Effects of atipamezole dosage and timing of administration on recovery time and quality in cats following injectable anaesthesia incorporating ketamine

Objectives The aim of this study was to establish the optimum dosage and timing of administration of atipamezole in cats undergoing general anaesthesia incorporating ketamine to provide the shortest recovery possible without unacceptably compromising recovery quality. Methods In total, 128 healthy male cats (age range 2-108 months, weight range 0.56-5.22 kg) admitted for castration were randomly allocated to groups of 32. Anaesthesia was induced with 60 mg/m(2) ketamine, 180 mu g/m(2) buprenorphine, 3 mg/m(2) midazolam and 600 mu g/m(2) medetomidine intramuscularly (IM). Cats received 600 mu g/m(2) (groups 1ATI20 and 1ATI40) or 1.5 mg/m(2) (groups 2.5ATI20 and 2.5ATI40) atipamezole IM either 20 (groups 1ATI20 and 2.5ATI20) or 40 mins (groups 1ATI40 and 2.5ATI40) after the 'quad'. Preparation time, surgical time, auricular temperature, times to sternal recumbency and first standing, and recovery quality score were recorded. Data were analysed using ANOVA, Kruskal-Wallis, Mann-Whitney U-tests and chi(2) tests. Statistical significance was deemed to be P <= 0.05. Results Groups did not differ significantly in preparation or surgical time. Auricular temperature decreased significantly over time (P <0.01) but did not differ between atipamezole treatment groups. Time to sternal recumbency in group 2.5ATI20 (52.9 +/- 22.3 mins) was faster than group 1ATI20 (65.7 +/- 24.7 mins) (P <= 0.05), but there were no significant differences between other groups. Time to first standing and recovery quality scores did not differ significantly between groups. Minimal adverse effects were seen. Conclusions and relevance Atipamezole administration after 20 mins did not reduce recovery time but neither was recovery quality adversely affected compared to when administered after 40 mins following datasheet recommendations with concurrent ketamine administration. The results of this study also suggest that an atipamezole:medetomidine dose ratio of 2.5:1 is more effective than 1:1 in reducing recovery time, regardless of timing of administration, although this only reached statistical significance for time to sternal recumbency when atipamezole was administered after 20 mins.