Comparison of two different doses of xylazine and ketamine versus medetomidine for partial intravenous anaesthesia in horses

Abstract

Thirty horses were randomly divided into three groups and sedated with xylazine (1.1 mg/kg). General anaesthesia was induced with diazepam (0.03 mg/kg) and ketamine (2.5 mg/kg). Partial intravenous anaesthesia was maintained with isoflurane and constant rate infusion (CRI) consisting of xylazine 0.33 mg/kg/h and ketamine 1.5 mg/kg/h (X+K); or, higher dose of xylazine 1.2 mg/kg/h and ketamine 3.6 mg/kg/h (XX+KK); or, medetomidine 3.5 μg/kg/h (MED). Horses in each group breathed spontaneously. Heart rate, respiratory rate, peripheral oxygen saturation, palpebral and corneal reflexes, rescue doses with ketamine, invasive arterial blood pressure, inspired and expired gas compositions were measured. Anaesthesia, surgery, and recoveries were timed, and recovery was scored. The xylazine with ketamine groups showed a higher respiratory rate, a significant decrease in consumption of isoflurane, and a shorter time to standing in comparison with the medetomidine group. Recovery of the lowest quality was observed in group MED and a significantly improved recovery was observed in group X+K. The CRI consisting of xylazine with ketamine was shown to be a suitable alternative to CRI with medetomidine in horses undergoing arthroscopy.