Features of feline anesthesia and pain management (Proceedings)


Features of feline anesthesia and pain management (Proceedings)

Apr 01, 2009

Coexisting Disease and Special Considerations

• Hyperthermia
• Feral Cat Programs
• Peri-Operative Analgesia
o Declaw Pain

Metabolism of Drugs

• Cats have relatively deficient hepatic glucuronidation mechanism
• Fewer hepatic UDP-glucuroninosyltransferase (UGT) isoforms, perhaps due to strict carnivorous diet and lack of exposure to plants and phytoalexins
• Lack of morphine-6-glucuronide formation
• Toxicity of acetaminophen and other phenols and NSAIDs
• Anesthetic Hyperthermia in Cats
• Drugs and stressors implicated
• Some opioids implicated:
o hydromorphone, oxymorphone, fentanyl (Duragesic), morphine
• Dose dependent (±)
• Reversal of opioid with antagonists
• Symptomatic / Supportive treatment
o Vasodilation, sedation, active cooling
o Monitoring to avoid over-correction

Hypertrophic Cardiomyopathy

• Subclinical HCM is a nasty silent killer!
• It converts otherwise very safe and useful anesthetic techniques into a substantial threats to survival
• HCM plus ketamine or Telazol kills lots of cats! So can HCM plus isoflurane!
• No adequate and practical screening tests as yet.
• HCM is a failure of relaxation (lusitropy), rather than contraction
• Limited ventricular volume and limited coronary blood flow
• Priorities:
o slow heart rate
o maintain preload

Anesthetic Techniques for Cats with (suspected) HCM

• Minimize stress and excitement
• Avoid acepromazine (to maintain preload)
• Avoid anticholinergics
• Benzodiazepine (midazolam or diazepam, potential for excitement)
• Medetomidine (controversial ?) for HCM with LVOT obstruction
• Opioids (butorphanol, hydromorphone, buprenorphine, fentanyl)
• Propofol, Etomidate
• Halothane, Isoflurane (worst), Sevoflurane (best)
• Fluid therapy to maintain preload, but limited with any signs of heart failure
• Monitoring and Support

NSAIDs in Cats

• Meloxicam, 0.1 mg/kg, q24h. For 2-3 days mg/cat, oral suspension, one drop q24h)
• EU approved label for chronic administration of meloxicam in cats
• Ketoprofen, 1.0-2.0 mg/kg, SC, IM initially, then 0.5-1.0 mg/kg, PO, SC, q24h
• Carprofen, 1.0 mg/kg, PO, (1-2 doses only), q24h
• "Old School" - Aspirin in cats: "Just say NO!" Much longer dosing interval than in other species, leading to a greater risk of overdose (due to error) and greater toxicity than in dogs. Better options.