December 2006
Critical Care
Karol A. Mathews, DVM, DVSc, DACVECC
Ontario Veterinary College
University of Guelph
Guelph, Ontario, Canada
Acute Pain Management for Cats
INTRODUCTION
Pain is present in all surgical, traumatic and many medical conditions. The demonstration of pain is not always obvious, therefore an animal should be assumed to be experiencing pain in any condition expected to produce pain in humans. Response to analgesic administration (as with any other therapy-directed treatment of a problem) can guide the veterinarian in the management of pain (or presumed pain). Return of normal behaviour, including eating, sleeping in the curled up position, 'normal stretching', grooming and a general appearance of well-being, is the goal to achieve. This practice will allow the practitioner to gain experience in recognizing and treating pain in cats. Administration of opioid analgesics is frequently withheld in ill or injured animals as it is the belief that these drugs will "mask" the signs of deterioration. This is not so. In fact, the opposite occurs where alleviating pain and reducing the associated response of the sympathetic nervous system to pain, will allow the practitioner to focus on other causes of tachycardia, tachypnea, pale mucous membranes and weak pulses. If hypovolemia or hypotension re not present, these parameters frequently return to normal after administration of analgesics.
IN GENERAL, Cats typically remain quiet and motionless, but occasionally may growl, when in mild to moderate pain and may thrash, growl and scream when pain is severe. Cats may still purr when painful to any degree and, in fact, up until death. The term 'depressed' in this text means slow or a 'hang-dog' response to a situation where the cat would normally act as described in pain level 0. They may appear 'tired', the palpebral fissures may be incompletely open, with a low carriage of the head. Alternatively, the cat may remain in sternal with eyes closed, or partially open, not moving for several hours. The level of depression may vary from that just described to poorly or non-responsive to caregiver.
Painful sensations such as dull aching, sharp shooting, throbbing, stinging - we have all experienced these at some time - can be experienced in any individual as a single or multiple experience. A single patient can experience a combination of these painful sensations after trauma, after major orthopedic surgery, or medical pain combined with a surgical procedure (laparotomy). Combinations of different classes of analgesics are recommended in these animals, as one analgesic class alone is usually not adequate to control all types of pain.
NOTE: Where NSAIAs are recommended it is assumed that there is no contraindications for their use.
TABLE 1: Suggested Analgesics for the Initial Management of Acute Pain in Cats
Severe to excruciating pain:
Titrate opioid to effect: the author's preference is fentanyl 3-5mcg/kg increments (usually 10-20mcg/kg with potentially requiring up to 50mcg/kg for anesthesia, intubation + ventilation); 0.1- 0.2 mg/kg oxymorphone or hydromorphone; or methadone 0.2-0.5mg/kg; the effects of a similar dose of morphine may require up to 4 hours for full affect. Using the effective dose divided by 2-4 to establish an hourly SC or IV constant rate infusion (CRI). The initial effective dose of fentanyl should be given as an hourly CRI. In a cat with normal renal function, ketamine 1-4 mg/kg IV as a bolus, combined with the opioid above, and continued as a CRI titrating this range/h, is advised to reduce the opiate requirement. In the fractious cat. (Ketamine 2-10mg/kg into the mouth may be used to facilitate restraint). Consider using local anesthesia or epidural anesthesia where possible. It may be necessary to anesthetize the patient while attempting to find or treat the inciting cause. Remove the inciting cause immediately. This degree of pain can cause death.
| | Drug
| Dose
| Duration of Action or Dosing Interval
| | Moderate to severe pain:
| Fentanyl
Use low end of the dose for moderate pain
| 1 - 10+ mcg/kg
3-6 mcg/kg CRI
| 0.3 h
1 h
| Hydromorphone
Use low end of the dose for moderate pain
| 0.02 - 0.1+ mg/kg IV, IM, SC
| 2-6 h
| Morphine or Methadone.
