Effect of Butorphanol-Medetomidine and Butorphanol-Dexmedetomidine on Echocardiographic Parameters during Propofol Anaesthesia in Dogs.

This study compared the effects of butorphanol-medetomidine and butorphanol-dexmedetomidine combinations on echocardiographic parameters during propofol anaesthesia in dogs. The dogs were randomly divided into two groups. In the butorphanol-medetomidine (BM) group, butorphanol (0.2 mg/kg) and medetomidine (15 μg/kg) were intravenously administered; in the butorphanol-dexmedetomidine (BD) group, butorphanol (0.2 mg/kg) and dexmedetomidine (7.5 μg/kg) was used. Anaesthesia was induced with propofol and maintained with a constant-rate infusion of propofol (0.2 mg/kg/min). The echocardiographic parameters were assessed in conscious dogs (T). Echocardiography was conducted again at 10 min post premedication (T), followed by assessments at 30 (T), 60 (T), and 90 (T) mins. The dogs were subjected to diagnostic procedures (radiography, computed tomography) under anaesthesia. A significant reduction in heart rate and cardiac output was noted in both groups at T. There was no significant difference in the stroke volume between the BM and BD groups. The application of butorphanol-dexmedetomidine caused a significant increase in the left ventricular internal diameter in diastole and the diameter of the left atrium compared to that caused by butorphanol-medetomidine. This study documented that butorphanol-medetomidine and butorphanol-dexmedetomidine combinations caused similar reductions in heart rate and cardiac output in both groups. 'New´ valvular regurgitation occurred following their administration.