Comparison of four drug combinations for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis

Objective-To evaluate anesthetic effects of 4 drug combinations used for to tal intravenous anesthesia of horses undergoing surgical removal of an abdo minal testis. Design-Clinical trial. Animals-32 healthy cryptorchid horses. Procedure-Horses were sedated with xylazine and butorphanol and were random ly assigned to 1 of 4 groups: induction of anesthesia with ketamine and dia zepam and maintenance with bolus administration of ketamine and xylazine (K D/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and mainte nance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infus ion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minute s were administered an inhalant anesthetic, and data from these horses were excluded from analysis. Results-Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthet ized with TKD had a significantly greater number of attempts to stand, comp ared with the other groups, and mean quality of recovery from anesthesia fo r horses in the TKD group was significantly worse than for the other groups . Anesthesia, surgery, and recovery times were not significantly different among groups. Conclusions and Clinical Relevance-Results suggest that all 4 drug combinat ions can be used to induce short-term anesthesia for abdominal cryptorchide ctomy in horses. However, horses receiving TKD had a poorer recovery from a nesthesia, often requiring assistance to stand.