Use low end of the dose for moderate pain
| 0.1 - 0.2+ mg/kg IM, SC
For IV dosing use half the low end dose, titrate over 3-5 minutes
| 2-6 h IM, SC
1-4 h IV
| #Ketamine
Use low end of the dose for moderate pain
| 1-4 mg/kg IV
2-10 mg/kg PO
0.2-4mg/kg CRI
| Prn (~0.5 h)
1 h
| |
NOTE: Opioids should be given to effect even beyond dosing and frequency noted if necessary
| | Mild to Moderate pain:
| *Opioids listed above for moderate pain
Butorphanol
Use low end of dose for mild pain
| Low end of dosage range
0.1- 0.4 IV,
0.4-0.8 mg/kg IM, SC
|
0.5-1 h
| | Meperidine (pethidine)
| 5-10 mg/kg IM, SC
| 20-30min
|
Used with permission PAIN HURTS CD. KAMathews ed.. Guelph, Ontario Canada. Jonkar Computer Systems 2003
TABLE 2: Suggested Analgesia for Various Levels of Ongoing Pain
Severe to excruciating pain:
Requires multimodal analgesia titrated to effect. Opioids: you must give at least 0.2 mg/kg oxymorphone or hydromorphone (suggest titrating up to this dose IV to effect over 3-5 minutes); OR fentanyl (the author's preference for cats), 10 to 20mcg/kg slow titration with up to 50 mcg/kg/h CRI if a level approaching anesthesia is required (intubation + assisted ventilation); + NSAIAs where not contraindicated. Ketamine 1- 4 mg/kg combined with the opioid above as a bolus and followed with a 1-4mg/kgh CRI is advised to lower the opiate requirements. Each class of analgesic should be titrated to effect. Tachycardia may persist. It may be impossible to control the pain. Consider combining the above analgesics with epidurally placed analgesics or local neural blockade, or anesthetize the patient while attempting to find or treat the inciting cause. Remove the inciting cause immediately. This degree of pain can cause death.
NOTE: Opioids and ketamine as a CRI can be combined in IV crystalloid fluids (lactated Ringer's or Ringer's may not be compatible due to calcium content). It is recommended to place the medication in a burette in-line with the maintenance fluid rate. Additional individual drug can be placed in the burette, or additional fluids can be added to dilute if reduction is required.
| | Drug
| Dose
| Duration of Action or Dosing Interval
| | Moderate to severe pain:
| Morphine or Methadone
Although morhpine has been recommended for cats, the onset of action is quite slow and may not be suitable to manage pain acutely. Suggest fentanyl, oxymorphone or hydromorphone
| 0.1-0.5+mg/kg IM, SC or titrate to effect over 3-5 minutes if given IV. Addition of a sedative may be required.
Administer intermittently or follow with a CRI with effective dose over dosing interval
| 2-4 h
| | Oxymorphone or Hydromorphone
| 0.05 - 0.1+ mg/kg IV, IM, SC
Administer intermittently, or follow with a CRI of the effective dose obtained with slow push over the 2-4h dosing interval
| 2-4h
| | Fentany l (author's preference)
| 4-10+ mcg/kg IV bolus
4-10+ mcg/kg/h
| 0.3 h
CRI
| | Fentanyl patch
| 12.5 mcg/h
| 6-12h for effect and may last up to 5 days
| #Ketamine combined
with an opioid or sedative
| 0.5-2+ mg/kg/h IV, SC
0.2-2+mg/kg IV
| Bolus
CRI
| Ketoprofen*
Do not use if hemorrhage is a concern
| 2 mg/kg SC
Then < 1 mg/kg
| Once, then
every 24h up to 4 days
| | Meloxicam*
| < 0.2 mg/kg SC, PO LEAN WEIGHT
then < 0.1 mg/kg
then 0.05mg/kg
| Once, then
every 24h up to 3 days
every second day
| | Carprofen*
| 2 mg/kg SC LEAN WEIGHT
| Once only
| | Flunixin meglumine*
| 1 mg/kg SC LEAN WEIGHT
| Once only
| Ketorolac tromethamine*
Do not use if hemorrhage is a concern
| 0.25 mg/kg IM LEAN WEIGHT
| Repeat once in 8-12h
| | Bupivacaine 0.5%
| Intra-pleural and peritoneal use: Mix 1mL bupivicaine with 0.1mL sodium bicarbonate and administer at 1 mg/kg (0.2 ml/kg lean weight) diluted to 6 mL with saline. Flush this through tube with volume of 0.9% saline equal to volume of chest drain.
