Hemodynamic effects of butorphanol-oxygen anesthesia in dogs

The cardiovascular effects of two intravenous rates of butorphanol infusion (0.1 and 0.2 mg/kg/min) were measured in 32 dogs breathing oxygen and nitrous oxide in oxygen. Sixteen dogs were premedicated with atropine and the other 16 were unpremedicated. Of the dogs receiving the higher dose infusion rate, 25% moved with a tail-clamp stimulus whereas 75% moved with the lower doses. Butorphanol produced significant but similar cardiovascular depression with the two rates of infusion irrespective of the presence or absence of atropine medication. Addition of nitrous oxide resulted in further cardiac depression in all groups studied. The data suggest that butorphanol is not an attractive alternative to morphine or fentanyl as a narcotic anesthetic.