Features of feline anesthesia and pain management (Proceedings)

Coexisting Disease and Special Considerations

• Hyperthermia

• HCM

• 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.

NSAIDs to Avoid in Cats

• Aspirin

• Ibuprofen

• Indomethacin

• Naproxen

• Acetaminophen!!!

All are extremely toxic in cats.13 year old cat can no longer jump on the bathroom counter to get a drink.

What are your comments on the best practice treatments for arthritis in cats? (Recent lab work was normal)

Our cat, Don Juan is a 13.5 neutered male cat that weighs 13 pounds and his body score is 5/9.

One recommendation: "Adequan first (5 mg/kg sq, 2X weekly X 2 wks, then once weekly X 2 weeks, then every other week X 4 wks, then monthly long term). We sell a whole bottle to the client and teach them to give injections at home, give them a check sheet, etc. The results are usually dramatic! If that does not help, then we turn to other/additional interventions." (Ben Leavens, DVM Ron Tenney, DVM)

Buprenorphine for Cats

• Excellent oral transmucosal availability in cats

o (not quite as complete in dogs)

o Nice to send home for post-op analgesia in cats, often with meloxicam.

• Long duration of action

• Ceiling effect on respiratory depression, but perhaps not on analgesic effect

• Slow onset of analgesia and sedation, even after IV administration

Lidocaine CRI in Cats

• Anesthetic and analgesic effect only at high doses approaching toxicity

• Therefore usually not worth including - with a few exceptions

Propofol Toxicity in Cats

• 2,6, di-isopropyl phenol

• Phenol toxicity upon repeated or continuous use

• Propofol is still a very useful anesthetic for cats - with some limitations

Feral Cat Neuters and Spays

• Large production, assembly (disassembly) line scale, minimal costs and maximum yields, volunteer staff, strict protocols (Dr. Julie Levy, et al.)

Our own Feral Fixin's program

• TKXBup + Meloxicam

Principles in Pain Management

Preemptive Analgesia

• Pre operative analgesics (as well as post op)

Balanced Analgesia

• Combined multi-modal strategies

• (opioids, locals, dissociatives, NSAIDs)

Dose to Effect

• "Give until it helps"

• Respond to individual needs

Recognition of Clinical Pain in Cats

Behaviors as Potential Indicators of Pain in the Cat

• Poor or lack of grooming

• Hissing or aggression if the painful part is manipulated

• Tendency to hide the painful part and look normal

• Dissociation from the environment

• Vocalization is rare

Pain Scales: Visual Analog Scale (VAS)

• Use of the VAS to evaluate pain management

• Scale of no pain to worst pain ever, 0-100 mm

Benefits of Pain/Stress Management

• Reduced sympathetic stimulation

o Better control of cardiovascular function

o Reduced neurologic stimluation

o (maladaptive neuro-endocrine response, particularly for the critically ill and severely injured)

• Improved eating & drinking

• Improved general well being

Epidural Analgesia in Cats

• More caudal cord termination and a smaller LS space than in dogs

• Duramorph

o Preservative-free morphine

o 0.1 mg/kg

• Marcaine

o Bupivacaine

o (q.s. 0.2 ml/kg)

o "selective block"

o augments opioid

Force Plate Evaluation of Pain and Analgesia in Cats

• Eval transderm fentanyl...onychectomy. J. Franks, et.al, JAVMA, 217, 1013, 2000.

Distal Limb Blocks for Declaw Analgesia:

• Median nerve

• Ulnar nerve

o Palmar branch

o Dorsal branch

• Radial nerve

o Superficial branches

• "Ring block" at carpus serves the same purpose