the same size as the albumin molecule. Dextran 70 can cause red blood cell cross-linking that leads to rouleaux formation, which may interfere with cross matching.

Hydroxyethyl starch is a molecule made from maize or sorghum and is primarily an amylopectin. Hetastarch has an average molecular weight of 450,000 Daltons and has a half-life of 25 hours. Because of its size and half-life hetastarch provides an effective means of expanding the intravascular volume for an extended time. Doses greater than 20 ml/kg/day have been associated with an increased incidence of bleeding problems, which may be due to dilution, increased microvascular perfusion, or decreased platelet aggregation. Increases in activated clotting times associated with hetastarch (up to 180 seconds in dogs and 120 seconds in cats) have been noted. In cats the dose should be infused slowly as hypotension (related to histamine release??) may result with boluses. Pentastarch has a much shorter half-life than hetastarch (2.5 hours), but otherwise has similar effects and side effects.

Hemoglobin-Based Oxygen Carriers

Hemoglobin-based oxygen carriers are indicated during resuscitation when increased oxygen delivery to tissues is desired. Oxyglobin® is a purified, polymerized bovine hemoglobin that is in a modified lactated Ringer's solution that is approved for use in dogs. It is isoosmotic and has an average molecular weight of 200,000 making it a very effective colloid. It has a pH of 7.8. Its oxygen affinity is dependent upon the chloride ion concentration not the concentration of 2,3-diphosphoglycerate (2,3-DPG). This provides a distinct advantage over blood that has been stored longer than 1 week that may have significantly depleted 2,3-DPG levels leading to increased oxygen binding and decreased oxygen delivery at the tissue level. In addition the normal oxygen affinity of Oxyglobin® is lower than that of normal canine blood which enhances delivery of oxygen to the tissues. It has a lower viscosity than canine blood that may improve microvascular flow. Because it is a smaller molecule than red cells it is able to perfuse tissue beds that red cells may not be able to reach.

Oxyglobin can be administered via standard intravenous administration sets and standard intravenous infusion pumps can be used for delivery. Because it contains no antigens cross matching is not required and there is no possibility of transfusion reactions. Once opened the bag must be discarded within 24 hours due to the production of methemoglobin.

Oxyglobin® is up to 10 times more effective than blood when given during fluid resuscitation to animals in hemorrhagic shock. For this reason, low volumes of Oxyglobin® can be used effectively to treat hemorrhagic shock. (See below) It has a short half-life (30 to 40 hours); however, the length of clinical benefit is currently unknown. Primary effects last about 24 hours and 90% of the Oxyglobin® is eliminated in 5-7 days.

Side effects include discolouration of mucous membranes, sclera and urine, which affects patient monitoring. Measurements of all colourimetric lab tests are affected for 24 to 72 hours after administration of Oxyglobin®. Packed cell volumes do not correlate with hemoglobin, therefore, hemoglobin levels need to be measured directly.

Oxyglobin® must be used with caution is patients that are euvolemic (i.e., immune-mediate hemolytic anemia), and should be used with extreme caution in patients that are hypervolemic (i.e., patients with congestive heart failure or oliguric/anuric renal failure) because it is a colloid. This means it will expand the intravascular space by at least its own volume. These conditions are not necessarily contraindications but the clinician must deliver the fluid over a longer period of time and the patient must be monitored closely for signs of volume overload. These signs include increased jugular vein distention, increased ventral venous pressure, increased respiratory rate or effort, and crackles on auscultation. It should be kept in mind that by the time signs of pulmonary edema occur the clinician missed the earlier signs of fluid overload. Since cats appear to be more predisposed to rapid onset of pulmonary edema when fluid overload occurs, the author recommends infusion of Oxyglobin® over a minimum of 8 hours in euvolemic cats. In hypovolemic cats Oxyglobin® is infused as any other colloid would - over 10 to 20 minutes.

How Much Fluid?

The amount of fluid to be administered during resuscitation must be based on restoring normal oxygen delivery. This means fluid is administered until respiratory rate and effort are normalized, heart rate is normalized, blood pressure and central venous pressure are normalized, mucous membrane colour and capillary refill time are normalized, temperature (toe web and central) is normalized, and urine output is normalized.

While the blood volume of the dog is approximately 80 mL/kg the blood volume of the cat is approximately 60 mL/kg. These numbers are kept in mind during fluid administration. In the author's experience fluid resuscitation is started with a bolus of 20-30 ml/kg of a buffered, balanced electrolyte solution. (This volume is reduced by approximately 30% in cats.) If the patient is suspected, based on clinical presentation or initial lab work, of having a low colloid osmotic pressure then synthetic colloids are used during initial resuscitation with boluses of 5 ml/kg to a maximum of 20 ml/kg. (In cats a bolus of hetastarch is never given faster than over 15 to 20 minutes.) After each bolus the patient's physical parameters are reassessed. Once parameters have been normalized fluid resuscitation is slowed to maintenance rates. If the patient is assessed to be in hypovolemic shock from blood loss, or is thought to have a protein-losing vasculitis, or is a potential candidate for disseminated intravascular coagulation, then an attempt is made to use blood products during resuscitation. This prevents dilution of remaining hemoglobin and clotting factors. Blood can be infused as fast as necessary to restore perfusion parameters.

Recent studies have shown that low volume resuscitation with a HBOC may restore aerobic metabolism although hypovolemia, hypotension and low cardiac output persist. Low volumes of a HBOC also will not restore hemoglobin levels to 7 to 10 g/dL. Since the goal of resuscitation is to restore oxygen delivery to tissues this may require a paradigm shift in resuscitation protocols as well as the development of new methods of measuring tissue perfusion. Doses of Oxyglobin® as low as 3 to 5 ml/kg may be effective in improving tissue oxygen delivery in moderate shock and doses as low as 7 to 8 mL/kg may be all that is indicated in severe hemorrhagic shock. The author recommends infusion of 3 to 8 mL/kg of Oxyglobin® in patients showing signs of hemorrhagic shock in addition to volumes of crystalloids as noted above and plasma as needed to avoid a coagulopathy from developing.

Coagulation

The triad of hypothermia, acidosis, and coagulopathy has been called the "trauma triad of death" Many patients in shock may have coagulopathy. This should be kept in mind when fluids are chosen for resuscitation. It is important not to worsen any preexisting coagulopathy by excessive dilution of clotting factors using crystalloids or synthetic colloids, by improving the acid-base status and by avoiding hypothermia. This means that the appropriate fluids should be administered based on the underlying disease and that fluids should be warmed to body temperature - especially if the fluids are being given very rapidly. Crystalloids play a role in resuscitation; however, caution should be exercised to ensure the triad of death is being avoided through judicious use of warm fluids, HBOC, and blood products.

Analgesia

Analgesia is a key part of treatment for most emergency patients when surgery is a consideration. Non-steroidal anti-inflammatory drugs should be avoided due to their negative effects on splanchnic organs. Opioids such as butorphanol, oxymorphone, morphine and fentanyl are recommended. They should be given intravenously since absorption from subcutaneous or intramuscular sites may be unpredictable. In cases of severe pain constant rate infusions may be required. Alternatively epidural analgesia using morphine or oxymorphone can be administered. This is a very effective means of controlling pain and minimizes the amount of general anesthesia required intraoperatively. If an epidural catheter is placed repeat doses can be given. In the critical patients doses of opioids may need to be reduced to 25-50% of normal since the patients often cannot tolerate usual doses.

Diagnostic Tests

Diagnostic tests are required frequently in order to determine the extent of the disease and to confirm the diagnosis. Resuscitation of the critical patient should not be delayed while tests are being performed unless those tests are required to guide resuscitation. Lab tests including packed cell volume, total solids, azostick and glucose should be part of a stat database. Many septic patients are hypoglycemic and require dextrose supplementation in the fluids. Ideally a complete blood count with microscopic evaluation of a blood smear for the differential, electrolytes, blood gas (venous or arterial), coagulation panel (prothrombin time and activated partial thromboplastin time or activated clotting time), blood chemistries, fecal, Parvovirus test, and urinalysis should be performed. The choice of tests may vary to some degree based on the presenting complaint. Survey chest and abdominal radiographs are indicated especially preoperatively in every trauma patient. Contrast studies including barium series, intravenous urography, cystography (single and double contrast), and angiography may be required. Barium should not be used if there is concern for gastrointestinal perforation or aspiration. Water-soluble contrast material should be used instead. Abdominal ultrasound can be very useful for diagnosing many causes of acute abdomen unless there is a significant amount of air within the peritoneal cavity. Abdominal centesis or paracentesis should be performed in 4 quadrants (unless ultrasound-guided centesis is available). Abdominocentesis may be falsely negative, and diagnostic peritoneal lavage (DPL) should be performed if a confirmation of the diagnosis is required. A packed cell volume, protein level, white blood cell count and microscopic examination of the fluid should be performed. Results of DPL fluid examination are extremely useful for determining the need to exploratory surgery in cases where the diagnosis is uncertain.

An electrocardiogram should be assessed for the presence of arrhythmias and signs consistent with myocardial hypoxia/ischemia. Ventricular premature contractions (VPC) and ventricular tachycardia are the most common malignant arrhythmias seen. Ventricular premature contractions should be treated if they are multifocal, are affecting perfusion (significant pulse deficits), the heart rate is elevated (usually above 160 beats per minute), or there is evidence of R on T phenomenon. Treatment includes the use of supplemental oxygen, ensuring tissue perfusion is being maximized, and a constant rate infusion of antiarrhythmics (lidocaine and/or procainamide).

Hypothermia

Patients with an acute abdomen may present with hypothermia. Or they may become hypothermic during resuscitation secondary to intravascular infusion of large volumes of room temperature fluids. Hypothermia interferes with normal metabolic functions leading to vasodilation, cardiac dysfunction, and interference with the coagulation cascade. Core rewarming should be instituted since peripheral rewarming may lead to worsening of the vasodilation and subsequent worsening of the hypothermia. Artificial warming devices should be insulated from the patient since they can cause burns. Means of rewarming patients includes the use of warm water bottles, warm water circulating blankets, oat bags, warm blankets, and hot air circulating devices. Fluids should be infused at normal body temperature in the hypothermic patient.

Other Treatments

If the patient is vomiting or regurgitating a nasogastric tube should be placed for gastric decompression. This can be used postoperatively for both decompression and early enteral feeding.

Most patients should be started on broad-spectrum antibiotics to cover both aerobic and anaerobic bacterial infections pending results of any cultures. Patients requiring emergency surgery often have conditions causing immunocompromise (trauma, neoplasia, etc) or they have underlying infections. Perioperative antibiotics are always indicated although they may not need to be continued for any length of time in the postoperative period depending on intraoperative findings.

Monitoring

The patient should be closely monitored while it is being resuscitated and prepared for surgery. Vital signs, BP, CVP, electrocardiogram, and pulse oximetry should be evaluated as frequently as continuously to as infrequently as every 30 to 60 minutes if the patient is stable. All numbers should be recorded since often the trend of change is more important than the absolute numbers. While the patient is under anesthesia similar monitoring should take place but the patient should be evaluated every 5 minutes.

Postoperative Care

Postoperatively the patient should be monitored in a similar fashion as it was preoperatively. The patient should be aggressively rewarmed. Care should be taken when using rectal thermometers as many postoperative patients are hypothermic and bradycardic and placement of a rectal thermometer may trigger a vagal arrest. Vital signs should be returned to normal as soon as possible. The endotracheal tube should remain in place with the cuff inflated until the patient is awake and has a strong swallow reflex. Regurgitation and aspiration can occur at any time and may not infrequently occur during recovery. For this reason the cuff should remain inflated until the patient is ready to be extubated. A nurse or doctor should remain with the patient until extubation. All patients with decreased gastric motility (most postoperative exploratory laparotomy patients and most patients experiencing shock) should have a nasogastric tube placed and aspirated to ensure gastric decompression. This helps decrease the chance for bloat, interference with diaphragmatic excursions, and has been proven to significantly decrease the time it take for normal gastric motility to return. Lab tests should be run in the immediate postoperative period to ensure that parameters such as packed cell volume, albumin, electrolytes, urea nitrogen and glucose are in the normal range.

Goals for Success

The primary goals of the ABC's apply equally under anesthesia as to the awake patient. Almost all anesthetic agents are respiratory depressants and cardiovascular depressants. Therefore, the goal should be to ensure that the patient's respiratory and cardiovascular parameters remain as close to normal as possible. Whereas the normal healthy patient often has enough reserves to draw upon to tolerate adverse effects of general anesthesia, the critically ill or injured patient may not. The patient must have a patent airway, must be oxygenating and ventilating well, and must be delivering the oxygen to the tissues and picking up the carbon dioxide from the tissues. Preload (venous volume), blood pressure (BP), heart rhythm, must remain normal. In addition acidosis (related to poor perfusion and hypoventilation) can cause abnormalities in enzymes systems, cardiac function and coagulation and should be corrected prior to anesthesia whenever possible. Hypothermia can have similar adverse effects. Hemoglobin should be maintained in an adequate range (approximately 10 g/dl minimum) to ensure adequate oxygen delivery to the tissues. If hemoglobin-based oxygen carriers (OxyglobinÒ, Biopure Corporation) are being used it is possible lower hemoglobin levels may be well tolerated by the patient. High hemoglobin levels should be avoided to decrease the likelihood of "sludging. Electrolytes should be maintained in as normal a range as possible to ensure good muscle function.

