Effects of intratesticular and incisional local anesthetic administration for castration of alpacas anesthetized with intramuscular ketamine-xylazine-butorphanol

Abstract

Objective: To determine the effects of intratesticular and incisional injection of local anesthetics on response to castration, surgical ease, and recovery in alpacas. Study Design: Prospective, blinded, randomized, and clinical trial. Animals: Intact male alpacas (n=38). Methods: Alpacas were anesthetized with intramuscular butorphanol, ketamine, and xylazine (BKX). Once recumbent, alpacas were instrumented with electrocardiogram, pulse oximeter, oscillometric blood pressure, and capnography. Heart rate (HR), respiratory rate (RR), and blood pressure (BP) were recorded every minute. Treatment drug (lidocaine, bupivacaine, or saline) was infiltrated along the incision and into both testicles followed by a prescrotal closed castration. Timing of major events, presence of movement during the procedure, need for additional anesthesia, and ease of surgery were recorded. Alpacas were administered postoperative oral meloxicam and assessment was made 24hours after recovery. Results: Median RR and mean BP (MBP) were lower in the lidocaine compared with the saline treated group. Median RR, HR, and MBP were significantly lower in the bupivacaine group compared with the saline group. Fewer alpacas displayed physical response to surgical stimulus with bupivacaine. No significant differences were found between groups for timing of events, need for additional anesthesia, ease of surgery, or postoperative assessment. Conclusion: Intratesticular local anesthetic blunts autonomic response and facilitates castration in alpacas anesthetized with BKX with minimal negative effects. Bupivacaine may have some benefit for local anesthesia during castration compared with lidocaine.