Assessment of unassisted recovery from repeated general isoflurane anesthesia in horses following post-anesthetic administration of xylazine or acepromazine or a combination of xylazine and ketamine.

This research investigates the effects of post-anesthetic administration of different drugs on the quality and timing of recovery from repeated general isoflurane anesthesia in horses, finding that horses generally improve the quality of recovery during consecutive anesthetics regardless of the used sedative.

Study Design

The study was designed as a prospective, randomized, crossover trial. It involved 15 adult research horses, aged 6.5±3.4 years and weighing approximately 499±40 kg. Each horse underwent three separate anesthetic episodes with isoflurane as part of a magnetic resonance procedure on their forelimbs. Upon waking, they were given acepromazine, xylazine, or a combination of xylazine and ketamine in a randomized order. The researchers used a composite numerical rating and a general descriptive scoring system to evaluate and compare the recovery quality among the three treatment groups.

Results

• Recovery scores were better for horses given xylazine alone compared to those that received the combined xylazine/ketamine treatment. This superior performance was related to their movement to the sternal (chest-down) position, strength, and number of attempts to stand up.
• Horses given acepromazine showed similar recovery scores to those who received either xylazine alone or in combination with ketamine.
• The time taken to move to a sternal position and to remove the breathing tube following anesthesia was statistically longer for horses administered with xylazine. However, the time to stand was relatively the same across all treatments.
• The quality of recovery improved by the third anesthetic episode, notwithstanding the sedative administered. This was also connected to better scores for strength and number of standing attempts.

Conclusions

The findings revealed that xylazine showed superior outcomes compared to the combination of xylazine and ketamine, but its effectiveness was comparable to acepromazine. Furthermore, the study suggested that prior experience, particularly from recent anesthetics, may help horses in achieving better recovery. Despite the different sedatives used, the recovery quality was consistently good across all treatments. This study thus enhances our understanding of post-anesthetic recovery in horses and can be valuable in improving anesthesia practices in equine medicine.