It is essential that a full preanesthetic exam including a complete physical exam, laboratory analysis and radiographic analysis be performed. Close attention should be paid to tracheal and thoracic auscultation, observation of respiratory effort, cardiac auscultation, evaluation of jugular vein distention and filling, and pulse palpation (central and peripheral). Vital signs (TPR) including a presedation BP should be recorded. An accurate weight should be recorded. Lab work should include a minimum of a packed cell volume and total solids (PCV/TS), glucose, blood urea nitrogen, electrolytes and albumin. Coagulation parameters such as a prothrombin time (PT), activated partial thromboplastin time (aPTT) or activated clotting time (ACT), and a platelet estimate are highly recommended. Ideally a full complete blood count and chemistry panel and urinalysis should be performed but under emergency conditions that is not always possible. A venous blood gas helps determine the metabolic status of the patient (relates to tissue perfusion) as well as ventilatory capability and ideally should be performed on all critical patients. Chest radiographs are indicated in all critical patients and in all trauma patients.

One or two large bore peripheral catheters should be placed in case rapid volume infusion is required. A central line should be placed in all patients in which central venous pressure (CVP) monitoring is indicated to estimate venous volume or preload. Central lines also are useful in patients requiring infusions of hyperosmolar fluids or frequent blood sampling.

Patients should be stabilized as much as possible prior to induction of anesthesia. Supplemental oxygen should be provided, intravenous fluids should be administered, and chest tubes should be placed in all patients with a pneumothorax. It should be kept in mind that crystalloids are interstitial rehydrators, not intravascular volume expanders. In addition crystalloids and synthetic colloids will dilute clotting factors if given in excessive quantities. This should be avoided through smaller volume resuscitation and judicious use of plasma or fresh whole blood. Transfusions should be given to those patients with severe anemia or coagulopathies. OxyglobinÒ is useful primarily for its oxygen-carrying properties in the author's opinion, but as a colloid it also will help with volume expansion.

Drugs

Almost all analgesic and anesthetic drugs in critically ill or injured patients should be reduced by 25 to 50% and should always be titrated to effect since their metabolism, albumin levels, volume of distribution, and excretion capacity often is altered. It is easier to titrate upwards than to have to deal with side effects and complications associated with an "overdose". Drugs should be given intravenously whenever possible since absorption from subcutaneous routes is unpredictable.

Goals of Anesthesia

The primary goals of anesthesia are to eliminate pain and ensure amnesia. All patients should be managed with these 2 goals in mind.

Analgesia

NO patient is so sick that pain relief cannot be provided. Medication should be given preoperatively to prevent windup and continued intraoperatively and postoperatively.

Opioids

Opioids should be given on an "as needs" basis rather than on a schedule. For instance, if the patient seems to be responding to surgical stimuli additional analgesics may be indicated as opposed to just more inhalant anesthetic to mask the actual problem.

Parenteral opioids are the primary drugs indicated and should be given intravenously or epidurally. Transdermal fentanyl may be effective in the longer term but may take 8-12 hours or longer to take effect. In addition, warming and cooling of the skin seriously affects absorption. Opioids may cause bradycardia and anticholinergics are indicated if the low heart rate is adversely affecting blood pressure.

Morphine can be used effectively for short-term analgesia and is an excellent choice for constant rate infusions for controlling significant pain. It is very effective when given epidurally. Morphine can cause vasodilation and emesis. It is the least expensive of the opioids. Butorphanol is a short acting analgesic with minimal sedative and respiratory depressant effects. Because of these characteristics it is very useful in very critical patients or in patients who have not been full cardiovascularly resuscitated. It can also be titrated effectively intraoperatively with minimal cardiorespiratory effects. However, it has a short duration of action (sometimes as little as 20 minutes) and clinically it is not as effective as other opioids so it has less usefulness for long term pain management. Oxymorphone is an intermediate acting opioid that clinically is effective at controlling most pain. It also is effective when given epidurally. Common side effects include panting (actually hypoventilation) and noise sensitivity. Hydromorphone is similar to oxymorphone although it seems to be clinically less effective with more side effects (emesis, dysphoria). Fentanyl is a very short acting opioid that must be delivered frequently or via constant rate infusions. It is a very effective analgesic to use both perioperatively and intraoperatively. It can cause significant bradycardia and heart rates should be monitored closely. Transdermal fentanyl may be effective in the longer term but may take 8-12 hours or longer to take effect.

Local Anesthesia

Local anesthesia can be very useful decreasing pain and decreasing amounts of general anesthesia and systemic analgesics. Lidocaine or bupivicaine or both mixed together in 50:50 volumes typically are used. The local anesthetic can be injected into wound edges, onto tissue beds, regionally, intraarticularly, intrapleurally, or intercostally. Pain related to the acidic nature can be modified by warming the drug to body temperature or by adding 10% of the volume as sodium bicarbonate. Dilution of lidocaine when it is used as a local anesthetic to 1% can be useful in minimizing total drug dose while provided adequate volume for the block.

Local anesthetic agents also can be used intravenously at low dose constant rate infusions to provide additional analgesia. (Lidocaine has been used at 1 mg/kg/hr in the awake patient.) Patients receiving intravenous doses or higher doses of local anesthetic agents should be monitored closely for hypotension.

Epidural Analgesia and Anesthesia

Epidural analgesia and anesthesia significantly decrease the dose of systemic medications required. Epidural catheters allow for provision of longer term analgesia can allow higher blocks to be provided. Usually lidocaine or bupivicaine are used in conjunction with morphine or oxymorphone or hydromorphone. The beneficial effects may last as long as 6 to 24 hours. With an epidural catheter in place additional opioids (and local anesthetic medications) can be provided intraoperatively and postoperatively. Although multiple side effects including bradycardia, hypotension, respiratory depression, motor paralysis, hypothermia, urinary retention and infection have been reported, all but bradycardia are rare in the author's experience. Some of these effects are minimized and motor paralysis is avoided if local anesthetics are not infused. Local anesthetics should not be used or should be used with extreme caution with high epidurals (epidural catheter in thoracic region).

Ketamine

Constant rate infusions of low dose ketamine (0.1 to 1.0 mg/kg/hr) given to effect also have been used in painful patients and may be a helpful adjunct.

Nonsteroidal Antiinflammatory Drugs

Nonsteroidal antiinflammatory agent generally should be avoided in critically ill or injured patients due to their negative gastrointestinal and renal effects. In addition some have negative effects on coagulation. Some of the newer generation COX-2 specific drugs may prove to be safe to use in more critical patients; however, they are not recommended in patients with hypovolemia, compromised gastrointestinal perfusion (related to circulatory disturbances or underlying disease processes), and renal disease.

Other Premedication Agents

Anticholinergics should only be administered in the face of significant bradycardia or bradycardia significant enough to cause hypotension since tachycardia can be very detrimental due to the increased workload on the heart. Phenothiazines should generally be avoided due to the vasodilatory effects of this class of drug that can lead to refractory hypotension.

Induction

Rapid induction to gain control of the airway always should be performed in critical patients. Mask or tank inductions should be avoided since struggling can increase metabolic oxygen requirements, patients may further injure themselves, and hypoxia and hypercarbia during the induction process may cause serious complications. A laryngoscope should be used to ensure accurate intubation and avoid laryngeal stimulation which can increase vagal input.

Neurolept Anesthesia

Neurolept anesthesia refers to a dissociative, analgesic state produced by the synergism between an opioid and a tranquilizer. It may provide anesthesia in the severely debilitated patient. In less debilitated patients, doses of inhalants can be significantly reduced. Awake intubation can often be performed with these combinations. Awake intubation is the placement of an orotracheal tube in the patient that is not unconscious, but rather is in a dissociative state. Examples of neuroleptanalgesia include butorphanol and a benzodiazepine (diazepam, midazolam), butorphanol and acepromazine, oxymorphone and a benzodiazepine, and oxymorphone with acepromazine.

Etomidate

Etomidate is an imidazole derivative that is classified as a nonbarbiturate, non-narcotic, sedative-hypnotic agent. It has poor analgesic qualities and opioids or other means of providing analgesia should be administered if etomidate is being used. It causes mild respiratory depression but minimal change in cardiopulmonary function even in hypovolemic dogs. Vomiting, excitement, tremors and apnea may be seen on induction. The neurologic signs are thought to be due to disinhibition of subcortical neural activity and are not seizures. Etomidate causes cortisol suppression for up to 6 hours and in dogs and cats after a single injection. The significance of this in a stressed patient is unknown.

Ketamine/benzodiazepine combinations

Ketamine in combination with a benzodiazepine such as diazepam or midazolam makes an excellent combination for induction of anesthesia in critical patients. Midazolam is a water-soluble benzodiazepine with similar effects to diazepam but a longer half-life. Subjectively there appear to be fewer dysphoric effects with midazolam than with diazepam and the effects last longer. Ketamine is a dissociative anesthetic that has good musculoskeletal analgesic properties, weak visceral analgesic qualities, and poor muscle relaxant properties. It exerts a positive inotropic effect on the myocardium. It should be avoided in cats with hypertrophic cardiomyopathy, in patients with increased intracranial pressure, and in patients at risk for seizures. Benzodiazepines are metabolized in the liver and should be used with caution in severe liver disease. Ketamine is metabolized in the liver in the dog; however, in the cat it is excreted primarily unchanged in the urine.

Medetomidine

Alpha 2 agonists such as xylazine and medetomidine are usually contraindicated in critical patients. They cause a decrease in heart rate of up to 50% of baseline. They can also cause atrioventricular block and ventricular premature contractions.

Propofol

Propofol is an alkyl phenol classified as nonbarbiturate, nonnarcotic, sedative-hypnotic that has poor analgesic qualities. Because of its short acting nature it is often used in ill or injured patients; however, it causes apnea and systemic hypotension. The hypotension is secondary to a decrease in myocardial contractility, as well as both vasodilatation and venodilation. For all of the above these reasons it makes a poor choice for use in critical patients.

Barbiturates

Both thiobarbiturates (thiopental) and oxybarbiturates (pentobarbital) can be used for providing general anesthesia. However, since they have significant respiratory depressant qualities as well as negative inotropic properties which can cause hypotension, they must be used with caution. The negative effects are intensified in the presence of shock, acidosis, hypothermia, and hypoproteinemia. Pentobarbital can be used very effectively at low doses throughout anesthesia as part of a balanced anesthesia regimen but because of their severe depressant effects barbiturates should not be used for induction without premedication. Barbiturates have no analgesic qualities and must be used in combination with opioids. Advantages include rapid induction which allows for rapid intubation and control of ventilation. They also decrease cerebral metabolic oxygen consumption and can be used safely in patients with intracranial disease. Lack of body fat and liver dysfunction significantly prolong recovery from thiobarbiturates and they should be used with caution in thin patients or patients with liver disease.

Inhalant Anesthesia

Isoflurane is the most commonly used inhalant anesthetic. It causes significant dose-dependent decreases in blood pressure and cardiac output, which could be life threatening in the critical patient. This is related to combination of negative inotropic effects and vasodilatory properties. Although inhalant anesthesia may be required it should be used with extreme caution in the critical patient and whenever possible balanced anesthetic technique with a neurolept anesthesia protocol should be used.

Ventilation Support

All anesthetic agents are ventilatory depressants, and as such, ventilatory support is essential in the critical patient. This is most simply done using a mechanical ventilator but in the absence of one "hand bagging" can be performed. In general tidal volumes of 7 to 10 ml/kg and a rate of 10 to 15 breaths/min should be used. Peak inspiratory pressures should be kept below 15 cm H2O whenever possible. Tidal volumes as high as 15 to 20 ml/kg and peak inspiratory pressures as high as 25 cm H2O may be required. Tidal volumes are adjusted based on observation of chest movement during ventilation, lung auscultation, blood gases, capnometry and blood pressure. To avoid complications the lowest volumes and pressures should be used, as the patient will tolerate. Overventilation can lead to a decrease in preload and a secondary decrease in cardiac output and blood pressure.

Hypothermia

Hypothermia is a very common problem in anesthetized patients and aggressive attempts should be made to maintain normothermia since hypothermia can lead to cardiac arrhythmias, hypotension, coagulation problems and sluggish blood flow. Heated surgery tables, warm water circulating blankets, fluid warmers, warm air circulating blankets, oat bags, warmed bubble wrap, and warmed the inspired air are all measures that can be taken to try and maintain the patient's body temperature. In the author's experience once the patient is hypothermic it is very difficult to raise the temperature while the patient is anesthetized; therefore, measures to maintain normothermia should be taken while the patient is being clipped and prepped. In addition patients in radiology lose a great deal of heat and attempts should be made to keep the patient warm while radiographs are being taken. Warming the inspired air in the author's experience is the most effective means of maintaining normothermia and can be used to effectively rewarm cold patients. Fluids used to lavage body cavities or large wounds also should be warmed to body temperature.

Monitoring Under Anesthesia

Monitoring the critical patient under anesthesia is vital in order to minimize morbidity. Although many pieces of equipment are available to help with monitoring the patient under anesthesia, nothing replaces the human being. Monitoring should be done every 5 minutes to a maximum of 15 minutes in the stable patient.

