Clinical comparison of alfaxalone, ketamine and propofol following medetomidine and methadone in dogs.

OBJECTIVE: To compare the clinical effects of alfaxalone, ketamine and propofol in dogs following premedication with medetomidine and methadone.

STUDY DESIGN: Prospective, 'blinded' and randomized clinical study.

ANIMALS: A total of 75 male dogs presented for neutering at a charity clinic.

METHODS: Dogs were allocated to be administered alfaxalone, ketamine or propofol following premedication with medetomidine (20 μg kg-1 ) and methadone (0.2 mg kg-1 ). Dogs were temperament scored prior to premedication. Quality of sedation, induction of anaesthesia, recovery and recovery environment were scored by simple descriptive scales. Physiological variables during anaesthesia were recorded. Continuous numerical data were analysed using analysis of variance with repeated measures as necessary. Nonparametric data were analysed using Kruskal-Wallis tests and multiple comparisons using Dunn's test. Statistical significance was set at p < 0.05.

RESULTS: The mean (± standard deviation) dose of alfaxalone was 0.6 ± 0.2 mg kg-1 , that for ketamine was 1.5 ± 0.7 mg kg-1 and that for propofol was 0.8 ± 0.3 mg kg-1 . Alfaxalone inductions were significantly smoother compared to ketamine but not to propofol. Only one of 75 of the inductions was deemed poor. There were no differences in cardiopulmonary variables between groups except immediately after induction of anaesthesia. There were no differences in quality of recovery between groups.

CONCLUSIONS AND CLINICAL RELEVANCE: All three induction agents provided reliable, predictable anaesthesia conditions that were clinically indistinguishable and ideal for teaching anaesthesia skills. The medetomidine and methadone premedication resulted in profound, heavy sedation and the quality of induction of anaesthesia was better with alfaxalone compared to ketamine. No significant difference in induction quality was detected between alfaxalone and proprofol or propofol and ketamine, and these findings are likely to be of limited clinical significance when choosing an induction agent.