Alfaxalone in cyclodextrin for induction and maintenance of anaesthesia in ponies undergoing field castration.

Objective: To evaluate the induction and maintenance of anaesthesia using alfaxalone following pre-anaesthetic medication with romifidine and butorphanol in ponies undergoing castration in the field.

Study Design: Prospective clinical study.

Animals: Seventeen male ponies weighing 169 +/- 29 kg.

Methods: The ponies were sedated with romifidine and butorphanol intravenously (i.v.). Induction time was recorded following administration of alfaxalone 1 mg kg(-1) and diazepam 0.02 mg kg(-1) i.v.. If movement during surgery occurred, alfaxalone 0.2 mg kg(-1) was administered i.v.. The quality of anaesthetic induction, and recovery were scored on a subjective scale of 1 (good) to 5 (poor). The number of attempts to attain sternal recumbency and standing, quality of recovery and times from induction to end of surgery, first head lift, sternal recumbency and standing were recorded.

Results: Induction quality was good [median score (range) 1 (1-3)] with a mean +/- SD time of 29 +/- 6 seconds taken to achieve lateral recumbency. Ten ponies required incremental doses of alfaxalone during surgery. Mean times to the end of surgery, first head lift, sternal recumbency and standing were 26 +/- 9 minutes, 31 +/- 9 minutes, 33 +/- 9 minutes and 34 +/- 9 minutes respectively. The number of attempts to attain sternal recumbency was 1(1-1) and to attain standing was 1(1-2). Quality of recovery was good, with a recovery score of 1(1-2).

Conclusions And Clinical Relevance: Alfaxalone provided smooth induction and recovery characteristics and was considered suitable for maintenance of anaesthesia for castration in ponies.