Abstract
For evaluation of the combination of medetomidine and butorphanol as a preanesthetic medication, 137 dogs were premedicated with an intravenous injection of 0.005 mg/kg medetomidine with 0 (n=29), 0.0125 (n=25), 0.025 (n=26), 0.05 (n=30), or 0.1 (n=27) mg/kg butorphanol. In all dogs, anesthesia was induced by an intravenous injection of 5.0 mg/kg ketamine, followed by intratracheal intubation and inhalation anesthesia with nitrous oxide-oxygen-sevoflurane. The adequate sedative effect and muscular relaxation were induced in all dogs. The sedative effect of medetomidine was enhanced by the combination with butorphanol. In all dogs, bradycardia was observed immediately after premedication. No vomiting was observed in dogs premedicated with the combination of medetomidine and butorphanol, while 4 of 29 (13.8%) dogs premedicated with medetomidine alone vomited after premedication. Respiratory depression was notable after intubation, particularly in dogs premedicated with the combinations of 0.005 mg/kg medetomidine and 0.05 or 0.1 mg/kg butorphanol. The end-expiratory concentration of sevoflurane during surgery was not reduced by butorphanol. Mean arterial blood pressure was maintained around 100 mmHg in all dogs, although heart rate was decreased dose dependently by butorphanol after intubation. The combination of medetomidine and butorphanol was useful to enhance the sedative effect of medetomidine and to prevent vomiting induced by medetomidine. The combination of 0.005mg/kg medetomidine and 0.025 mg/kg butorphanol is adequate as an intravenous preanesthetic medication.
