Comparison of Caudal Epidural Administration of Lidocaine and Xylazine to Xylazine/Ketamine Combination in Donkey (Equus asinus)

Objective- Evaulation of analgesic and sedative characteristics of xylazine/ketaminecombination for caudal epidural analgesia in comparison with two routine agents in donkey.Design- Cross over study.Animals- Five healthy adult donkeys of both sexes with body weights ranging from ۱۵۰-۲۰۰ kg.Procedures- Three treatments [lidocaine HCl ۲% (۰.۲۲ mg kg^-۱), xylazine HCl ۲% (۰.۱۷ mg kg^-۱) and xylazine HCl ۲% (۰.۱۷ mg kg^-۱) combined with ketamine HCl ۱۰% (۱ mg kg^-۱)] wereevaluated and animals received each of treatments randomly at one-week intervals.Cardiopulmonary parameters and rectal temperature were recorded before and every ۱۵ minutesafter epidural administration. The onset and duration of analgesia were evaluated every ۵minutes, using noxious stimulus (pin prick and pinch tests) on the skin of tail, perineum, anusand back thigh. Ataxia was assessed qualitatively between onset of anesthesia and return ofsensation. The data were analyzed using analysis of variance followed by Dunnett's test; a Pvalue<۰.۰۵ was considered significant.Results- Administration of xylazine along with ketamine resulted in more rapid onset and longerduration of analgesia (P<۰.۰۵), without any measurable cardiopulmonary side effects incomparison with the other treatments. However, severe ataxia was observed after the injection.Conclusion and Clinical Relevance- In a clinical point of view, despite early induction andlonger duration of analgesia, this combination at these doses is not suitable for standing surgeriesof hindquarters in donkey because there was unacceptable likelihood of recumbency.