| 6 h
| | Mild to moderate pain:
| | Opioids above
| Low dosages
| Titrate down to lowest effective dose
| | Buprenorphine
| 0.005-0.01 mg/kg IV, IM
0.01-0.002 mg/kg sublingual
| 4-8h
7h
| | NSAIAs above
| Low dosages
| Titrate down to lowest effective dose
| | Butorphanol
| 0.1 - 0.4 mg/kg IV, IM, SC
Administer intermittently or follow with a CRI with effective dose over dosing interval
| 2 h
| | Meperidine (pethidine)
| 5 - 10 mg/kg IM, SC for short duration analgesia or administered at time of NSAIA injection.
| 20 - 30 minutes
| | Morphine syrup
| 0.5 mg/kg PO- titrate to effect
| Every 4-6 h
| | Codeine
| 0.5-2 mg/kg PO- titrate to effect
| Every 6-12 h
| | Bupivacaine 0.5%
| As above
| 6 h
| | Sedatives to combine with opioids:
| | Midazolam
| 0.1 - 0.5 mg/kg IV, IM
| Can be >6h
| | Diazepam
| 0.1 - 0.5 mg/kg IV
| Can be >6h
| | Acepromazine
| 0.01 - 0.05 mg/kg IV
0.02 - 0.1 mg/kg IM, SC
| 1-2 h
2-6 h
| | @Medetomidine
| 0.002 -0.004 mg/kg IM, SC
|
|
*Review contraindications for NSAIA administration for safety information. It is not always necessary to administer the recommended loading dose. It is advised that a dose as low as possible is used to manage the varying degrees of pain. This will reduce the potential for adverse effects.
# Not first line but may be beneficial in difficult to manage cases.
@Medetomidine has both analgesic and sedative effects. Only use in otherwise healthy cats. If used prior to induction of general anesthesia, titrate induction agent with one-quarter increments of usual dose.
NOTE: The drugs and doses given are suggestions. If the pain is not being managed, then increase to effect (not NSAIAs). If administered IV, morphine must be administered slowly to prevent hypotension in all animals. Ketamine 1-4+ mg/kg IV or 10 mg/kg per os (fractious with no IV access), may be an alternative to control pain quickly if opioids are not available and renal function or hypertrophic cardiomyopathy is not a concern. Buprenorphine can be administered in a similar manner. For severe to excruciating pain, in cats with normal renal function, and after appropriate dosing with an opioid agonist, ketamine (100 mg/l) and diazepam (5 mg/ml) or midazolam (5 mg/ml) mixed 1:1 and administered at 0.05 - 0.15 mL/kg, to effect should also be considered as general anesthesia may be required.
As pain sensation is an individual experience, one animal appearing more painful than another with a similar condition, an individual approach to pain management is required. While suggestions for treatment can be made for mild, moderate and severe pain, response to analgesic therapy is the best approach. If the animal is still considered painful, increase the dose or add another class of analgesic. Assigning the severity of trauma or degree of surgical invasiveness and tissue manipulation to a case may guide you as to which analgesic and how much to give, but even this has its variability. Surgical 'trauma' (tissue handling) and duration of the surgical procedure will influence the degree of post-operative pain. The combination of NSAIAs and opioids confers excellent analgesia for moderate to severe orthopedic procedures and certain soft tissue injury (including surgical) where inflammation is a feature.
TABLE 3: Suggested Analgesic Regimens Associated with Behaviour
| Pain Value
| Pain Description
| | 0
| No pain. Patient is playing, jumping, sitting or walking normally. Sleeping comfortably curled up. Normal, affectionate response to caregiver; will rub their face on the caregiver's hand or cage, may roll over and purr. Heart rate should be normal, but if elevated, it is due to excitement. Cats will groom themselves when free of pain. Appetite is normal. Behaviour different from this, not associated with pain, may be associated with a medical illness, apprehension or anxiety. Apprehension/anxiety can be a feature of hospitalized patients.
| | 1
| Probably no pain. Patient appears to be normal but condition is not as clear-cut as above. Heart rate should be normal, or slightly increased due to excitement. Cats may still purr.
