To test whether acute denervation alters the vascular effects of dopamine and dobutamine, we anesthetized 16 greyhounds and placed them on total cardiopulmonary bypass (CPB). Eight dogs received total spinal anesthesia before drug testing; eight dogs were tested in the absence of total spinal anesthesia. During dopamine and dobutamine infusions, venous capacitance [determined by the volume of the CPB venous reservoir (VR)] and mean arterial pressure (MAP) were monitored. The CPB pump flows remained constant throughout our studies. Every dog received six increasing doses of both drugs. In the absence of total spinal anesthesia, both dopamine and dobutamine increased VR (decreased venous capacitance) in a dose-dependent manner. Do but amine decreased MAP in a dose-related fashion but do pa mine had no significant effect on MAP. After total spinal anesthesia, both dopamine and do but amine produced greater dose-related increases in VR (i.e., decreases in venous capacitance) than in the absence of spinal anesthesia. Dopamine increased MAP but dobutamine had no significant effect. These data demonstrate how dopamine and dobutamine differ in their effects on the arterial circulation in the presence or absence of spinal anesthesia. The acute denervation of spinal anesthesia altered venous and arterial dose-response relationships of both drugs. Finally, our study demonstrates the effectiveness of dobutamine and, perhaps even more so, dopamine as possible alternatives to ephedrine for the pharmacologie correction of the non cardiac circulatory se quelae of spinal anesthesia.
(C) 1987 International Anesthesia Research Society