Postanesthetic hyperthermia in cats: a retrospective comparison between hydromorphone and buprenorphin

Objective: To determine the prevalence of postanesthetic hyperthermia [rectal temperature > 40 degrees C (104 degrees F)] in a clinical population of cats. Study Design: Retrospective study. Animal Population: One hundred and twenty-five cats with an age range of 2 months to 16.1 years, and weighing 3.9 +/- 1.5 kg. Materials and Methods: Data were obtained from the medical records of 125 cats that underwent general anesthesia. Information on perioperative rectal temperatures, breed, sex, weight, surgical procedure, anesthetic time, surgery time, anesthetic and analgesic drugs were retrieved. Statistical Analysis: Five groups of cats were compared; group 1 (n = 15) received acepromazine and no opioids; group 2 (n = 17) received acepromazine and buprenorphine; group 3 (n = 19) received acepromazine, buprenorphine and ketoprofen; group 4 (n = 45) received acepromazine and hydromorphone and group 5 (n = 29) received acepromazine, hydromorphone and ketoprofen. Data conformed to a split-plot repeated measures analysis of variance and was analyzed using SAS PROC MIXED. Post hoc tests were by means of Bonferroni t-test; <= 0.05 was considered significant. Results: Rectal temperature was significantly decreased in all groups at the end of anesthesia. Rectal temperature was significantly elevated at 1, 1.5, 2, 3, 4 and 5 hours after the end of anesthesia in group 4, and at 2, 3 and 4 hours in group 5. Sixty-four percent of cats in group 4 and 69% in group 5 had rectal temperatures > 40 degrees C (104 degrees F) at one or more times in the postanesthetic period. The highest temperature recorded was 42.5 degrees C (108.5 degrees F) in one cat in group 4. Mean rectal temperature did not exceed the preoperative temperature at any time during the postanesthetic period in group 1, 2 and 3 animals. Conclusions: This study indicates an association between hyperthermia and perioperative administration of hydromorphone in cats. Clinical Relevance: When hydromorphone is used in cats their body temperature should be closely monitored.