| | 2
| Mild discomfort. Patient will still eat or sleep but may not curl up. May limp slightly or resist palpation of the surgical wound, but otherwise shows no other signs of discomfort. Not depressed. There may be a slight increase in respiratory rate; heart rate may or may not be increased and may still purr. Reassess within the hour; give an analgesic if condition appears worse.
| | 3
| Mild pain or discomfort. Patient will limp or guard incision or the abdomen may be slightly tucked up if abdominal surgery was performed. Looks a little depressed. Cannot get comfortable. May tremble or shake. Appears to be interested in food when offered and may still eat a little but somewhat picky. This could be a transition from 2 above, so you notice a change from being comfortable to becoming restless, as though the analgesia is wearing off. Respiratory rate may be increased and a little shallow. Heart rate may be increased or normal, depending on whether an opioid was given previously. The cat may continue to purr even when in pain, therefore disregard this as an indicator of comfort. Needs analgesia. The analgesic selected will depend on whether ( i) it is a repeat in a patient with moderate to severe pain (fracture repair), or (ii) the patient has a problem resulting in mild to moderate pain.
Analgesia:
If (i), then continue with fentanyl 2-5+mcg/kg/h, morphine IM, SC 0.2-0.3+ mg/kg or oxymorphone or hydromorphone 0.05 mg/kg IV,IM, or methadone at 0.2-0.5 mg/kg IV,IM,SC or an injectable NSAIA, if not contraindicated).
If (ii), then administer butorphanol 0.2 - 0.4 mg/kg, or buprenorphine 0.005 mg/kg, or NSAIA where appropriate. If this is a mild pain situation, fentanyl, oxymorphone, hydromorphone or morphine is not necessary as the patient may become dysphoric.
| | 4
| Mild to moderate pain with the patient resisting touching of the operative site, injured area, painful abdomen, etc. Guarding or splinting of the abdomen. The patient may sit crouched (especially medical pain or abdominal/thoracic surgery) or lie in an abnormal position (relative to injury) and is not curled up or relaxed. May or may not appear interested in food. May start to eat and then stop after 1 or 2 bites. Respiratory rate may be increased or shallow. Heart rate may be increased or normal. Pupils may be dilated. May cry occasionally, be slow to rise and, hang the tail down. There may be no weight bearing or a toe touch on the operated limb. Will be somewhat depressed with reduced response to caregiver. Often, cats may lie quietly and not move for prolonged periods.
Analgesia. As for 3 above but at high end of the range dosages. If patient has already received an opioid, consider a NSAIA as an adjunct to opioid.
| | 5
| Moderate pain. As above but condition progressing from above. Patient may be reluctant to move, usually remaining in a crouched position, depressed, inappetant and may bite or attempt to bite when the caregiver approaches the painful area. The patient may vocalize when caregiver attempts to move them or when it is approached. There is definite splinting of the abdomen if affected (ie peritonitis, pancreatitis, hepatitis, incision), or the patient is unable to bear weight on an injured or operative limb. The ears may be pulled back. The heart and respiratory rates may be increased. Pupils may be dilated. The patient is not interested in food, will lie down but does not really sleep. Frequently, cats may lie quietly and not move.
Analgesia. Buprenorphine 0.01 mg/kg, or fentanyl 2-3 mcg/kg followed with CRI, oxymorphone or hydromorphone at 0.05 - 0.1 mg/kg, or +morphine 0.2-0.5 mg/kg, or methadone 0.2-0.5 mg/kg q 3-6h, for soft tissue or orthopedic problems. Consider an injectable NSAIA, either alone or as adjunct to opioids, if orthopedic and soft tissue surgery or injury, where there are no contraindications. Lower dosages of opiate are required when combined with a NSAIA.
| | 6
| Increased moderate pain. As above (5), but patient may vocalize without provocation and when attempting to move. Heart rate may be increased or within normal limits if an opioid was administered previously. Respiratory rate may be increased with an abdominal lift. Pupils may be dilated.