Respiratory rate, chest excursion, mucous membranes colour, pulse oximetry and capnometry should be used to assess the respiratory and ventilatory status of the patient. Blood gases should be run if there are any concerns with pulse oximetry or capnometry measurements. Heart rate, lingual pulse strength, capillary refill time, central venous pressure (or jugular distention and filling), blood pressure (preferably by Doppler), and an electrocardiogram (ECG) should be used to assess the cardiovascular status of the patient. If a urinary catheter is not present and abdominal surgery is being performed the surgeon should be asked to monitor the urinary bladder for signs of urine production. This helps confirm adequate blood pressure and circulating blood volume. An esophageal stethoscope can be very useful for monitoring lung sounds as well as heart sounds under anesthesia since electrical equipment may fail or be interfered with by surgical equipment such as drills and electrocautery. Temperature monitoring is extremely important.

Electrocardiography

Electrocardiographic monitoring records the electrical activity of the heart only and the presence of normal complexes does not necessarily indicate normal cardiac function. Trends in the frequency and severity of any arrhythmias as well as response to antiarrhythmic therapy can be monitored. Waveform alterations such as changes in the ST segment and T wave configuration can be used to determine the possible presence of myocardial ischemia. Abnormalities in the conduction system consistent with myocardial disease, as well as pericardial effusion frequently can be determined.

Pulse Oximetry

Pulse oximetry measures the saturation of hemoglobin, which correlates with oxygen content in the blood. A probe, which emits red and infrared light, is attached to the patient. Saturated hemoglobin absorbs more infrared light than desaturated hemoglobin, which absorbs more red light. A photodetector receives the light signal and the percentage of saturated hemoglobin is displayed. Tongue clips provide the most accurate readings. Tongue clips will often apply sufficient pressure to the tongue to interfere with circulation and cause inaccurate readings. This can be corrected by moving the clip at regular intervals to a slightly different location on the tongue an ensuring the tongue remains moist. Poor readings will result from poor pulsatile flow, thick tissue between the light emitter and receiver, movement, pigmentation and strong overhead fluorescent lighting. Oxygen saturation reaches 100 percent at an arterial pressure (PaO2) of about 95 mm Hg. The PaO2 should be 4.5-5 times the fraction of inspired oxygen (FiO2). Therefore with an FiO2 of 1 (100 percent O2 which is the concentration given during anesthesia) the PaO2 should be 450-500 mm Hg. The SaO2 will read 100 percent from a PaO2 of 500 mm Hg to below about 95 mm Hg. This makes SpO2 a very inaccurate means of monitoring oxygenation in the patient that is receiving 100 percent O2 but can be a very useful monitor in the patient breathing room air or on supplemental oxygen support. It is always indicated to continue to monitor pulse oximetry in an anesthetized patient once the oxygen has been turned off. Supplemental oxygen should be provided if there are signs of desaturation on room air. Cyanosis, which correlates with a PaO2 of approximately 60 mm Hg, is equivalent to an SpO2 of approximately 90-92%.

Capnometry

Capnometry is a noninvasive means of assessing arterial carbon dioxide tension (PaCO2) and is the only noninvasive way of assessing ventilation. A detector is inserted between the endotracheal tube and the anesthetic tubing which is then connected to the capnometer via tubing. The capnometer analyzes the carbon dioxide level in the air in the tubing and provides a digital or waveform readout as well as a numerical analysis. Waveform display always is preferred since it allows for early detection of changes in ventilation, including increasing lung stiffness, chronic obstructive airway disease, and problems with the fresh gas supply (i.e., exhausted CO2 absorber). Assuming normal perfusion to the lungs and no airway obstruction, end-tidal carbon dioxide (ETCO2) correlates with PaCO2. The ETCO2 levels generally will be about 5 mm lower than PaCO2. If pulmonary blood flow is inadequate the CO2 levels will be very subnormal (< 15-18 mm Hg). The ETCO2 generally should remain between 25-35 mm Hg, although this number may need to be adjusted based on blood gas results.

Not infrequently, dogs and cats will present with a history of an acute onset of clinical signs related to the abdomen. History may include signs of lethargy or depression, anorexia, retching, vomiting, diarrhea and abdominal distention. These patients are usually painful on abdominal palpation, although pain may not be clinically evident if the patient is severely depressed. They often exhibit signs of some degree of cardiovascular shock. Some of these patients can, and should be managed medically, and some require emergency surgery (within minutes to hours of presentation); therefore, it is important to be able to determine rapidly whether or not surgery is indicated. If there is any doubt it may be better to perform an exploratory laparotomy rather than wait and have the patient deteriorate.

Acute abdominal conditions requiring emergency surgery include condition such as trauma-related disease (persistent hemorrhage, penetrating wound to hollow viscus, ruptured urinary bladder), gastrointestinal obstruction (foreign body, neoplasia), gastrointestinal accident (gastric or intestinal torsion or volvulus, intussusception), peritonitis, liver lobe torsion, splenic torsion, abdominal masses, and vascular accident. This seminar will focus on more common abdominal emergency conditions - primarily those affecting the gastrointestinal tract.

As with non-surgical abdominal conditions these patients may present in a stable condition or may be very unstable depending on the severity of the underlying condition. A full physical exam is indicated starting with a primary survey and followed by a secondary survey. As with any other medical problem resuscitation should be started as indicated.

In some cases the need for surgical intervention is obvious (gastric dilatation and volvulus, intestinal obstruction, ruptured splenic masses, etc.); however, in some cases the decision to go to surgery may not be so straightforward. Other indications for surgery include some of the following. Trauma patients with ongoing hemorrhage that are not stabilizing with conservative care should go to surgery. Patients with evidence of peritonitis based on abdominocentesis or abdominal lavage should go to surgery. Some patients in shock may not be painful on presentation. As they are being resuscitated these patients can often become excruciatingly painful. The clinician should have a very high index of suspicion that these patients may require surgery and serial abdominal exams (physical, ultrasonographic and cytological) should be performed with this in mind.

Diagnostic Peritoneal Irrigation and Lavage

Diagnostic peritoneal lavage is used to help in the diagnosis of intraabdominal conditions. Results of lavage fluid examination are extremely useful for determining the need to exploratory surgery in cases where the diagnosis is uncertain. Diagnostic peritoneal lavage allows for accurate evaluation of hemoabdomen and peritonitis. Four quadrant abdominocentesis can yield a high percentage of false negative results unless there is a large amount of fluid present whereas diagnostic peritoneal lavage has an extremely low incidence of false negative results.

To perform a diagnostic peritoneal lavage the animal is placed in left lateral recumbency. This keeps the spleen away from the midline. Ideally the urinary bladder is emptied. A clip and surgical prep is performed of a 4 cm square area 2 cm distal to the umbilicus on the midline. A local block is placed in the skin and peritoneum. Sedation is only used if absolutely necessary. Surgical gloves are worn and ideally a drape is placed. A stab incision is made in the skin 2 cm caudal to the umbilicus either on the midline or just lateral to the midline. A multi-holed catheter is inserted into the abdomen. In cats and small dogs an 18g 2 inch (5 cm) catheter is ideal. In medium and larger sized dogs a 16g or 14g 5.25 inch (13 cm) catheter is inserted. Side-holes can be added using a #15 scalpel blade. Alternatively a commercial diagnostic peritoneal lavage catheter can be used. The catheter is inserted in a caudal direction. If fluid is retrieved a sample is collected aseptically for analysis. To complete the lavage 20 ml/kg of warm (body temperature) isotonic crystalloid fluid is infused. Since this will increase pressure on the diaphragm, the respiratory rate and effort should be watched closely and fluid infusion stopped if the animal starts to show signs of respiratory distress. Once the fluid has been infused the animal is gently rotated to mix the fluid around and then fluid samples are collected for analysis. A packed cell volume, protein level, white blood cell count and microscopic examination of the fluid should be performed. Cultures are indicated if bacteria are present. Blood chemistries such as amylase, lipase, alkaline phosphatase and bilirubin can be analyzed. Levels that are higher than serum suggest pancreatitis, intestinal disease and biliary disease respectively. High potassium levels are consistent with urinary tract rupture. Urea nitrogen levels will equilibrate rapidly between the serum and peritoneum but in an acute bladder rupture the peritoneal level will be higher than serum. If the catheter is being used to monitor intraabdominal hemorrhage it can be sutured in place and serial samples can be taken or serial lavages can be performed. If the catheter is removed a dressing is placed over the incision. A suture or staple can be placed if desired.

Diagnostic peritoneal irrigation can be performed much more simply but studies have not been performed to determine the incidence of false negative results. To perform a diagnostic peritoneal irrigation the patient is place in lateral recumbency. Two areas are surgically prepped - one on the right lateral and one on the left lateral abdomen (upper and lower side). An 18g needle is inserted in the upper side and lower side and fluid is infused through the upper needle. The infusion is continued until fluid is seen flowing from the down-side needle. This fluid is collected for analysis as for a lavage.

Overview of Surgical Treatment

Surgical treatment is indicated in many acute abdominal conditions. The sun should never rise or set on an esophageal or gastrointestinal obstructions, ischemic abdominal diseases (organ torsions, vascular accidents) or peritonitis.

The patient should be closely monitored while it is being resuscitated and prepared for surgery. Vital signs, blood pressure, central venous pressure, electrocardiogram, and pulse oximetry should be evaluated as frequently as continuously to as infrequently as every 30-60 minutes if the patient is stable. All numbers should be recorded since often the trend of change is more important than the absolute numbers.

A team of a minimum of 3 people - surgeon, assistant surgeon and anesthetist/circulating nurse is very important in the management of these patients. Balanced anesthesia with close monitoring of blood pressure and ventilation is essential. A Doppler blood pressure monitor for indirect pressure monitoring is very useful for this purpose and is strongly recommended. Many of these patients do not ventilate well under anesthesia and may require hand ventilation or preferably the use of a mechanical ventilator. Due to the fact that a hollow viscus may be incised or the gastrointestinal tract may be compromised at the time of surgery, broad-spectrum antibiotics must be started prior to beginning surgery. A nasogastric tube should be placed in all larger dogs for postoperative decompression and early enteral feeding. A nasogastric tube should be placed also in dogs or cats with evidence of gastroparesis. A jejunostomy feeding tube should be placed in all patients with upper gastrointestinal surgery (including hepatobiliary and pancreatic) if there are any concerns that enteral nutrition will not be able to be started within 24-36 hours. The use of multiple litres of lavage of the abdomen with warm sterile saline is recommended prior to closure. Closure of the linea alba is performed using a simple continuous pattern of polypropylene or polybutester in the external rectus sheath. The peritoneum should not be closed.

Open Abdominal Drainage

Open abdominal drainage should be instituted in the severely contaminated or infected abdomen. The abdomen is lavaged extensively. The falciform ligament is removed. A continuous closure of the linea alba is started using large monofilament nonabsorbable suture. The suture is left loose allowing a gap of approximately 1-2 cm. This allows for fluid to drain but prevents dehiscence. The abdominal incision is covered with sterile highly absorbent towels or laparotomy pads followed by an abdominal bandage. In order to facilitate changing the abdominal dressing it can be held in place by umbilical tape that has been laced from one end of the incision to the other. Suture loops can be tied on either side of the abdominal incision (approximately 4-5 cm from the edges of the incision. The towels or laparotomy pads are placed and then umbilical tape is laced in between the suture loops to hold the dressing in place. When it comes time to change the dressing the umbilical tape is untied, the dressing is easily removed, and then a new dressing is placed. A urinary catheter and closed collection system is indicated in the male dog.

The dressing should be changed whenever it strike-through is evident. This usually occurs twice a day but in highly inflammatory conditions the dressing may need to be changed every 4 to 6 hours. This must be done aseptically although sedation is not usually required. Cytology of the abdominal fluid should be assessed on a daily basis for bacteria and neutrophils. The abdomen should be closed when evidence of infection has resolved or the effusion has minimized. This usually takes 3 to 5 days. At the time of closure reexploration is not necessary unless the original site of disease or injury needs to be reexamined. The suture in the linea alba is cut in the middle and pulled tight and tied. The subcutaneous space is lavaged but not closed. Normally granulation tissue has formed by the time of closure and debridement should only occur if there is concern for the viability of the tissue. The skin is closed normally and a dressing is placed over the surgical incision.

Open abdominal drainage is associated with a number of complications including significant hypoproteinemia necessitating plasma transfusions, electrolyte abnormalities, hypothermia, ascending infection, evisceration and additional costs associated with bandage changes and a second surgery.

Closed Abdominal Drainage

Closed suction drainage may provide an alternative to open abdominal drainage. After irrigation closed suction drains are placed in the cranial abdomen and the abdomen is closed. The drains are left in place until the amount of fluid being produced is within physiologic limits and the fluid cytology shows no signs of active inflammation or infection. Recent reports as well as the author's personal experience suggest this method of drainage is effective and minimizes patient morbidity.

Acute Abdominal Surgical Emergency Conditions of the Gastrointestinal Tract

Foreign Bodies

Foreign bodies are one of the most common causes of vomiting in the young dog and cat, however, dogs and cats of any age can ingest foreign material. Fortunately many foreign bodies pass or are vomited without serious consequence but frequently these materials will cause a partial or complete obstruction of the gastrointestinal tract and surgical intervention is required is remove the material.

