Evaluation of xylazine-alfaxalone anesthesia for field castration in donkey foals.

Objective: To evaluate the anesthetic and cardiopulmonary effects of xylazine-alfaxalone anesthesia in donkey foals undergoing field castration.
Study Design: Prospective clinical study.
Animals: A group of seven standard donkeys aged [median (range)] 12 (10-26) weeks, weighing 47.3 (37.3-68.2) kg.
Methods: Donkeys were anesthetized with xylazine (1 mg kg ^-1 ) intravenously (IV) followed 3 minutes later by alfaxalone (1 mg kg ^-1 ) IV. Additional doses of xylazine (0.5 mg kg ^-1 ) and alfaxalone (0.5 mg kg ^-1 ) IV were administered as needed to maintain surgical anesthesia. Intranasal oxygen was supplemented at 3 L minute ^-1 . Heart rate (HR), respiratory rate (f _R ) and mean arterial pressure (MAP) by oscillometry were recorded before drug administration and every 5 minutes after induction of anesthesia. Peripheral oxygen saturation (SpO ₂ ) was recorded every 5 minutes after induction. Time to recumbency after alfaxalone administration, time to anesthetic re-dose, time to first movement, sternal and standing after last anesthetic dose and surgery time were recorded. Induction and recovery quality were scored (1, very poor; 5, excellent).
Results: Median (range) induction score was 5 (1-5), and recovery score 4 (1-5). Overall, two donkeys were assigned a score of 1 (excitement) during induction or recovery. HR and MAP during the procedure did not differ from baseline. f _R was decreased at 5 and 10 minutes but was not considered clinically significant. SpO ₂ was <90% at one time point in two animals.
Conclusions and Clinical Relevance: Xylazine-alfaxalone anesthesia resulted in adequate conditions for castration in 12 week old donkeys. While the majority of inductions and recoveries were good to excellent, significant excitement occurred in two animals and may limit the utility of this protocol for larger donkeys. Hypoxemia occurred despite intranasal oxygen supplementation.
(Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)