Analgesia. Fentanyl 3 - 5 mcg/kg bolus followed as a CRI, or oxymorphone or hydromorphone 0.1 - 0.2 mg/kg, or methadone or+ morphine 0.3-0.5 mg/kg IM, SC or slow push IV q3-6h continued at the same dose as a CRI. Administer an injectable NSAIA, especially if the pain is associated with an orthopedic problem and there are no contraindications. A lower dosage of opiate is required with co-administration of an NSAIA.
| | 7
| Moderate to severe pain (include signs from 5 & 6 above). The patient is very depressed and is not concerned with its surroundings but usually responds to direct voice (this may be turning of the head or eyes). The patient will urinate and defecate (if diarrhea) without attempting to move, will cry out when moved or spontaneously. Occasionally an animal doesn't vocalize. Heart and respiratory rates may be increased. Hypertension may also be present. Pupils may be dilated.
Analgesia: Patients require a higher dose of +morphine, fentanyl, oxymorphone, hydromorphone, or methadone; give any of these opioids to effect. Combine with a NSAIA , especially if orthopedic pain. Addition of ketamine bolus 1-2mg/kg and CRI of 0.25-2 mg/kg/h should be considered in addition to the opioid and NSAIA (where appropriate) if pain is not controlled. Epidural and/or Local analgesia/anesthesia should be considered where indicated.
| | 8
| Severe pain. Signs as above (7). Vocalizing may be more of a feature, or so consumed with pain the patient will not notice your presence and just lie there. The patient may thrash around in the cage intermittently. If it is traumatic or neurological pain, the patient may scream when being approached. Tachycardia, + tachypnea with increased abdominal effort and hypertension are usually present even if an opioid was previously given, although these can be unreliable parameters if not present.
Analgesia: High dose oxymorphone, hydromorphone or +morphine IM, SC or CRI, to effect, or fentanyl (induce with 5-10 mcg/kg and maintain as a CRI. Add an injectable NSAIA especially if orthopedic pain, with no contraindications, add ketamine 1-4 mg/kg bolus followed by 0.5-2mg/kg/h CRI Epidural and/or Local analgesia/anesthesia should be considered where indicated.
| | 9
| Severe to excruciating. As above (8), but patient is hyperesthetic. The patient will tremble involuntarily when any part of the body in close proximity to wound, injury, etc. is touched. Neuropathic pain (entrapped nerve or inflammation around the nerve) or extensive inflammation anywhere (ie peritonitis, pleuritis, fasciitis, myositis, especially when caused by a streptococcal organism; severe necrotizing pancreatitis).
Analgesia: Requires high dose oxymorphone, hydromorphone IM, SC or CRI given to effect or +morphine IM, SC or CRI; OR fentanyl (5-10mcg/kg may require up to 50 mcg/kg/h CRI - anesthesia with intubation); + NSAIAs where not contraindicated; or + 2 - 4 mg/kg ketamine IV bolus followed by 2-4mg/kg CRI. Tachycardia may persist and may be impossible to control the pain. Consider combining analgesics with epidurally placed analgesics or local blocks, or anesthetize the patient while attempting to find or treat the inciting cause. Remove the inciting cause immediately. This degree of pain can cause death.
| | 10
| As above (9), but patient emitting piercing screams or almost comatose. The patient is hyperesthetic/hyperalgesic, pain is elicited wherever you touch the patient
Analgesia: Very high doses of opioids do not relieve this pain; however, you must give at least 0.1 mg/kg oxymorphone or hydromorphone, or +morphine 0.5 mg/kg VERY slowly IV (give more if needed, to effect), or fentanyl (5 - 10 mcg/kg and maintain up to 50 mcg/kg/h anesthesia with intubation) and consider combining this with NSAIAs where not contraindicated, and/or 1-4 mg/kg ketamine bolus followed by 1-4mg/kg/h CRI. This combination of analgesics may result in anesthesia requiring intubation + assisted ventilation. It may be necessary to anesthetize the patient while attempting to find or treat the inciting cause. Epidural and/or Local analgesia/anesthesia should be considered where indicated. This degree of pain can cause death.
|
+NOTE: Morphine may have a very slow onset of analgesic action, therefore, fentanyl, oxymorphone or hydromorphone are preferred if available.
If the pain is not being managed, then increase analgesic to effect (opioids and ketamine), or add another class (NSAIA). In the author's experience, there have been minimal or no side effects with high dose opioids when animals are painful.
Neuropathic Pain may be associated with a variety of surgical procedures or medical conditions.
