Effects of ketamine, midazolam and methadone, combined with local anesthesia, in cats undergoing orchiectomy

Different anesthetic combinations are used for orchiectomy in cats. This study aimed to evaluate the anesthetic and cardiopulmonary effects on the physiological variables of ketamine (10 mg/kg), midazolam (0.2 mg/kg) and methadone (0.3 mg/kg), combined with local anesthesia, in cats undergoing orchiectomy (n = 19 cats). The time for lateral recumbency, degree of sedation, muscle relaxation and nociception were recorded preoperatively. The propofol rescue dose was recorded. The time to head up and quality of recovery were evaluated postoperatively. The time for lateral recumbency was 5 ± 2 minu-tes. Fifteen minutes after the administration of the ketamine-midazolam-methadone combination, a greater sedative effect, muscle relaxation and less response to noxious stimulation were observed. Propofol was administered to twelve cats under local anesthesia, at a total dose of 1.5 ± 0.8 mg/kg. Surgery was started 28 ± 5 minutes after the administration of ketamine--midazolam-methadone combination. There were no differences in the physiological variables evaluated over the other evalu-ation times (p > 0.05). The recovery quality scores were adequate, and the time to head up was 51 ± 10 minutes. Under the conditions of this study, the ketamine-midazolam-methadone combination did not allow local anesthesia for orchiectomy. Many cats required propofol rescue prior to surgery. This combination promoted minimal changes in physiological variables and prolonged anesthetic recovery.