Anesthesia of horses with a combination of detomidine, zolazepam, tiletamine, and isoflurane immediately after strenuous treadmill exercise

Objectives-To evaluate effects of strenuous exercise in adult horses immedi ately before anesthesia and to determine whether prior exercise affects ane sthesia induction, recovery, or both. Animals-6 healthy Thoroughbreds in good condition and trained to run on a t readmill, each horse serving as its own control. Procedure-Horses ran on a treadmill until fatigued, then were sedated immed iately with detomidine hydrochloride and anesthetized with a zolazepam hydr ochloride-tiletamine combination. Anesthesia was maintained with isoflurane in oxygen for another 90 minutes. Blood samples were taken before, during, and after exercise and during anesthesia. Results-During exercise, changes in heart rate, core body temperature, plas ma lactate concentration, arterial pH, and PaCO2 were significant. Plasma i onized calcium concentration was lower after exercise, compared with baseli ne values, and remained lower at 30 minutes of isoflurane anesthesia. Compa red with baseline values, plasma chloride concentration decreased significa ntly during anesthesia after exercise. Cardiac output during anesthesia was significantly lower than that during preexercise, but significant differen ces between experimental and control periods were not observed. Arterial bl ood pressure during anesthesia was significantly lower than that during pre exercise and initially was maintained better during isoflurane anesthesia a fter exercise. Cardiac output and blood pressure values were clinically acc eptable throughout anesthesia. Conclusion-Administration of detomidine hydrochloride followed by zolazepam hydrochloride-tiletamine appeared to be safe and effective for sedation an d anesthesia of horses that had just completed strenuous exercise. Clinical Relevance-Anesthetic given in accordance with this protocol can be used to anesthetize horses that are injured during athletic competition to assess injuries, facilitate first aid, and possibly allow salvage of injur ed horses.