Evaluation of the quality of the recovery after administration of propofol or alfaxalone for induction of anaesthesia in dogs anaesthetized for magnetic resonance imaging

Jimenez CP, Mathis A, Mora SS, et al. 

Vet Anaesth Analg 2012;39:151-159.

Objective To compare the quality of the recovery when propofol or alfaxalone were administered for the induction of anaesthesia in dogs undergoing neurological diagnostic procedures. Experimental design Prospective, randomized clinical trial. Animals Forty two client-owned dogs, 21 females and 21 males, weighing between 5.7 and 55 kg. Methods Each dog was sedated with methadone (0.2 mg kg(-1) intramuscularly or 0.1 mg kg(-1) intravenously). Sedation was scored after 30 minutes. Anaesthesia was induced either with propofol or alfaxalone, administered to enable orotracheal intubation, after which anaesthesia was maintained with sevoflurane in oxygen. At the end of the procedure, the animals recovered in the clinical area. Quality of recovery was scored (early recovery) using simple descriptive and visual analogue scales (SDS and VAS). When sternal recumbency was achieved, dogs were moved to the recovery room and recovery was scored again (late recovery). Quantitative data were assessed with the Mann-Whitney U test, Kruskal-Wallis test, Spearman’s rank correlation and Bland Altman plots as appropriate, whilst categorical data were analysed with the Chi square test and weighted kappa. Results Sex, behaviour and duration of anaesthesia did not influence recovery scores. Dogs had poorer late recovery scores in the alfaxalone group compared to the propofol group (SDS, p = 0.014; VAS, p = 0.017). Degree of sedation after premedication influenced assessed SDS scores during early (p = 0.038) and late recovery (p = 0.008) (dogs more heavily sedated recovered better). However by VAS scores, sedation did not statistically influence early recovery (p = 0.299) but did affect late recovery (p = 0.013). Rescue sedation (medetomidine) was required only in two dogs in the alfaxalone group. Conclusions Induction of anaesthesia with alfaxalone was associated with poorer recovery than with propofol in animals receiving premedication with methadone. Clinical relevance Greater attention to the recovery environment may be advisable when using alfaxalone for induction of anaesthesia where minimal premedication has been used. Further sedation in recovery may be required.