Esophageal Foreign Bodies

Esophageal foreign bodies are sometimes dealt with in a different manner from gastrointestinal foreign bodies and so will be dealt with separately.

History and Clinical Signs:

History is very important in the diagnosis of an esophageal foreign body. The dog may present with signs of drooling, excessive swallowing, dysphagia and apparent vomiting (which on closer questioning will be determined to be regurgitation). Dogs with an upper or mid esophageal foreign body may present with signs of respiratory distress as the foreign material may be compressing the trachea. Harsh lung sounds may indicate aspiration pneumonia.

Diagnosis:

Some foreign bodies may be palpable. Radiographs and esophagoscopy can then be used to locate the material if it is not readily visible. Barium should not be used if a perforation is suspected but rather a low osmolarity nonionic contrast material should be used.

Blood tests should include electrolytes, a blood gas, and a complete blood count with manual differential.

Treatment:

Dehydration and perfusion should be corrected prior to anesthesia and antibiotics started. Suctioning any esophageal fluid or contrast material will aid in observation and removal of the material as well as in the prevention of aspiration pneumonia. General anesthesia should be used and a cuffed endotracheal tube must be in place. The foreign body can be removed by the oral route if it can be reached and easily extracted. This can generally be done using a rigid endoscope and a "mechanics helper" or mare uterine biopsy forceps. Often additional lubrication with K-Y jelly and water will need to be added using a relatively stiff polyethylene catheter with its tip placed at the junction of the foreign body and the esophageal mucosa. By gentle manipulation after lubrication the foreign body is brought close to the end of the rigid endoscope and all 3 (foreign body, grasper and endoscope) are pulled out together. Flexible endoscopy also can be used to retrieve esophageal foreign bodies but can me more difficult since it is often difficult to dilate the esophagus. If this method is used the animal should be monitored closely for gastric overdistention which can easily occur secondary to air insufflation. If the foreign body is still stuck then surgery will be required. A gastrotomy may be used on many occasions for removal of lower esophageal foreign bodies however the surgeon must be prepared to do a thoracotomy and an esophagotomy in these cases.

If an esophagotomy is performed the incision should not be placed over the foreign body if at all possible unless the plan is to resect the damage esophageal tissue. If the material has caused a perforation the approach should be on the side of the perforation and all necrotic material must be debrided. A simple interrupted closure of both the mucosa and muscularis is generally accomplished with 3-0 to 4-0 polypropylene on a taper point needle. Resection will rarely be required if the foreign body is removed before circumferential necrosis occurs. A small flexible esophagostomy tube (with its tip distal to the surgery site) or gastrostomy tube is recommended to be placed post esophageal surgery to be used for feeding and allow the esophagus to rest.

Gastrointestinal Foreign Bodies

History and Clinical Signs:

History from an owner is the most useful factor in early diagnosis of a foreign body. Early signs of a gastrointestinal foreign body include nausea and vomiting and possible inappetance. Vomiting usually persists until the material has passed, been vomited or is removed. The character of the vomiting may assist in diagnosing the location of the problem and the degree of obstruction. Abdominal pain may or may not be present again depending on the duration of the problem and degree of obstruction.

Diagnosis:

The gastrointestinal foreign body may be directly palpable on physical examination. Abdominal pain is a warning sign and splinting may indicate the presence of a surgical disorder. Survey radiographs may reveal radioopaque foreign bodies and an abnormally gas distended loop of bowel may indicate an obstruction. A barium series may be required to identify the presence of the material. A loss of detail on the x-rays suggests the possibility of peritonitis and a diagnostic peritoneal lavage for examination for white blood cells, plant material and bacteria is immediately indicated. Blood tests should include electrolytes, a blood gas, a complete blood count with manual differential, and blood chemistries. If there is a concern the dog may have peritonitis or be developing SIRS then coagulation parameters (platelet estimate and a prothrombin time, activated partial thromboplastin time or a minimum of an activated clotting time) should be obtained as this patient will be at risk for disseminated intravascular coagulation.

Treatment:

The patient with a foreign body may present in a stable condition, in hyperdynamic shock or in decompensatory shock. Fluid therapy should be guided by the status of the patient. Those that are stable can be rehydrated more slowly. Those in shock will require rapid volume replacement with crystalloids and colloids. It is possible the critical patient may not be able to be completely stabilized until it is taken to surgery. Patients with gastric outflow obstructions must be resuscitated with 0.9% saline in order to be able to normalize their electrolytes and blood gas status.

Surgical removal is indicated in the vast majority of these cases. Occasionally in some patients rehydration will "relubricate" the bowel and allow the material to pass but this is the exception rather than the rule. In the critical or unstable patient surgery may be required rapidly as pressure necrosis could lead to bowel perforation. It is best, by far, to 'look' early, even if there is only a slight chance of a foreign body.

Once the foreign material is located the affected area should be packed off with moistened laparotomy pads or towels. If a gastrotomy is indicated 2 stay sutures should be placed to help retract the stomach. If no assistant is available these stay sutures can be anchored to the skin or drapes using towel clamps. A gastrotomy should be performed in a relatively avascular area of the stomach. An enterotomy should be performed on the antimesenteric border. If bowel viability is questionable a resection should be performed. Viable gut should be pink and warm with an intact blood supply, and should contract when gentle digital pressure is applied. All exposed tissues must be kept moist to prevent adhesion formation and inflammation. After removal of the foreign material the luminal fluid at that area should be evacuated as this may contain a high concentration of bacterial organisms and enterotoxins. The submucosa must be incorporated in each suture to ensure safety of the closure. The stomach should be closed in two layers. The enterotomy should be closed such that the lumen diameter is not compromised. Wrapping the omentum around the surgical site will aid in healing. The abdomen should be completely explored prior to closure. Gloves and instruments should be changed prior to closure

Gastric Volvulus and Dilatation (GDV)

History and Clinical Signs:

Commonly affecting the large breed deep chested breeds gastric dilatation and volvulus syndrome has the potential to be a life threatening problem. Progressive gastric distention leads to pressure on the vascular system especially the venous system compromising venous return to the heart thus leading to inadequate preload and shock secondary to inadequate stroke volume. Pressure on the diaphragm caused by a progressively dilating stomach may compromise lung expansion and lead to ventilatory compromise. Vascular compromise of the circulation to the stomach itself may lead to tissue ischemia, release of endotoxin into the circulation and ultimately to the release of cytokines and SIRS.

Diagnosis:

Diagnosis is commonly made by observing a dog that is restless, attempting to retch non-productively and perhaps has rapid abdominal distention. Due to the fact that the GDV mainly occurs in the deep chested dog the abdominal distention may not be evident until late in the disease. In early cases the gas distended stomach may be detectable on percussion of the cranial abdomen. On examination the dog may be in hyperdynamic shock or may be in a stage of decompensatory shock. As such findings are variable from tachycardia, tachypnea, bounding pulses and injected mucous membranes to collapse, respiratory distress, weak thready pulses.

Blood tests should include electrolytes, a blood gas, a complete blood count with manual differential, and blood chemistries. If there is a concern the dog may have peritonitis or be developing SIRS then coagulation parameters (platelet estimate and a prothrombin time, activated partial thromboplastin time or a minimum of an activated clotting time) should be obtained as this patient will be at risk for disseminated intravascular coagulation.

Treatment:

Immediate treatment should consist of oxygen if the dog is showing any signs of shock, and volume replacement with crystalloids and synthetic colloids started. An electrocardiogram should be monitored as these dog are prone to ventricular arrhythmias. The stomach should only be decompressed after volume replacement has been started due to the potential for worsening the hypovolemic shock. Rapid onset corticosteroids are usually given at shock doses (dexamethasone sodium phosphate at 4-8 mg/kg iv or methylprednisolone sodium succinate at 15-30 mg/kg iv) and broad-spectrum antibiotics started. A right lateral radiograph should be taken. On occasion the volvulus will not be evident on the right lateral in which case if there is a high index of suspicion a left lateral radiograph should taken. A characteristic shelf sign with compartmentalization supports a diagnosis of a gastric volvulus. Coagulation should be monitored as these patients are at risk for disseminated intravascular coagulation. Blood pressure should be monitored.

The dog ideally is taken to surgery as rapidly as possible for derotation and a gastropexy. Gastric lavage can be performed prior to, or during surgery; however it should be remembered a stomach tube can be passed on a twisted stomach. It is also possible to pass a stomach tube through the wall of an ischemic stomach and excessive force should not be used.

The type of gastropexy has not been shown to make any difference in outcome. The goal should be to perform a gastropexy that is secure and takes as little time as possible. An incisional gastropexy fits these criteria in the authors' hands. Care should be taken with a circumcostal gastropexy to avoid creating an iatrogenic pneumothorax. A gastropexy incorporated into the closure of the linea alba is not recommended due to complications that can develop if subsequent abdominal surgery is ever required.

Gastric tissue should be resected if it is not viable (black or green in colour, no evidence of bleeding when incised, and areas that appear to be close to perforating). This can be done with stapling equipment or manually. If a gastric resection is performed it is recommended that a gastrostomy tube be placed (through the incisional gastropexy) to allow for suction of fluid and blood clots. In all other GDV patients a nasogastric tube should be placed for postoperative decompression.

If a splenic torsion is present in conjunction with the gastric torsion the spleen must be removed without derotating the pedicle to avoid complications from severe reperfusion injury.

Intestinal "Accidents"

Other intestinal disorders requiring rapid surgical intervention include intestinal intussusception and mesenteric volvulus.

History and Clinical Signs:

These patients if seen early in the disease process may only present with signs of not acting normally with possible restlessness and nausea. Late in the disease they may present with a history of vomiting, diarrhea (which may or may not be hemorrhagic), abdominal distention and possible abdominal pain.

Diagnosis:

Palpation may reveal an intussusception however in the case of a sliding intussusception that may reducing itself intermittently diagnosis can be challenging. These animals are generally painful on abdominal palpation and significant splinting may be present. Gut sounds may or may not be present. Survey radiographs may reveal gas distended loops of bowel; however, in some cases a barium series may be required. Ultrasound can also be used to diagnose intussusception. Surgical exploration must be done as soon as possible. In the case of a mesenteric volvulus endotoxic shock commonly leads to death and surgery is indicated immediately upon presentation if the animal is to have any hope of survival.

Blood tests should include electrolytes, a blood gas, a complete blood count with manual differential, and blood chemistries. If there is a concern the dog may have peritonitis or be developing SIRS then coagulation parameters (platelet estimate and a prothrombin time, activated partial thromboplastin time or a minimum of an activated clotting time) should be obtained as this patient will be at risk for disseminated intravascular coagulation.

Treatment:

As with the patients with intestinal obstructions or GDV these patients must be resuscitated with oxygen, crystalloids and colloids. Close monitoring is required as these patients may have a complicated preoperative, operative and postoperative course. Surgery is required for these patients as soon as possible. Most frequently resection will be required. If more than one intussusception has occurred enteroplication will be required in many cases to prevent recurrence.

Pancreatitis

History and Clinical Signs:

Spontaneous pancreatitis appears to have a number of mechanisms that play a role as "inciting causes". These include obesity, malnutrition, hyperlipidemia or hyperlipoproteinemia, drugs, trauma, complication following splenectomy, post pancreatic manipulation biopsy or resection of pancreatic neoplasia, hypercalcemia, duct obstruction duodenal reflux and duct obstruction, cholangiohepatitis and hepatic lipidosis in cats and miscellaneous diseases (intervertebral disc disease, scorpion stings, uremia, etc.)

Animals with acute pancreatitis are usually presented because of depression, anorexia, vomiting, and in some cases, diarrhea. In severe cases associated shock and collapse may be present. In other cases the signs they have are very vague to almost nonexistent. Cats with mild pancreatitis often present with a vagus history of being inappetant. Some animals with severe pancreatitis will exhibit signs of cranial abdominal pain and even a "praying" position. Pain may or may not be evident. Patients in shock may not show any signs of pain until perfusion is restored with fluid therapy.

Diagnosis:

Diagnosis is often based on clinical suspicion since laboratory, radiographic and ultrasonographic findings can be inconclusive. Results often relate to the degree of systemic illness. Abnormal white blood cell counts, left shift, and elevated pancreatic enzymes and liver enzymes may be present but the absence of these abnormalities does not rule out pancreatitis.

Radiographs often reveal increased density, diminished contrast, and granularity in the right cranial quadrant, displacement of the stomach, widening of the "angle" between the antrum and the descending duodenum, displacement of the descending duodenum to the right with gas patterns in the duodenum. The subjective loss of visceral detail in the cranial abdomen is probably the most common radiographic sign observed. In cats the loss of detail associated with pancreatitis is more commonly seen on the lateral view immediately caudal to the stomach.

Ultrasonic interrogation of the cranial abdomen will also be helpful in some cases but is fairly operator (and to some extent machine) dependent. The appearance of mass effect within the pancreas as well as cystic areas, abscess (complex cystic regions), edema, and free intraabdominal fluid are occasionally observed. If the pancreas can be visualized easily it is abnormal in most cases. Caution should be exercised in ruling out pancreatitis on the basis of a normal ultrasound exam. Diagnostic peritoneal lavage can be very useful in diagnosing and treating this condition.

