Alfaxalone compared with ketamine for induction of anaesthesia in horses following xylazine and guaifenesin.

The research study compares the effectiveness of two anesthetic drugs, alfaxalone and ketamine, in horses that had been premedicated with xylazine and guaifenesin. The study found both drugs to be effective at inducing anesthesia, but noted a higher incidence of muscle tremors with the use of alfaxalone. However, there were no significant differences between the two in terms of cardiopulmonary responses or recovery quality.

Research Methodology

• The study involved six adult horses – five Standardbreds and one Thoroughbred, which included two mares and four geldings.
• This was a randomized, blinded, cross-over experimental study in which each horse, on different occasions, was induced with either ketamine or alfaxalone after being premedicated with xylazine and guaifenesin.
• Parameters such as incidence of tremors or shaking after induction, recovery and ataxia on recovery were scored and time to recovery was recorded.
• Vital signs such as arterial blood pressures, heart rate and respiratory rates were monitored before premedication and at intervals during anesthesia.

Results

• No difference was found in the recovery quality or ataxia scores between the two drugs.
• However, horses administered with alfaxalone showed a higher incidence of tremors or shaking on induction compared to those given ketamine.
• Recovery time to standing was similar for both drugs, though it took longer for horses to recover enough to return to the paddock after being given alfaxalone as compared to ketamine.
• There were no significant differences between the effects of the two drugs on heart rate, blood oxygen pressure, and carbon dioxide pressure. However, for both regimens, oxygen pressure decreased with respect to values taken before premedication.
• Both treatments showed no different effect on blood pressure.

Conclusion

• This study suggests that both alfaxalone and ketamine are effective in inducing anesthesia in horses, despite more instances of muscle tremors observed with alfaxalone during induction.
• Since no major differences were observed in cardiopulmonary responses or the quality of recovery, and only minor differences in recovery times, the study concludes that both agents are suitable for use following the premedication regimen used in this study.