Comparison of ketamine and alfaxalone for induction and maintenance of anaesthesia in ponies undergoing castration.

The study compared the efficacy of ketamine and alfaxalone as anaesthetic drugs in ponies undergoing castration. The results showed that alfaxalone had shorter induction times, but both drugs, overall, provided an acceptable level of anaesthesia for the procedure.

Introduction and Methodology

• The text describes a prospective, randomized, blinded clinical study carried out on forty-two Welsh Mountain ponies, each of which was a year old.
• The purpose was to compare the effectiveness and rapidity of two anaesthetic agents, Alfaxalone and Ketamine, for use in total intravenous anaesthesia in ponies that were subjected to castration.
• The ponies were randomly assigned to receive one of the two agents.
• To sedate the animals before the actual induction of anaesthesia, a combination of Romifidine and Butorphanol was administered intravenously. The progress of sedation and the response to tactile stimulation were scored. If the sedation was found to be insufficient, an additional dose of Romifidine was given.
• The anaesthesia was induced with either Ketamine or Alfaxalone, based on the assigned treatment. Both these agents were combined with Diazepam and were administered intravenously.

Observations and Data

• The time taken for the ponies to move to lateral recumbency (lying on their side) after the injection of the anaesthetic was recorded.
• To monitor the effectiveness of the anaesthetic agents, descriptive scores were used to assess the quality of induction, the conditions of surgery and recovery.
• If the ponies showed any movement during the procedure, additional doses of Ketamine or Alfaxalone were administered.
• The recovery times to first head lift, sternal recumbency (lying on the chest), and stand were recorded, along with the number of attempts needed for each.

Results and Conclusion

• Both the anaesthetic agents yielded similar sedation, induction, and surgical scores.
• However, ponies anaesthetised with Alfaxalone showed shorter induction times (average 18 seconds) than those anaesthetised with Ketamine (average 30 seconds).
• Of all ponies, only three required additional sedation. Moreover, the need for additional doses was higher in animals receiving alfaxalone (seven ponies) compared to ketamine (four ponies).
• Recovery scores (scale 1-4, lower being better) differed between groups, suggesting that there was a statistically significant difference, albeit slight, in the quality of recovery between Ketamine and Alfaxalone.
• No differences were detected in the actual duration of anaesthesia or in the speed of recovery after the end of surgery.

Based on these findings, the study concludes that both Ketamine and Alfaxalone provide an acceptable quality of anaesthesia. However, Alfaxalone had shorter induction times, which suggests it may have some advantages over Ketamine in specific circumstances.