Treatment:

As with all critical patients they must be resuscitated with oxygen, crystalloids and colloids. Close monitoring is required as these patients may have a complicated preoperative, operative and postoperative course. Surgery is recommended if the following findings are noted on DPL: (need at least two of the criteria fulfilled):

• WBC count of the lavage fluid...> 20,000, increasing with repeated lavage
• Differential of the lavage fluid... predominant cell is neutrophil (>90%), segmented
• Cytology of the lavage fluid.......... intracellular bacteria, hypersegmented and vacuolated WBC
• Amylase of the lavage fluid.......... > 200 IU activity, increasing with repeated lavage
• Lipase of the lavage fluid.......... greater than the lipase in the serum, increasing when repeated
• Ultrasonographic evidence of a mass effect of free fluid in or around the pancreas are indications for surgery as is evidence consistent with biliary duct obstruction. Recurrent bouts of pancreatitis and uncontrollable pain are also indications in the author's opinion for exploratory surgery

1. Explore the entire abdomen to find all pathology present and to take appropriate tissues for histopathology and culture. Pancreatic biopsies are taken using a ligation method. 4-0 polypropylene is used to "rope" a small wedge of tissue and tightened. The tissue trapped outside the ligature is removed carefully with a # 11 blade.
2. Debride and remove all necrotic and suppurative tissue. Frequently the pancreas will appear white, necrotic, firm and suppurative. Incisions should be made over these areas to open the capsule and a small strabismus scissors is used to resect the necrotic suppurative tissue. Direct irrigation with a syringe filled with warm saline connected to a 21 ga needle and suctioning with a Frasier suction tip will be required for each area of suppuration. In some cases large peripancreatic abscesses and necrotic tissue will require resection and placement of suction drains. Resection of pancreas is occasionally necessary if its entire thickness is necrotic.
3. Ensure that obstructions of the duodenum and bile duct are not present. Resection of the duodenum should only be attempted as a last resort. If it is still viable a gastrojejunostomy can be done to relieve the proximal duodenal obstruction. A cholecystojejunostomy with a wide ostomy can be done for complete common bile duct obstruction if the gall bladder is viable.
4. Irrigate the entire abdomen until the effluent is clear and then dry it.
5. Place a 3.5 to 8 French jejunostomy tube for feeding. An alternative is a nasojejunal or a gastrojejunal catheter. Enteral nutritional support is key to recovery, especially in cats with concurrent hepatobiliary disease.
6. Place a gastrostomy tube for decompression or verify proper position of an NG tube placed for decompression.
7. Once the necrotic tissue has been debrided the abdomen should be extensively irrigated. As much as 10 L of saline may be needed. Traditional recommendations have included open abdominal drainage if suppurative peritonitis is present; however closed suction drainage may provide an effective alternative.

Introduction

Appropriate wound care provided in a timely manner can help prevent significant morbidity and mortality. The seriousness of wounds should not be underestimated and in most cases aggressive surgical treatment is indicated as soon as the patient is cardiovascularly stable.

First Aid Initial Stabilization

Evaluation of the patient should begin always with the ABC's (airway, breathing, circulation). The wound may be the obvious injury but it may be minor compared to an unseen injury such as airway disruption or pneumothorax. If the animal cannot breathe an airway will need to be established. In the case of severe oral trauma a tracheostomy may be indicated. If the patient is able to breath adequately but there is a significant amount of hemorrhage, the clinician may need to make a decision as to whether or not to anesthetize the animal and gain control of the airway since ongoing hemorrhage could potentially lead to an airway obstruction. Once an injured patient is intubated the lungs should be ausculted bilaterally to ensure air is moving though both lung fields. The patient who arrived unconscious and not breathing may have an avulsion of the distal trachea and unless the lungs are ausculted post intubation this may not be detected. Auscultation also will allow the clinician to assess the presence of a possible pneumothorax, hemothorax or pericardial tamponade. Intravenous catheters should be placed and fluids started if the patient is in shock. Analgesics are always indicated once the patient has been evaluated and resuscitation has been started.

Active bleeding from wounds will need to be controlled. Capillary oozing and most venous hemorrhage can be controlled with pressure bandages. Pressure should be applied as a temporary measure to control arterial hemorrhage but definitive control of arterial bleeding using a hemostat followed by ligation should be achieved as soon as possible.

The most important rules to follow during first aid care of wounds are to keep the wound moist and to keep it as clean as possible. All wounds should be covered as soon as possible with sterile water soluble lubricant followed by sterile gauze to prevent further contamination and injury. Gloves should be worn whenever wounds are evaluated since many wounds are contaminated but not infected when the animal enters the hospital. Many infections come from the hospital environment, both from the floors and cage surfaces, as well as the nurses' and doctor's hands. Placing sterile water-soluble lubricant in the wound helps keep it moist. This is important since desiccation impairs wound healing. Alternatively a wet dressing made from sterile gauze soaked in 0.9% saline can be applied.

If missiles are present (such as arrows, large wood splinters etc.) they should not be removed. These objects may be tamponading a vessel and premature removal may cause life-threatening hemorrhage. Missiles should only be removed under controlled surgical conditions.

If the wound is associated with a fracture then a padded bandage or temporary splint should be applied until the patient can be completely evaluated. This helps prevent further mechanical injury to the tissues from the tearing effects of bone fragments. It also helps to prevent further injury to the bone and provides comfort to the patient. Radiographs can be taken through most bandage materials' therefore, an attempt always should be made to stabilize fractures prior to taking radiographs.

Assessment

Proper assessment of most wounds requires some form of analgesia at a minimum and may require general anesthesia. The injury is painful and even if the patient is stoic attention should be paid to providing adequate analgesia. Not only is pain detrimental to the overall well being of the patient but also it is detrimental to the healing process. Catecholamine release can lead to vasoconstriction and poor flow to the wound area. Initial analgesia can be provided most effectively using intravenous opioids and/or local anesthetic agents.

All wounds should be widely clipped in order to be able to assess them properly. This includes abrasions and bruises. Frequently, animals that are bitten have been impaled by both upper and lower teeth. If bite marks are seen only on one side of the limb or trunk then the other side should be shaved to search for the wound.

The type of diagnostic tests required will be dictated by the type of wound. Thoracentesis to check for air and blood should be performed in every patient that has a wound over the thoracic cavity. Radiographs are indicated in any wound that may be associated with an open fracture, joints, and thoracic or abdominal cavities. Diagnostic peritoneal lavage should be performed in cases where the wound is over the region of the abdominal cavity and it is not certain if the abdomen was penetrated or not. Laboratory tests again will be dictated by the status of the patient and the location of the wounds. Since general anesthesia is required to treat most penetrating wounds and many full thickness skin lacerations, appropriate tests should be performed to ensure the animal can tolerate anesthesia. Whenever there are concerns for significant hemorrhage (based on history), a packed cell volume and total protein always should be performed to assess for the presence of anemia and/or hypoproteinemia. Patients with extensive wounds or concerns for a coagulopathy should have coagulation parameters including platelet numbers assessed.

All penetrating wounds should be surgically explored. This is especially important in the case of bite wounds since the teeth may only have made a puncture mark in the skin but as the animal was shaken there may have been extensive tearing damage done to underlying tissues. Wounds that penetrate the abdominal cavity may have caused hollow or solid organ damage.

Surgical Management

The goal of surgical management of wounds should be to explore and remove any foreign material, control hemorrhage, and remove necrotic tissue. Many wounds will require the use of general anesthesia; however, superficial wounds that do not require extensive debridement can be managed under sedation and local anesthesia.

The wound should be widely clipped and surgically prepped. This is very important since the extensive nature of the trauma can be easily underestimated based on external visualization.

Surgical Prep Solutions

The primary surgical prep solutions contain chlorhexidine, povidone-iodine or Techni-CareÒ (Care-TechÒ Laboratories, St. Louis, MO). All are broad spectrum. Chlorhexidine has a rapid kill (90% within 30 seconds) and because it binds to keratin it has residual effect. It is not inactivated by the presence of organic material as povidone-iodine is. The major problem in critical care units is that Pseudomonas can develop resistance to chlorhexidine. It is toxic to certain tissues and should not be used in and around eyes or ears. Povidone-iodine is available in scrubs and solutions. Scrubs contain detergents and should never come in contact with eyes, subcutaneous tissues, etc. It is inactivated by organic material, including blood, and it requires prolonged contact (90% kill within 2 minutes) to be effective. Alcohol wipes should not be used in between application of povidone-iodine as it may reduce its effectiveness. It has been recommended that a scrub time of up to 5 to 7 minutes is required for both chlorhexidine and povidone-iodine. Techni-CareÒ is a surgical scrub (containing chloroxylenol and cocamidopropyl PG-dimonium chloride phosphate) that is reported to have a rapid kill (99.9% in 30 seconds). It is safe to use in wounds and on oral and ocular tissues. It contains substances that may actually aid in wound healing. It is a waterless scrub that may significantly reduce the hypothermia that can develop secondary to evaporative heat loss after using wet scrubs.

Wound irrigation

Wound and body cavity irrigation form an important part of any surgical procedures. "Dilution is the solution to pollution." Sterile isotonic solutions such as 0.9% saline, lactated Ringer's solution, Plasmalyte 148/Plasmalyte-A or Normosol-R are preferred for irrigation. Tap water has been used to irrigate wounds without complication; however, tap water is not ideal due to its hypotonicity. In large wounds effective irrigation with sterile isotonic solutions may be cost prohibitive, in which case irrigation with tap water may be appropriate. Antibiotics should not be added to irrigation fluids and extreme care should be exercised when adding disinfectants to irrigation fluids. Body cavities should be irrigated with sterile isotonic fluid only. Irrigation can be provided using mechanical lavage systems designed for wound irrigation or using a 35 ml syringe and an 18- to 19-gauge needle. Pressure generated by the irrigator should not exceed 7-9 PSI. Irrigation should not be done blindly or up into holes since this may force infection or foreign material further into the wound or potentially into healthy tissues. This can actually make the wound worse.

Wound Exploration

The skin should be incised in order to be able to visualize and assess the entire wound. Most mistakes in wound care are made from a lack of knowledge about the extent of the trauma because the wound was not adequately explored. Foreign material should be removed as it is encountered. Tissues should be debrided back to bleeding edges whenever possible using sharp dissection. This is especially important with fat and muscle. Bone and ligament should be removed if the surgeon is certain it is non viable but if there is any doubt the tissue should remain since removal may interfere with subsequent function of the affected area. Skin edges of wounds should be debrided using sharp dissection back to bleeding edges unless this might cause problems with wound closure. Scissors generally should not be used since they may cause crushing of the tissue, which can compromise circulation to the wound edges and cause problems with healing.

Hemostasis

Hemostasis generally is achieved by direct pressure, suturing of wounds (compression of vessels), electrosurgery, ligation of vessels, vascular clips, omental packing, use of superglue, use of hemostatic agents or removal of the organ that may be bleeding. There are numerous products available for hemostasis many of which are based on gelatin, fibrin, bovine thrombin, seaweed and a variety of other natural products that have hemostatic qualities.

Electrosurgery is indispensable for rapid and efficient control of hemorrhage in critically ill or injured patients who are predisposed to being anemic and have coagulopathies. It causes heat-induced protein denaturation and tissue coagulation and can be used to control hemorrhage from arteries up to 1 mm and veins up to 2 mm in diameter. Monopolar electrosurgery passes a current between the electrode through the patient to a ground plate. It requires a dry field as opposed to bipolar electrosurgery where the current passes between 2 electrodes. Thermal damage is a potential side effect of monopolar electrosurgery and to a lesser extent with bipolar electrosurgery that can lead to ischemia and delayed healing.

Wound Closure

Wounds should be irrigated again prior to closing the skin to remove any additional foreign material and blood. The presence of blood provides an ideal medium for bacterial proliferation. If there is any doubt about viability of tissues the wound should not be closed initially. Instead wet-to-dry dressings should be placed and the wound should be revaluated on a daily basis. Daily debridement should be performed as necessary until the health of the tissues is assured.

Infected wounds generally should not be closed but should be allowed to heal by second intention. Alternatively the wound can be left open until it is certain that the infection is resolved and then closed at a later date.

The amount of suture left in wounds should be minimized. Fine monofilament suture should be used in the repair of most wounds. Braided suture should be avoided in potentially infected wounds. Skin sutures should not be placed tightly since again this may compromise circulation. Wounds should not be closed under tension since this will compromise wound healing. Skin can either be mobilized by undermining of healthy tissues or grafting should be used as needed.

Closing Dead Space

Dead space can only be closed effectively using active suction drains or bandages. Both drains and bandages will help enhance wound healing and prevent seroma formation. Sutures can be used to approximate tissues but cannot close dead space. Using sutures to "close dead space" should be avoided since it can create compartmentalization and the amount of foreign material (suture) left in the wound is increased.

Drains

Two types of drains exist - passive and active. Passive drains such as Penrose drains allow wound exudate to drain by gravity or overflow. The most serious complication associated with Penrose drains is the risk of ascending infection and ideally Penrose drains should be covered with a sterile dressing. Active drains remove wound fluids by application of negative pressure. Fenestrated drains are attached to a suction bulb that is primed by removal of air. These are available commercially in sizes ranging from 4 to 20 Fr. A small suction drain can be made using a butterfly catheter and a vacutainer tube. The end of the butterfly catheter is cut off and multiple holes are made in the catheter. The drain is placed in the wound and the needle end is inserted into a vacutainer tube. Similarly a suction device can be made from a 12 or 20 cc syringe. The syringe is attached to a fenestrated butterfly or other catheter or tube that has been inserted in the wound. The plunger is pulled back about 50-75% of the way (until the desired level of negative pressure is achieved) and an 18 or 20 ga needle is placed through the plunger to hold it at that level. The hub of the needle rests on one side of the barrel of the syringe and the tip of the needle rests on the opposite side to prevent the plunger from sliding back into the barrel. The tip of the needle should be cut off or taped to prevent inadvertent injury from the needle.

