Catecholamine infusion in vagotomized dogs during thiamylal-halothane and pentobarbital anesthesia.

The cardiac arrhythmogenic infusion rate of epinephrine, dopamine, and dobutamine in vagotomized dogs was determined during thiamylal-halothane and pentobarbital anesthesia. Epinephrine, dopamine, and dobutamine were administered until 4 or more ventricular arrhythmias on duplicated trials were produced or until a predetermined maximum infusion rate was attained. The mean ventricular arrhythmogenic infusion rates (micrograms X kg-1 X min-1) during thiamylal-halothane anesthesia were: epinephrine, 0.57 +/- 0.24; dopamine, 23.7 +/- 8.26; and dobutamine, 10.21 +/- 3.54. Few arrhythmias were produced at the maximum administered infusion rate during pentobarbital anesthesia (2 of 6 with epinephrine, 3 of 6 with dopamine, and 0 of 6 administered dobutamine). Heart rate and blood pressure increased progressively with increasing infusion rates for all 3 catecholamines during thiamylal-halothane anesthesia. Heart rate and blood pressure changes were similar during pentobarbital anesthesia except for blood pressure changes during dobutamine infusion.