We read with interest the "Clinical Exposures" case report "A peritoneopericardial diaphragmatic hernia in a cat" in the April
2004 issue. While the diagnostic and surgical management of this case was excellent, the analgesic support was inadequate.
According to the authors, the only analgesic this cat received was butorphanol. It is not specified how far in advance of
surgery the cat received the butorphanol, but we are concerned that it might have been wearing off by the time of the procedure.
Current analgesic references suggest that butorphanol's analgesic duration of effect is, at most, one to three hours. The
cat in this report received only one postoperative injection of butorphanol, which allowed a total of two to six hours of
perioperative analgesia. The cat was discharged with instructions to receive oral butorphanol twice a day. The first-pass
effect and duration of action render this an inappropriate and ineffective analgesic in this case.1
Certainly, butorphanol is good for mild to moderate visceral pain in cats and has low cardiac and respiratory depressive effects,
but adding a pure mu agonist such as hydromorphone, oxymorphone, morphine, or fentanyl, or even a partial mu agonist such
as buprenorphine, would have been much more appropriate and effective. Additional considerations could have included adding
an NMDA antagonist, such as a continuous-rate infusion of ketamine, during the perioperative period and an NSAID such as meloxicam
for postoperative pain relief. The multimodal approach to pain control is important for us to consider.
Our feline patients are good at hiding pain, having evolved to do so in order to avoid predation. It behooves us as our patients'
advocates to use appropriate analgesia based on current knowledge of drugs and the pain process rather than the habits of
what has been done in the past. Mere survival is no longer an adequate measure of anesthetic success. Rather, minimizing morbidity
needs to be considered.
We were also taken aback by the lack of mention of supportive care or monitoring of this cat. We assume these were done, but
it would be useful to include these details.
1. Lascelles, B.D.X.; Robertson, S.A.: Use of thermal threshold response to evaluate the antinociceptive effects of butorphanol
in cats. AJVR 65 (8):1085-1089; 2004.
1. Gaynor, J.S.; Muir, W.: Handbook of Veterinary Pain Management. Mosby, St. Louis, Mo., 2002.
2. Tranquilli, W.J. et al.: Pain Management for the Small Animal Practitioner. Teton NewMedia, Jackson, Wyo., 2000.
3. Mathews, K.A.: Pain assessment and general approach to management. Vet. Clin. North Am. (Small Anim. Pract.) 30(4):729-755; 2000.
4. Lamont, L.A.: Feline perioperative pain management. Vet. Clin. North Am. (Small Anim. Pract.) 32 (4):747-763; 2002.
5. Paddleford, R.R.: Preanesthetic agents. Manual of Small Animal Anesthesia. W.B. Saunders, Philadelphia, Pa., 1999; pp 12-30.
6. Wagner, A.E. et al.: Myths and misconceptions in small animal anesthesia. JAVMA 223 (10):1426-1432; 2003.
Angela Dyer, DVM
Penasquitos Pet Clinic
9728 Carmel Mountain Road, Suite E
San Diego, CA 92024
Robert Stein, DVM
Amherst Small Animal Hospital
2177 Kensington Ave.
Snyder, NY 14226
Kerrin Hobin, DVM
Harbor Veterinary Hospital
2202 Soquel Ave.
Santa Cruz, CA 95062
Twelve additional veterinarians signed this letter.