Drain suction bulbs, syringes, or vacutainers are changed as necessary - usually 2-4 times per day. Drains are left in place until they are no longer functional or until they are no longer needed. Drainage will slow down within 72 hours in most wounds. If a large amount of dead space was created the drains may need to stay in place for up to 5-14 days.

Bandages

Bandages are designed to protect the wound and encourage wound healing. They can also provide support to underlying tissues and help improve patient comfort and mobility. Contaminated or infected wounds should have wet-to-dry dressings placed until the wound is clean. When wet-to-dry bandages are removed they will help mechanically debride remaining foreign material and necrotic tissue. These dressings should be compromised of wide-meshed gauze, which will entrap particulate matter, soaked in 0.9% saline.

Nonadherent dressings should be used in acute wounds that do not require further debridement, are not draining large amounts of fluids, or in wounds that are starting to heal. Nonadherent dressings can be divided into occlusive and semiocclusive categories. Semiocclusive dressings allow absorption of wound fluids into the intermediate layer but retain enough moisture to prevent desiccation of the wound. These include Telfa pads and also can be made from gauze impregnated with petrolatum or petrolatum-based antibiotic ointments that has been autoclaved.

Occlusive dressing are impermeable to wound fluids. These include films, foams, hydrocolloids and hydrogels. They help epithelialization of partial thickness wounds although their effect on full thickness wounds is less clear.

The intermediate layer of the bandage is designed to absorb wound fluids. The thickness of this layer depends on the wound itself. It is important to make it thick enough to avoid "strike-through" of wound fluids in between bandage changes. The outer layer should secure the other bandage layers and should protect the wound from external contamination from urine, feces and other fluids that could soak into the dressing. The outer layer is usually some form of tape - either elastic or surgical. It is important that this layer be placed securely enough to prevent slippage of the bandage but not too tightly so as to compromise circulation to the underlying tissues.

Large wounds may require excessive amounts of bandaging material. In these cases sterile towels can be used to cover the wounds. If wounds are superficial but need protection, application of a broad-spectrum antibiotic ointment to the wounds followed by towels may be all that is needed. Towels can also be used to hold inner layers of a bandage in place. Alternatively surgical paper drape material can be used as an outer layer. Both towel and surgical drape material can be secured using tape or safety pins.

Alternative Wound Management Options

There are a wide variety of alternatives available for wound care and more are being developed on an ongoing basis. Biological dressings such as products made from swine intestinal submucosa (BioSistÒ, Cook Veterinary Products) help replace tissue defects and encourage wound healing.

Sugar and Honey

Recently attention has been brought to the use of wound remedies that have been used for centuries - sugar and honey. Both of these topical treatments appear to have applications in veterinary medicine for treating wounds. Sugar and honey both have wound healing properties that include attraction of macrophages into the wound, reduction of edema and inflammation, and increase wound healing. In addition honey generates low levels of hydrogen peroxide and is acidic - both of which enhance bacterial killing.

Sugar can be used to treat degloving injuries, infected wounds, burns, and any skin injury where primary closure is not possible. The wound should be debrided and then a large volume of sugar is placed in the wound to ensure the osmolarity remains high enough within the wound to kill the bacteria. Approximately 1 cm of sugar is placed in the wound which is then covered with an absorbent dressing and a bandage. The bandage is changed once to twice daily. If there is no sugar in the wound when the dressing is changed then more sugar should be used in the wound.

Honey can be used to treat the same kinds of wounds as sugar. The wound is irrigated and debrided and then unpasteurized honey is placed in the wound. Strips of bandage material can be soaked in the honey prior to placing on the wound, or alternatively the honey can be placed in the wound and then covered with large amounts of absorbent bandage material.

Leeches

Medical grade leeches can be useful when arterial blood supply to an injured region is good but venous flow has been compromised leading to tissue congestion with secondary tissue compromise. Leeches produce salivary secretions that contain an anesthetic agent, a thrombin inhibitor that acts as an anticoagulant (hirudin), a histamine-like substance that causes vasodilation, and hyaluronidase. Each leech can draw up to 5 ml of blood from congested tissue.

Hyperbaric Oxygen

Hyperbaric oxygen chambers provide oxygen at high pressures (1.5 times atmospheric pressure), which increases the amount of dissolved oxygen into the blood. Hyperbaric medicine has been shown to be very effective at improving wound healing and may be a useful modality of the future.

Complications

Many animals that present to veterinary hospitals have wounds that are dirty and contaminated but not infected. Many wound infections are nosocomial and can come from the nurse and doctor's hands. Secondary problems with wound healing and patient morbidity may relate to inappropriate wound handling during the initial stages. Most problems with sepsis from wounds come from inadequate debridement of necrotic tissue. The presence of the necrotic tissue leads to a persistent inflammatory response, which can be overwhelming and can ultimately cause patient death.

Antibiotic therapy is indicated in infected wounds. Initially broad-spectrum antibiotics should be used pending culture results. The use of antibiotics in non-infected wounds is controversial. The use of broad-spectrum perioperative antibiotics is appropriate for most wounds.

Trauma Can Take You Anywhere

Successful management of the hemorrhaging trauma patient requires prompt recognition, aggressive treatment and diligent follow-up. The trauma patient must be assumed to have serious internal hemorrhage until proven otherwise. Initial resuscitation to normal levels must be completed within the first hour or "golden hour" of treatment.

Readiness and Resuscitation

Effective treatment of the trauma patient requires an appropriately equipped hospital and a trained team of doctors and nurses. Despite the fact that the hemorrhaging may be the most obvious problem in the trauma patient the ABC's of airway, breathing and circulation must be addressed first or possibly at the same time as hemorrhage is being controlled. The type of resuscitation of the trauma patient will depend on the amount of hemorrhage that has occurred or is still occurring. The goals of resuscitation are to provide adequate oxygen uptake in the peripheral tissues by improving circulation and oxygen carrying capacity of the blood. Supplemental oxygen should be provided, large bore catheters placed, and intravenous fluids should be given. Fluids should be given as rapidly as required to resuscitate the patient. The type of fluid administered will depend on the degree of trauma the patient has sustained. Those with mild shock and minor blood loss will probably respond well to intravenous crystalloids whereas those with severe hemorrhage will likely require whole blood or blood components, crystalloids and synthetic colloids (e.g. hemoglobin-based oxygen carriers, Hetastarch, Dextran 70). Crystalloids decrease blood viscosity and large volumes may potentially increase bleeding. Hemorrhage will need to be controlled before resuscitation can be considered complete. Initially temporary control of bleeding may be all that is possible however in certain cases definitive control will be required at the time of initial resuscitation. Recent, somewhat controversial studies have shown that "controlled hypotensive" resuscitation may lead to higher survival rates in the hemorrhaging patient. If the patient is hypotensive on presentation blood pressure should be raised above critical (mean of 60 mm Hg) but hemorrhage should be controlled prior to normalizing blood pressure. In controlled hypotensive resuscitation systolic pressure is kept between 80-85 mm Hg and 100 mm Hg and is aggressively controlled if systolic is greater than 130 mm Hg. It is felt that since fibrinous clot formation takes 20 to 30 minutes early increases in pressure lead to clot disruption.

Counterpressure

Counterpressure is most commonly provided externally; however, it can also be provided internally. The principal behind counterpressure is compression of blood vessels under the influence of the pressure and an increase in systemic vascular resistance. Since flow is proportional to the radius of the vessel raised to the fourth power a small decrease in vascular size can significantly influence flow.

External counterpressure to the hindlimbs, pelvis and abdomen can be an effective method of raising blood pressure and controlling hemorrhage from vessels under the wrap. It can be provided using commercial antishock garments, rolls of cotton and bandage material, or towels and duct tape. The pressure applied should be no more than 2 lb per square inch (40 to 60 mm Hg) and a hand should be able to be easily passed under the wrap once it is in place. (The goal is to avoid raising intraabdominal pressure above 20 mm Hg to avoid abdominal compartment syndrome.) Respiration must be closely monitored if the wrap encompasses the cranial abdomen as ventilation can be compromised especially if there is a diaphragmatic injury. The pelvic limbs must be included in the wrap if the abdomen is to be wrapped to prevent vascular occlusion of the caudal abdominal vena cava. Counterpressure should remain in place for a minimum of several hours and then be slowly removed and pressures closely monitored. If pressures drop by more than 5 mm Hg, removal is stopped, volume is infused and then removal restarted once the pressure has stabilized. If blood pressure cannot be maintained surgery is indicated.

Internal counterpressure can be used in abdominal hemorrhage by infusing 20 to 60 mL/kg of warm crystalloids into the peritoneal cavity to help tamponade the abdomen. Ventilation may be compromised by this procedure and should be monitored closely.

Medical vs. Surgical Management of Hemorrhage - When to Cut

It should always be assumed that the trauma patient has serious internal hemorrhage until proven otherwise. Surgery is indicated if vital signs are not stabilizing, the patient shows signs of relapsing into shock after initial resuscitation, or the abdomen is expanding. Those patients that present with a distended abdomen or those that develop rapid abdominal distention and signs of progressively deepening shock despite attempts at resuscitation do not present a diagnostic challenge. Surgery for abdominal hemorrhage requires an equipped surgical suite, good lighting, available blood products and a trained team of a minimum of 3 people - surgeon, assistant surgeon and anesthetist. The anesthetist is the most important member of the surgical team while the patient is unstable and hemorrhage is ongoing. The use of continuous positive pressure ventilation is vital to a successful outcome.

Virtually all penetrating abdominal wounds should be surgically explored. Laboratory tests such as a continually decreasing hematocrit (especially to 20% or below that is not responding to initial resuscitation and hemorrhage control methods), and a positive diagnostic peritoneal lavage (DPL) also indicate that surgery is required. Radiographic signs of pneumoperitoneum, diaphragmatic hernia, or mass effect indicate the need for exploratory surgery.

Ultrasonography is a rapid method of determining the presence of intraabdominal fluid however it does not easily indicate whether or not hemorrhage is ongoing. A sample of any free fluid seen should be taken and analyzed. Ultrasound is useful for determining the presence and extent of injury to solid organs. It also can be useful for interrogating the retroperitoneal space and the integrity of the urinary bladder. Human studies have shown that penetrating injuries to bowel and some other more minor injuries are better evaluated with DPL than ultrasound as ultrasound can lead to false negative results.

Diagnostic peritoneal lavage performed with a multi-holed catheter can be a valuable diagnostic tool for intraabdominal hemorrhage. Approximately 40 mL/kg of blood is required in the abdomen to detect abdominal hemorrhage on palpation or radiographically. Whereas abdominocentesis may be negative even with up to 50% of the blood volume in the abdomen, DPL is accurate over 95% of the time. Diagnostic peritoneal lavage involves the placement of a multiholed catheter into the abdomen through a stab incision made on the midline or just off the midline (to avoid the falciform fat) 2 cm caudal to the umbilicus. Approximately 20 mL/kg of warmed balanced electrolyte solution is infused into the peritoneal cavity. A sample is retrieved for hematocrit, total solids, chemistry and microscopic analysis. A lavage catheter can be left in place and samples removed at 5 to 10 minute intervals. A rising hematocrit by more than 5% is a strong indication for surgery as is analysis of DPL fluid suggesting hollow viscus injury.

"Bleeding somewhere, bleeding nowhere, check the retroperitoneum." Retroperitoneal hemorrhage may be detectable by observing an expanded or expanding retroperitoneal space on lateral x-ray. Most retroperitoneal hemorrhage can be managed medically however continued expansion of the retroperitoneal space despite the use of counterpressure may indicate the need for exploratory surgery.

Autotransfusion

Due to the limited availability of blood and blood products in most veterinary hospitals autotransfusion may be required in the severely hemorrhaging patient. If the trauma patient is bleeding into a cavity such as the thorax or abdomen an attempt should be made to collect the blood aseptically in case it is required for reinfusion. Blood should be collected into sterile containers with anticoagulant and administered with a filter. Ideally blood from the abdomen should not be used until it has been determined that there is no gross contamination from a ruptured bowel etc. In emergency situations the blood may have to be used without aseptic collection, knowing whether or not the blood is contaminated and delivered without a filter. Patients have survived under these conditions. It is better to be dirty and alive than clean and dead. Autotransfused blood lacks fibrinogen and platelets and disseminated intravascular coagulation is a common complication of large volume autotransfusion. Patients receiving large volumes of autotransfused blood should receive fresh frozen plasma concurrently. In addition, if the blood is being anticoagulated close attention should be paid to plasma calcium levels as they can drop significantly due to citrate binding.

