Sedation with xylazine and lumbosacral epidural administration of lidocaine and xylazine for umbilical surgery in calves

OBJECTIVE: To determine whether anesthesia consisting of sedation induced by intramuscular administration of xylazine hydrochloride and lumbosacral analgesia induced by epidural administration of lidocaine and xylazine is useful for umbilical surgery in neonatal calves. DESIGN: Prospective study. ANIMALS: 6 neonatal male dairy calves. PROCEDURE: Calves were sedated with xylazine (0.1 mg/kg [0.045 mg/lb] of body weight, i.m.), and 5 minutes later a 2% solution of lidocaine (0.18 to 0.24 ml/kg [0.08 to 0.11 ml/lb]) and xylazine (0.05 mg/kg [0.022 mg/lb]) were administered into the lumbosacral epidural space. Calves were positioned in dorsal recumbency, and the umbilical structures were resected. Local infusion of lidocaine, cranial to the umbilicus, was required in 5 of 6 calves to provide adequate analgesia. Xylazine sedation was reversed with tolazoline (1 mg/kg [0.45 mg/lb], i.v.). RESULTS: Calves maintained adequate cardiac output and oxygen delivery throughout the procedure but were hypotensive. Reversal of xylazine-induced sedation with tolazoline caused transient sinus bradycardia and sinus arrest, accompanied by severe systemic arterial hypotension. All calves regained a suckle reflex within 10 minutes and were able to stand within 90 minutes. CLINICAL IMPLICATIONS: Intramuscular administration of xylazine for sedation and epidural administration of lidocaine and xylazine for analgesia failed to provide satisfactory analgesia for umbilical resection without supplemental local infiltration of lidocaine. The anesthetic protocol is most useful when respiratory compromise or cost are concerns and the surgical procedure can be completed in < 1 hour. Caution should be exercised when tolazoline is administered intravenously to reverse xylazine-induced sedation in calves.