Retrospective investigation of an association between high-dose buprenorphine and perpetuation of post-anesthesia hyperthermia in cats following ovariohysterectomy.

Objectives: We evaluated a potential association between the administration of high-dose buprenorphine and perpetuation of hyperthermia in cats following ovariohysterectomy (OVH). We hypothesized that buprenorphine 0.24 mg/kg subcutaneously (SC) would result in longer-lasting postoperative hyperthermia in cats vs a group receiving morphine 0.1 mg/kg SC.

Methods: Anesthetic records from cats admitted for OVH as part of surgical exercises for second year veterinary medicine students in 2018 and 2019 were collected. All cats were sedated with dexmedetomidine 20 µg/kg and morphine 0.1 mg/kg intramuscularly. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. At extubation, cats received morphine 0.1 mg/kg SC in 2018 and buprenorphine 0.24 mg/kg SC in 2019. Temperature was measured rectally prior to sedation, esophageally during anesthesia and rectally at 1, 4 and 16-20 h after extubation. Demographic data and temperature prior to administration of postoperative opioids were compared with -tests. The effects of treatment (opioids) and time on postoperative rectal temperature and on the incidence of hyperthermia (temperature >39.2°C) were evaluated with mixed and generalized linear mixed-effect models. Significance was set at <0.05.

Results: There were no differences in demographic characteristics between treatment groups (all  ⩾0.2). Intraoperative esophageal temperature was lower in cats scheduled to receive morphine (mean ± SD 36.6 ± 0.2) than in those receiving buprenorphine (36.9 ± 1.0) ( <0.0001). Postoperative temperature was higher for cats receiving buprenorphine than for those receiving morphine ( <0.0001). The incidence of hyperthermia 16-20 h after opioid administration was 56% for morphine and 73% for buprenorphine ( = 0.03).

Conclusions And Relevance: Buprenorphine 0.24 mg/kg SC for postoperative analgesia in cats was associated with hyperthermia that persisted for 16-20 h after administration, and the incidence of hyperthermia for this group was higher than in the cats that received morphine 0.1 mg/kg SC.