Surgical Preparation and Initial Hemorrhage Control In Bleeding Cavities

Surgery for trauma patients requires good lighting, complete surgical packs, packing material (sterile towels, laparotomy pads and umbilical tape) and sterile bandaging material. Surgery packs for abdominal or thoracic surgery should contain routine instruments for major cavity surgery, Balfour retractors (can also be used in the chest), suction and red rubber tubing for forming vascular loops. Stapling equipment can also be very useful.

If there is time a complete surgical preparation of the patient is done. The chest should always be prepped in cases of abdominal exploratory in case of a need for a paramedian sternotomy. Both inguinal regions should also be prepped for possible vascular access to the femoral vessels. Rapid entry into the thorax or abdomen may need to be done without clipping or a surgical prep. In long-haired animals clippers may need to be used to expose the skin; otherwise the fur is just wetted down. If counterpressure is in place it should remain in place until the surgeon is ready to start making the incision. As the bandaging is removed the hands can be used to continue pressure.

If the patient is showing signs of rapid abdominal distension a rapid thoracotomy should be performed and the descending thoracic aorta crossclamped prior to entering the abdomen. In the less severely bleeding abdomen the incision is made into the cranial abdomen and expanded sufficiently to be able to place a hand into the abdominal cavity. The aorta is digitally compressed cranial to the cranial mesenteric artery. This can be located by locating the left kidney, moving medially past the left adrenal gland and compressing the aorta at that location. The abdomen is then packed with laparotomy pads or towels to help control bleeding and improve visualization of the bleeding injuries. The packs are then parted enough to be able to visualize where the abdominal aorta is being occluded. A window in the paraaortic fascia is made with curved forceps and umbilical tape or a small diameter feeding tube is passed around the aorta and held tightened as a loop with hemostats (Rumel tourniquet). The abdomen is suctioned and the packs removed one by one in a systematic fashion with bleeding being controlled by use of similar vascular occlusion. Suctioned blood should be collected in a sterile trap for autotransfusion purposes if necessary. The abdominal aortic occlusion is intermittently released as each quadrant is inspected after severe venous bleeding is ruled out. Definitive ligation of the vessels is performed after all the bleeding vessels have been temporarily controlled. Definitive ligation of all the bleeding vessels at the time they are isolated is a time-consuming process - time the patient often does not have. Packing will help control even major venous bleeding. If all bleeding cannot be definitively controlled the pads can be left in place and the abdomen temporarily closed and reexplored later once coagulopathies have been corrected. (See Damage Control below.)

General Principles of Surgical Hemorrhage Control

Direct pressure can be used to control hemorrhage from minor wounds or from more serious vascular injury until something definitive can be done. Electrosurgery (both unipolar and bipolar) is ideal for controlling hemorrhage from small vessels and is invaluable in trauma surgery. Lasers also can be used to control minor hemorrhage. Ideally bleeding from larger vessels should be controlled by direct ligation. Vascular loops composed of red rubber tubes, umbilical tape or similar narrow band material can be placed around a vascular pedicle or vessel and tightened to control bleeding while ligation is being performed. "Stick-ties" which involve placing a suture through tissue around vessels is a useful method of controlling hemorrhage from vessels that cannot be grasped easily with hemostats. In certain cases (bleeding superficial wounds, retroperitoneal hemorrhage) the arterial supply proximal to the wound and venous supply distal to the wound may need to be exposed and controlled prior to be able to visualize the bleeding vessels for direct ligation.

Hemostatic agents (i.e. hemostatic powders, gelfoam, thrombin - bovine collagen, avitine, C-stat). Can be very useful. Some of the newer hemostatic powders that are based on thrombin appear to be very effective. Products such as superglue have also been used to control hemorrhage in fractured livers and spleens. Omentum can be sutured into the oozing edges of injured solid organs to help control hemorrhage.

Definitive Liver Hemorrhage Control

Improved surgical exposure of the liver can be provided by placing a placing a laparotomy pad dorsal to the liver to help hold it up, extending the incision alongside the xiphoid or rarely by the use of a sternotomy or parasternotomy. Manipulation of the liver can lead to compromised venous return to the heart and central venous volume , Doppler flow sounds and arterial blood pressure should be closely monitored. Manipulation of the liver also can cause a vasovagal response and heart rates should be closely monitored.

Care of liver wounds can be aided by classifying the wound by 4 categories: superficial vs. deep, linear vs. fracture, central vs. peripheral and moderate vs. severe bleeding. In general deeper wounds, fracture wounds and central wounds have the greater potential for more severe bleeding. Superficial lacerations that are not actively bleeding do not require suturing. Superficial lacerations that are bleeding can usually be controlled with direct pressure for 10 to 15 minutes or suturing with 2-0 to 3-0 absorbable suture, usually using a mattress pattern. Other alternatives include the use of superglue, omental packing or hemostatic agents.

The finger fracture technique with the aid of the back of a scalpel handle can be used to dissect through the liver lobe exposing deeper vessels. Suction and irrigation also help with visualization of bleeding vessels. Curved hemostats or vascular clips are applied and the vessels ligated with hand ties of nylon or silk suture material. Suturing omentum around liver edges helps with hemostasis and helps prevent adhesions between other organs such as the stomach and the liver.

Devitalized tissue should be debrided to prevent abscesses. Crushed liver lobes can be removed by the finger fracture technique, ligation at the base of the liver lobe with a modified Miller's knot with slow release and flashing, or stapling. If available resection of devitalized fractured segments using laser and electrosurgery can be done.

In severe liver trauma the liver can be packed. If packing does not control the hemorrhage the liver edges can be sutured together with large chromic sutures, which may provide a tamponading effect. The hepatic artery can be temporarily occluded with a Rumel tourniquet or a bulldog or Serrafine vascular clamp. If bleeding persists then a Pringle maneuver using the fingers and thumb or a Rumel tourniquet is performed. This maneuver occludes the portal triad of the hepatic artery, portal vein and common bile duct. Intravenous antibiotics must be administered prior to vascular occlusion. The Pringle maneuver is usually performed for a maximum of 15 to 20 minutes. Portal compression should be released for 60 seconds every 10 minutes. Simultaneous occlusion of the cranial mesenteric artery should be performed to prevent acute portal hypertension.

If bleeding persists despite occlusion of the hepatic artery and portal vein then retrograde flow must be occurring from tears to the hepatic veins or the vena cava. In these cases the prognosis is very poor. Life-threatening exsanguination is usually due to a laceration in the central branch of the portal vein, the hepatic artery, the hepatic veins, the retrohepatic vena cava or a deep laceration of the hepatic parenchyma.

Subcapsular hematomas should be managed after observation for continued expansion or presence of devitalized tissue. Either of these findings indicates the need for surgical exploration; if not the hematoma is left alone.

Splenic Hemorrhage Control

Splenic hemorrhage should be controlled as any for other parenchymal organ bleeding. Initially pressure and packing should be used. If necessary the splenic pedicle can be occluded using gauze wrapped around the pedicle, a Rumel tourniquet, vascular clamps or Forrester sponge forceps with gauze between the jaws. Lacerations can be sutured and hemostatic agents can be used to control oozing. Stick ties are often all that is required with mid body or small lacerations. The omentum will help with hemostasis when incorporated in the suture. Synthetic mesh can also be used. Total splenectomy should be avoided unless essential. If the spleen is severely damaged it should be exteriorized without applying direct tension and removed. Ligation of splenic vessels can be performed with hand ties of 0 to 3-0 silk or with hemostatic clips. Ligation of the omental pedicle will also be necessary if there is any indication of a consumptive coagulopathy. Care must be taken to maintain pancreatic blood supply.

Times for Occlusion of Blood Vessels

In order to control hemorrhage temporary vascular occlusion of major blood vessels may be required. This helps prevent additional blood loss while also allowing the source of the bleeding to be identified and definitively controlled.

The descending thoracic aorta can be occluded for 5 to 10 minutes. With hypothermia and the addition of corticosteroids up to 30 to 40 minutes of occlusion time has been reported. The primary complication with prolonged occlusion times is paralysis. The abdominal aorta can be occluded for 30 to 40 minutes with increased time reported again if the patient is hypothermic and corticosteroids have been administered.

The following vessels can be occluded for up to 30 minutes: portal triad (hepatic artery, portal vein and common bile duct), hepatic artery alone, splenic artery and vein, renal artery and vein, abdominal aorta, distal caudal vena cava, iliac vessels, and femoral vessels.

Vessels Which Can Be Ligated

On occasion vessels may be traumatized to the point they are not salvageable. Alternatively hemorrhage into a tissue region may be uncontrollable unless the major vessel supplying the region can be ligated.

The following vessels can be ligated safely in most animals due to the presence of collateral circulation. Obviously anatomic variations may exist that could lead to serious consequences if these vessels are ligated and ligation should not be performed if a viable alternative exists.

Both femoral arteries
Both external iliac arteries
Both common iliac veins
Both femoral veins
Both femoral veins
Abdominal aorta below kidney
Abdominal vena cava below liver

Damage Control

Current human recommendations in cases of severe trauma requiring surgery to control hemorrhage are to keep the operative time to one hour or less. Prolonged operative time leads to hypothermia, worsening acidosis (related to decreased tissue perfusion and tissue hypoxia), and worsening of the coagulation status (primarily related to dilutional coagulopathy and loss of coagulation factors from ongoing hemorrhage). This is known as the 'trauma triad of death" - hypothermia, acidosis, coagulopathy. These factors all contribute to a worsening of the coagulation status of the patient and increased morbidity and mortality. The goal of "damage control" is to control major hemorrhage, provide rapid resection of damaged bowel to prevent ongoing leakage of bowel contents into the abdominal cavity, pack the abdomen, and get the patient out of surgery within one hour. The patient then is rewarmed, the acidosis is treated, and the coagulation status is normalized. Once the patient is more stable, the abdomen is reexplored (usually within 24-48 hours). Packing is provided with towels placed so as to provide direct pressure to oozing wounds. If packing is placed in the abdomen the abdomen may not be able to be closed primarily without causing excessive intraabdominal pressure. This increase in intraabdominal pressure can lead to abdominal compartment syndrome which can lead to decreased organ perfusion and secondary renal and gut failure. To avoid excessive pressure during closure of the linea a sterile sheet of plastic (large intravenous fluid bag cut open into a sheet) may need to be sutured to the linea alba edges. This way a waterproof dressing is in place preventing loss of warmth and protein, but abdominal compartment syndrome is avoided.

Summary

Every trauma patient should be assumed to have serious internal hemorrhage until proven otherwise. While aggressive fluid resuscitation is indicated in most cases the use of hypotensive resuscitation and external counterpressure may be successful in helping to manage serious intraabdominal hemorrhage until the bleeding can be definitively controlled. On occasion if the resources do not exist to take the patient to surgery this combination may give the patient enough time to clot and thus avoid the need to go to surgery. If diagnostic tests confirm the need for surgery a team of at least 3 individuals must be able to be called into action. These patients are critical and standard anesthetic protocols cannot be used. Positive pressure ventilation is essential. Blood products are often vital to the short and long term successful outcome of surgery for serious intraabdominal hemorrhage. The surgeon must have a thorough knowledge of anatomy since trauma can take you anywhere.

Introduction

Surgery is a fundamental part of emergency medicine. While some surgical diseases or injuries require advanced training and some patients may not be compromised by waiting until the arrival of a board certified surgeon (i.e., hemilaminectomy for a herniated disc or fracture repair) many patients presenting on emergency require emergency surgery. The emergency clinician must have the knowledge to be able to assess the patient to determine how urgently surgery is needed, the skills to deal with common emergency surgeries, and the equipment necessary to perform the surgery. The emergency clinician should be prepared to perform surgical cutdowns for airway and vascular access, control hemostasis accurately, and to debride and suture wounds. He or she must be capable of performing competently other lifesaving surgery such as an emergency thoracotomy to control hemorrhage or to perform open chest cardiac massage. Emergency celiotomy may be required to control hemorrhage from trauma (necessitating liver, splenic, renal, retroperitoneal or surgery of major blood vessels [i.e. aorta, vena cava]), gastric derotation and gastropexy for correction of gastric volvulus, gastrotomy or enterostomy for removal of foreign bodies, gastric or intestinal resections, pancreatic resection for necrotizing pancreatitis, cystotomy and urinary bladder repair, Cesarean section, ovariohysterectomy for pyometra, and placement of peritoneal dialysis catheters. The surgeon must know the indications for and be capable of performing open versus closed suction drainage of abdominal conditions or wounds. Many seriously ill or injured patients will require enteral nutritional support and the clinician should be competent at placing esophagostomy, gastrostomy, and enterostomy feeding tubes. The hospital must be equipped with the necessary supplies and instrumentation to perform these surgeries.

Lighting

Good overhead lighting that is high intensity, cool and can be directed is essential for doing emergency surgery. Emergency surgical procedures also may be required in the triage or treatment area such as a venous cutdown and slash tracheostomy. This ready area requires good lighting, similar to that required in the operating room. Dual lights that can be directed at divergent angles are especially important. A focusing high-intensity cool beam light and a wider beam reflecting dish light for general full-body illumination are recommended. A surgical headlight is key to good visualization while performing surgery especially when working in deep cavities.

