Effect of intravenous administration of tramadol on the minimum alveolar concentration of isoflurane in dogs

Abstract

This study was aimed to evaluate the effects of tramadol hydrochloride on the minimum alveolar concentration of isoflurane (MACISO) in dogs. Six healthy, female German shepherd dogs (aged 1-2 years) were used in this study. Anesthesia was induced by mask induction and maintained with isoflurane in oxygen. Mechanical ventilation maintained the end-tidal CO2 partial pressure (PETCO2) from 35 to 45 mmHg throughout the study. A baseline MACISO (MACISOB) was determined starting 45 minutes after induction of anesthesia by clamping a pedal digit until gross purposeful movement was detected. After MACISOB determination, dogs received a tramadol loading dose of 3 mg/kg followed by a continuous rate infusion (CRI) of 2.6 mg/kg/h. The determination of MACISO after administration of tramadol (MACISOT) began 20 min after the start of the CRI. Arterial blood pressure and heart rate were recorded continuously and arterial blood samples for blood gas analysis were collected at the end of the equilibration period. Mean ± SD values for the MACISOB and MACISOT were 1.33 ± 0.04% and 1.23 ± 0.04%, respectively. The MACISOB decreased significantly by 7.5 ± 0.2% (P < 0.05) after administration of tramadol. The mean heart rate and arterial blood pressure of six dogs were not changed significantly after tramadol administration. The blood gas levels remained constant during the study. In conclusion, tramadol could significantly reduce MACISO without depression of cardiorespiratory function. Thus, the use of tramadol on inhalation anesthesia with isoflurane in dogs can improve the stability of anesthesia and the quality of recovery. ? 2015 Korean Society of Veterinary Clinics. All rights reserved.