Comparison of acepromazine, midazolam and xylazine as preanaesthetics to ketamine-isoflurane anaesthesia in horses

The present study was conducted on 13 horses to evaluate the use of xylazine, acepromazine and midazolam as preanaesthetics for ketamine-isoflurane anesthesia. The animals were randomly divided into three groups having at least four animals each. In group I (n=4) sedation was accomplished by administering acepromazine (0.04 mg/kg), in group II (n=4) midazolam (0.2 mg/kg) was used and in group III (n=5) xylazine was administered (1.1 mg/kg). Induction of anaesthesia was done by ketamine (2.2 mg/kg) and maintenance by 2.5–4% isoflurane in all groups. The groups were compared on the basis of clinicophysiological, acid-base and electrolyte parameters. Analgesia and muscle relaxation were adequate in all groups during maintenance. Although respiratory acidosis was seen in all groups, the values returned to normal postoperatively. Xylazine was found to be a better premedication agent in terms of clinicophysiological, acid-base and electrolyte status as compared to midazolam or acepromazine. All the drug combinations were found safe in horses. Xylazine-ketamine-isoflurane combination could be recommended for surgery requiring longer duration of anaesthesia because of good sedation, moderate analgesia and excellent muscle relaxation along with smooth recovery.