Clinical evaluation of xylazine, lidocaine and ketamine intravenous infusion to reduce isoflurane requirement in Thai native cross-bred ponies

Abstract

Balanced anesthesia in equine could reduce anesthetic-related fatalities. Sedative, anesthetic and analgesic agents currently available in Thailand such as xylazine, ketamine, isoflurane and lidocaine are extensively used in equine practice, but their combination has not been reported. The present study aimed to determine the minimum alveolar concentration (MAC) of isoflurane and clinical parameters in Thai native cross-bred ponies under general anesthesia. Six Thai native cross-bred ponies were examined by a random crossover method. They were categorized into 4 groups according to the maintenance of anesthesia which were isoflurane group (I), isoflurane and lidocaine group (IL), isoflurane, xylazine and ketamine group (IXK) and isoflurane, xylazine, lidocaine and ketamine group (IXKL). Tranquilization was performed with acepromazine (0.04 mg/kg IV), and sedation was performed with xylazine (0.8 mg/kg IV). Anesthesia was induced with ketamine (2 mg/kg IV) and diazepam (0.1 mg/kg IV), and maintained with isoflurane in oxygen and a constant rate infusion (CRI) of injectable drugs. Measurement parameters were heart rate (HR), respiratory rate (RR), mean arterial blood pressure (MAP), blood gases variables (pH, PaO2, PaCO2), end-tidal isoflurane concentration (ET-iso), end-tidal carbon dioxide concentration (ET-CO2), MAC and recovery scores. The MAC of isoflurane (mean±SD) in groups I, IL, IXK and IXKL were 0.74±0.2%, 0.67±0.2%, 0.45±0.2% and 0.16±0.1%, respectively. A significant (p<0.05) reduction of 78% was found when compared between groups I and IXKL. There was no significant difference in the blood gases variables and recovery scores in all groups. In conclusion, the loading dose of xylazine 0.8 mg/kg followed by infusion of 0.5 mg/kg/h, ketamine 2 mg/kg followed by infusion of 1 mg/kg/h, and lidocaine 1.5 mg/kg within 15 minutes followed by 50 μg/kg/min, combined with isoflurane could reduce isoflurane requirement in Thai native cross-bred ponies with good recovery quality.