Surgical Prep Solutions

The primary surgical prep solutions contain chlorhexidine, povidone-iodine or Techni-CareÒ (Care-TechÒ Laboratories, St. Louis, MO). All are broad spectrum. Chlorhexidine has a rapid kill (90% within 30 seconds) and because it binds to keratin it has residual effect. It is not inactivated by the presence of organic material as povidone-iodine is. The major problem in critical care units is that Pseudomonas can develop resistance to chlorhexidine. It is toxic to certain tissues and should not be used in and around eyes or ears. Povidone-iodine is available in scrubs and solutions. Scrubs contain detergents and should never come in contact with eyes, subcutaneous tissues, etc. It is inactivated by organic material, including blood, and it requires prolonged contact (90% within 2 minutes) for effective kill. Alcohol wipes should not be used in between application of povidone-iodine as it may reduce its effectiveness. It has been recommended that a scrub time of up to 5 to 7 minutes is required for both chlorhexidine and povidone-iodine to be effective. Techni-CareÒ is a surgical scrub (containing chloroxylenol and cocamidopropyl PG-dimonium chloride phosphate) that is reported to have a rapid kill (99.9% in 30 seconds). It is safe to use in wounds and on oral and ocular tissues. It contains substances that may actually aid in wound healing. It is a waterless scrub that may significantly reduce the hypothermia that can develop secondary to evaporative heat loss after using wet scrubs.

Sterilization

Critically ill and injured patients have depressed immune function making them more susceptible to infection and wound healing complications. Ideally all instruments being used during surgery should be autoclaved or gas sterilized. Cold sterile instruments should to be considered sterile and should be used with that fact in mind. Similarly suture material in cassettes should not be considered sterile once the cassette has been opened.

Instruments

All surgical packs will require a scalpel handle, scissors, hemostatic forceps, and needle drivers. The number and type of instruments will vary depending on the use for which the pack was intended. Minor laceration packs may only need a few instruments that are not necessarily of high quality. A major trauma surgical pack should have good quality instruments. A hemostat that falls off a blood vessel at an inopportune moment may contribute to significant patient morbidity. Scissors should be sharp and should be checked regularly to ensure that sharpening or replacement is not indicated. Needle drivers with replaceable tungsten carbide tips are preferred. Once the tips are worn and will not hold the finer suture the tips can be replaced. Olsen-Hegar needle drivers are not recommended since inadvertent cutting of suture material, especially during continuous suture patterns, can contribute to frustration and morbidity. Curved instruments are preferred over straight because they allow for better visualization of tissues to be cut and are more maneuverable. A variety of retractors are available. Handheld retractors include Senn, Army-Navy, and malleable retractors. Self-retaining retractors include Balfour retractors that are typically used in the abdomen but can be used for the chest, Finochietto rib retractors, and Gelpi and Weitlaner retractors.

Staplers

Stapling equipment is invaluable in saving time and preventing patient morbidity - as long as the equipment is used appropriately. Stapling equipment can be used to perform rapid lung lobectomy, liver lobectomy, gastric resection, intestinal anastomosis (GIAÒ, United States Surgical Corp., Norwalk, CT), vascular ligation (LDSÒ, United States Surgical Corp., Norwalk, CT) and skin and fascia closure. The most commonly used internal stapler is the TAÒ (thoracoabdominal) stapler (United States Surgical Corp., Norwalk, CT). The 4.8 mm staples cannot be used on tissue that will not compress to less than 2 mm in thickness and the 3.5 staples should not be used on tissue that does not compress to less than 1.5 mm in thickness. These provide two staggered rows of stainless steel staples that form a B shape when they compress. The length of the suture line is variable from 30 mm to 90 mm in length. This shape provides hemostasis without compromising tissue healing. Staples lines may need to be oversewn. HemoclipsÒ (Solvay Animal Health Inc., Mendota Heights, MT) and LigaclipsÒ (Ethicon Inc., Somerville, NJ) also are used routinely for vascular ligation. Vessels should be between one-third and two-thirds the diameter of the clip when it is applied and should not be greater than 11 mm in diameter. A tissue bumper of 2 to 3 mm should be left to avoid the clip slipping off. Skin staplers (ReflexÒ One, ConMed Corporation, Utica, NY) can save significant time when closing incisions.

Scalpel Blades

Typically 3 scalpel blades are used. Number 10 blades are used for cutting skin linea alba and cutting tissues where finesse is less important. Number 11 blades are typically used for making stab incisions. Number 15 blades are used where finesse is more important. Due to the rounded tip penetrating too deeply is less likely than if a number 11 blade is used.

Suture Material

Both monofilament absorbable and nonabsorbable suture material on taper and cutting needles size 2 to 5-0 and silk (sizes 0 and 2-0) is advised. Braided material can form a nidus for infection and is generally avoided if infection is suspected or documented. The smallest suture material that can hold the tissues together should be used. Large material may interfere with blood supply by crushing the tissue and may interfere with wound healing. Taper needles generally are preferred over cutting needles except when suturing skin since they tend not to tear tissue. In addition taper needles tend to push small vessels out of the way rather than puncturing them thus minimizing hemorrhage. For tubes that need to be anchored to periosteum (chest drains, esophagostomy tubes) a taper needle is essential because a cutting needle will tear the periosteum whereas a taper needle will not.

Gut is very reactive and loses 33% of its tensile strength in 7 days. This makes it unsuitable for many emergency surgeries. It is generally absorbed totally within 60 days. Polyglactin 910 (Vicryl, Ethicon) is minimally reactive but is multifilament and is not recommended if infection is present. Like gut it is totally absorbed within 60 days. Polydioxanone (PDS II, Ethicon) has good security and minimally reactive. Its monofilament nature and maintenance of tensile strength (14% loss in 14 days, absorbed in 170 days) make it suitable for many emergency surgical conditions. Polyglyconate (Maxon, Davis & Geck) has similar knot security and reactivity as Polydioxanone. It loses approximately 30% of its tensile strength at 14 days and 45% at 21 days. Silk is very reactive and being braided should not be used in the presence of infection. However its handling capabilities make it very useful for vascular ligation.

Nonabsorbable monofilament sutures included polyamide materials (nylon), polypropylene (Prolene-Ethicon, Surgilene-Davis & Geck, Fluorofil-Mallinckrodt Veterinary), and polybutester (Novafil-Davis & Geck). Polypropylene has excellent knot security and is preferred for all internal suturing. Polybutester has slightly less knot security than polypropylene but more than nylon. Polymerized caprolactum (Braunamid-Braun, Supramid-Jackson), which also is a monofilament nonabsorbable suture, is not recommended due to the high likelihood of tissue reaction (including development of fistulous tracts) if the coating breaks. In addition it is usually distributed in cassette that cannot be considered sterile once opened.

Generally skin is sutured with a monofilament nonabsorbable suture. If monofilament absorbable suture is used to suture skin it should be removed since absorbable sutures require contact with body fluids to dissolve. Absorbable suture is used for subcutaneous tissue. The rectus abdominis sheath should be closed with monofilament material. Nonabsorbable suture is recommended if there are any concerns for wound healing. Muscle has poor holding power. The fascia can be closed using absorbable or nonabsorbable suture. Tendon should be sutured using monofilament nonabsorbable suture. Parenchymal organs should be sutured with absorbable monofilament suture and hollow organs can be sutured with absorbable monofilament or braided materials (unless infection is present. Suture material should be minimized in infected or contaminated wounds (gross spillage from the gastrointestinal tract, entry into the genitourinary or biliary system in presence of infection or fresh traumatic wounds).

Hemostasis

Hemostasis generally is achieved by direct pressure, suturing of wounds (compression of vessels), electrosurgery, ligation of vessels, vascular clips, omental packing, use of superglue, use of hemostatic agents or removal of the organ that may be bleeding. There are numerous products available in veterinary and human medicine for hemostasis many of which are based on gelatin, fibrin, bovine thrombin, seaweed and a variety of other natural products that have hemostatic qualities.

Electrosurgery is indispensable for rapid and efficient control of hemorrhage in critically ill or injured patients who are predisposed to being anemic and have coagulopathies. It causes heat-induced protein denaturation and tissue coagulation and can be used to control hemorrhage from arteries up to 1 mm and veins up to 2 mm in diameter. Monopolar electrosurgery passes a current between the electrode through the patient to a ground plate. It requires a dry field as opposed to bipolar electrosurgery where the current passes between 2 electrodes. Thermal damage is a potential side effect of monopolar electrosurgery and to a lesser extent with bipolar electrosurgery that can lead to ischemia and delayed healing.

Wound irrigation

Wound and body cavity irrigation forms an important part of any surgical procedures. "Dilution is the solution to pollution." Sterile isotonic solutions such as 0.9% saline, lactated Ringer's solution, Plasmalyte 148/Plasmalyte-A or Normosol-R are preferred for irrigation. Antibiotics should not be added to irrigation fluids and extreme care should be exercised when adding disinfectants to irrigation fluids. Body cavities should be irrigated with sterile isotonic fluid only. Wound irrigation can be performed using sterile isotonic fluids (preferred) or occasionally with solutions that contain disinfectants as they can be toxic to cells. Chlorhexidine should be used at higher than 0.05% concentration. Povidone-Iodine should not be used at higher than 1% solution. The low pH of this solution may worsen a local acidosis. Dakin's solution (0.05% sodium hypochlorite, 1:1- laundry bleach) kills bacteria effectively and liquefies necrotic tissue but can be detrimental to neutrophils, fibroblasts, and endothelial cells. Tap water can cause cell damage due to its hypotonic nature but differences in outcome from wounds lavaged in tap water versus isotonic solutions have not been noted.

Irrigation can be provided using mechanical lavage systems designed for wound irrigation or using a 35 ml syringe and an 18- to 19-gauge needle. Pressure generated by the irrigator should not exceed 7-9 PSI.

Drains

Drains are classified as either active or passive. An active drain has a suction system attached whereas a passive drain dos not. Drains are indicated to help eliminate dead space and fluid accumulation and to help prevent fluid and/or air accumulation. Active drains are preferred over passive drains (penrose) because they decrease the likelihood of infection, keep the skin dry, provide effective continuous drainage, and allow monitoring of effluent.

Instrument packs

The number and type of surgical packs will vary with the practice; however, at a bare minimum wound packs, a major trauma pack, and a vascular pack should be available. The major trauma pack can be used for any other major abdominal or thoracic surgery in combination with individually sterilized instruments and the vascular pack. The surgical instruments should be packed with the emergency surgery in mind and the instruments that the surgeon may require first should be placed on top. A separate peel pack (not sealed) should contain the necessary instruments for gaining rapid entry to an abdomen to thorax as well as rapid hemostasis control.

Wound Pack
Scalpel handle
Mayo-Hegar needle holder
Brown-Adson tissue forceps
Curved Metzenbaum scissors
Curved Halstead mosquito forceps (minimum 3)
Curved Kelly or Crile forceps (minimum 3)
Small bowl
4x4 sponges (minimum 10)
Skin drape

Trauma Pack*
Saline bowls (small and large)
2 scalpel handles (#3)
Backhaus towel clamps - small (minimum 8)
Backhaus towel clamps - large (minimum 4)
Curved Mayo scissors (small and large)
Curved Metzenbaum scissors (small and large)
Curved Halstead mosquito forceps (minimum 6
Curved Kelly or Crile forceps (minimum 6)
Curved Rochester-Carmalt hemostatic forceps (minimum 4)
Curved Forrester sponge forceps
Allis tissue forceps (minimum 4)
Right angle forceps (small and large)
DeBakey tissue forceps (fine-tipped)
Russian thumb forceps
Brown-Adson tissue forceps
Mayo-Hegar needle holders - small and large
Poole suction tip
Yankauer suction tip
Silastic tubing for suction
5 Fr red rubber tubing
Bulb syringe
Laparotomy pads (5)
Cotton towels 4 small
Gauze sponges 4x4 (20)
Skin drapes

Vascular Pack*
Jeweler's forceps
Ryder micro needle holder
DeBakey forceps - micro-tipped
Curved black handle Metzenbaum scissors tenotomy tips
Angled air injection cannula (27 ga)
Magnifying loupes
Curved eye dressing forceps
Serrefine forceps (bulldog clamps) (2)
Finochietto rib retractor (optional)
Cooley vascular forceps (2)
Right angle forceps -fine-tipped, small and large (2 of each)
Micro Satinsky vena cava clamp (2)
Curved extra delicate mosquito forceps (4)

Individual Packs
A minimum of 2 to 4 separate packs of instruments should be available for minor surgeries as well as major surgery where the number or instruments in the pack is insufficient. A minimum of 6 packs of twenty 4x4 gauze sponges should be available as well as a minimum of 2 packs of 5 laparotomy sponges. The following are only guidelines and should be modified according to the individual practice.

Towel clamps (packs of 2-4)
Curved Halstead mosquito forceps (2 minimum) (packs of 1-3)
Curved Kelly hemostatic clamps (2 minimum) (packs of 1-3)
Doyen intestinal forceps (2)
Frazier suction tip
Senn retractors (2) (individually wrapped)
Army-Navy retractors (2) (individually wrapped)
Gelpi retractors (small, large, deep angle large) (2 of each)
4 x 4 gauze sponges (6 minimum) (packs of 20)
Laparotomy sponges (2 minimum) (packs of 4-5)
Sterile towels (2 minimum) (packs of 2-4)
Finochietto rib retractor (medium) (optional)
Balfour retractor - small and large

*Based on recommendations by Dr. D. Tim Crowe, Jr., DACVS, DACVECC

References available upon request.