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 immediately before anesthesia and to determine whether prior exercise affects anesthesia induction, recovery, or both. Animals - 6 healthy Thoroughbreds in good condition and trained to run on a treadmill, each horse serving as its own control. Procedure - Horses ran on a treadmill until fatigued, then were sedated immediately with detomidine hydrochloride and anesthetized with a zolazepam hydrochloride-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, plasma lactate concentration, arterial pH, and PaCO₂ were significant. Plasma ionized calcium concentration was lower after exercise, compared with baseline values, and remained lower at 30 minutes of isoflurane anesthesia. Compared with baseline values, plasma chloride concentration decreased significantly during anesthesia after exercise. Cardiac output during anesthesia was significantly lower than that during preexercise, but significant differences between experimental and control periods were not observed. Arterial blood pressure during anesthesia was significantly lower than that during preexercise and initially was maintained better during isoflurane anesthesia after exercise. Cardiac output and blood pressure values were clinically acceptable throughout anesthesia. Conclusion - Administration of detomidine hydrochloride followed by zolazepam hydrochloride-tiletamine appeared to be safe and effective for sedation and 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 injured horses.