Gabapentin is a useful adjunctive analgesic for neuropathic pain. Pain associated with neuritis, nerve entrapment secondary to trauma, cervical or thoracolumbar disc disease or post-laminectomy can be responsive to gabapentin. Gabapentin can be used in combination with opioids. Post-seizure or CPR vocalization, if relentless, may also be managed with gabapentin.
Suggested range in cats is 2.5-5 mg/kg q12h, for pain. This author starts at 5 mg/kg and increase if no effect seen in 2 hours. There may be a higher requirement for post-seizure or post-CPR vocalization and thrashing. Wean off slowly otherwise the patient will experience worse pain. Reduce in renal insufficiency. Usually the limit of dosing is reached when the animal is sedated.
TABLE 4: Adjunctive Analgesics Suggested Dosages
| Drug
| Dosage (mg/kg)
| Route of Admin
| Duration
| | Ketamine
| 0.5-4 mg/kg/h
| IV
| bolus for control followed by CRI depending on severity of pain
| | Gabapentin
| 2.5-5 mg/kg (10 rarely)
| PO
| q12h
Wean off slowly
| | Amantadine
| 3mg/kg
| PO
| q24h
| | Amitriptyline
| 2.5-12.5 mg/cat
| PO
| q24h
| | Imipramine
| 2.5-5 mg/cat
| PO
| q12h
|
The tables and information contained in this manuscript are used with permission from Mathews KA Ed. PAIN How to Understand Recognize Treat and Stop CDs/DVD (www.jonkar.com), Jonkar Computer Systems, Guelph, Ontario, Canada.
Pain, Swelling ... and Nasty Wounds
Introduction
Dogs, and rarely cats, may present to the veterinarian because they 'aint doing right', associated with acute pain, with or without noticeable swelling or injury, of the affected area. It is important to consider bacterial fasciitis or myositis in these animals and to avoid administration of analgesics or antibiotics without pursuing the underlying cause. As a number of bacterial organisms may cause bacterial fasciitis, identifying the organism involved and prescribing the appropriate antibiotic is important. Progression of this disease is rapid and owners should be warned of the potential of this. The use of non-steroidal anti-inflammatory analgesics in humans with streptococcal fasciitis has also been linked to increased mortality; it is not clear if this is due to masking of clinical signs thereby facilitating the progression of disease without appropriate management, or whether there is a direct affect.
Toxic Shock Syndrome
Streptococcal infections may lead to streptococcal toxic shock syndrome (STSS) in people and animals. A part of this syndrome is necrotizing fasciitis (NF), a rapidly progressive and destructive infection of the subcutaneous and fascial tissue associated with high mortality if not recognized in the early stages of the disease. Streptococcal myositis involves muscle rather than fascial tissue, and is fatal. Group A streptococci (GAS) re-emerged in the 1980s as a more virulent pathogen in human patients, the so-called 'flesh-eating disease. Group A streptococcus has many M-type proteins which contribute to the varying degrees of virulence. The Group G streptococci (GGS), has been implicated in both human and animal infections. Strains of GGS can be differentiated and a subset of these bacteria has been identified as Streptococcus canis (SC). Streptococcus canis has been isolated from urinary tract infections, mastitis, vaginitis , metritis, mastitis, skin infections and sepsis in dogs but have not been reported to induce rapidly fatal toxic shock. However, STSS has emerged in dogs and to a lesser degree, in cats. The necrotizing fasciitis and myositis aspects of this disease appears sporadically therefore, the veterinarian must always be on the alert for animals potentially infected with the SC. While SC is the organism most often implicated, a similar presentation may occur with Pseudomonas aeruginosa, Escherichia coli and Clostridial spp infections. It is important therefore, to pursue culture and antibiotic sensitivity of the lesion.
Clinical Presentation and Diagnosis
Animals of all ages can acquire this illness. Most dogs with NF are reported to be healthy a day to hours prior to admission. Fever (40 - 41 C) with a history of acute to per-acute onset of major presenting signs should alert the practitioner. A consistent sign of NF is intense pain over an area of swelling at the time of presentation, or where swelling developed within 24-48 hours after admission. A key feature of this disease is intense to excruciating pain disproportionate to the initial purported injury, wound or unidentifiable lesion. SC infections associated with toxic shock syndrome may be present in any organ (ie lung, prostate, lymph node or nervous system). As examples, a dog presenting to the OVC with per-acute dyspnea had a history of chronic cough died within hours. Another dog with prostatitis with extension of SC infection to peripheral nerves was hyperalgesic with severe diffuse pain; this dog also died of septic shock within hours of presentation. Swelling of a submandibular lymph node in one dog progressed to pharyngeal and tracheal obstruction within 2 hours. Usually, with SC there is no discolouration or demarcation on the skin initially, however, this progresses to erythema. Pseudomonal fasciitis was diagnosed in a dog following subcutaneous administration of fluids; this dog had marked discolouration of the area with visible, rapid progression. .
Fine needle aspiration of the swollen area (attempt to identify a soft fluctuant area) should be performed. Grey/cream coloured, non-odiferous purulent material is identifed with SC; however, material aspirated from clostridial infections is odiferous. Stat cytological examination reveals cocci in chains with SC infections, rods with E.coli infections and larger, plump rods with clostridial infections.
Management
Emergent, aggressive debridement, extensive irrigation, and treatment with honey or sugar as described in references 3 and 4 below, with the entire site left open to drain into bandages, is recommended. Most of these animals require intensive supportive care including aggressive pain management (opiates, and ketamine by constant rate infusion), crystalloids and colloids; fresh frozen plasma, oxygen therapy, dopamine or dobutamine are also frequently required in the peri-operative period. As a broad recommendation, the antibiotic of choice is -lactam antibiotic (amoxicillin/clavulanate - Clavamox , Pfizer) if oral administration is possible, or clindamycin for SC, fluoroquinolone for E.coli and metronidazole for clostridial infection. However, a broad-spectrum antibiotic such as meropenem is advised in the critically ill patient prior to receiving bacterial identification and antibiotic susceptibility as this frequently takes 2-3 days. Changing to the most appropriate antibiotic is advised once these results have been received. Of major concern is administration of a fluoroquinolone where SC may be the culprit as this will contribute to mortality. SC may be sensitive or intermediate to enrofloxacin in vitro but is not effective in vivo. Lancefield Group G -hemolytic streptococci were isolated in large numbers from 6 dogs presented to the OVC. The group G streptococci identified in these dogs were distinguished from the human group G streptococcal strain. Isolates were highly sensitive to penicillin, erythromycin , clindamycin (occasional resistance is reported) or amoxicillin/clavulanate. Although SC was susceptible to penicillin in vitro, human studies have shown that where numbers of bacteria are high, penicillin may be ineffective. For this reason, the use of penicillin is not recommended. Clindamycin's efficacy is not affected by inoculum size or stage of growth, it is a potent suppressor of bacterial toxin synthesis and facilitates phagocytosis of the streptococcal organism by inhibiting M-protein synthesis, it suppresses synthesis of penicillin-binding proteins which are also involved in cell wall synthesis and degradation. Clindamycin has a longer postantibiotic effect than -lactam antibiotics such as penicillin and it causes suppression of lipopolysaccharde-induced monocyte synthesis of tumour necrosis factor. Streptococcal pyrogenic toxins A and B induce human mononuclear cells to synthesize TNF- and IL-6 which could mediate the fever, shock and tissue injury observed in patients with STSS. The M-protein contributes to invasiveness by impeding phagocytosis of the organism by polymorphonuclear leukocytes. In human patients with STSS associated with NF refractory to antibiotic therapy and local debridement, IV human immunoglobulin resulted in successful treatment of the disease.
With rapid diagnosis and treatment, the prognosis is good for NF, however, the extent of disease greatly influences outcome.
References
- DL. Stevens. Streptococcal Toxic-Shock syndrome: Spectrum of disease, pathogenesis and new concepts in treatment. Emerging Infectious diseases. 1995;1(3):69-78.
- CW Miller, JF Prescott, KA Mathews et al. Streptococcal toxic shock syndrome in dogs. J Am Med Assoc. 1996;209(8):1421-1426.
- KA Mathews, AG Binnington. Management of wounds using honey. Compendium Cont Edu for Pract Vet 2002; 24(1):53-60. Review article.
- KA Mathews, AG Binnington. Management of wounds using sugar.Compendium Cont Edu for Pract Vet 2002; 24(1):41-50. Review article.
|
