Effects of dopamine and dobutamine on the myocardial and systemic circulation during and following cardiopulmonary bypass in dogs.

The effect of dopamine (Dp) and dobutamine (Db) on myocardial and systemic blood flow (BF) distribution was compared in dogs being weaned from cardiopulmonary bypass (CPB) after 20 min of normothermic global myocardial ischemia. Drug infusions (10 mcg/kg/min) were begun and BF was measured (radiolabeled microspheres) prior to weaning and 60 min off CPB. On CPB: Pump flows, by design, were similar (100 ml/kg/min) in Dp, Db, and saline control (NS) dogs. Dp and Db significantly (p less than 0.05) increased myocardial BF. Dp did not alter renal, visceral, and skeletal muscle BF and only increased BF to the cervical spinal cord and medulla. Db, however, significantly reduced renal (-49%), splenci (-58%), pancreatic (-27%), and colonic (-47%) BF but increased perfusion in essentially all of the central nervous system. Off CPB: Cardiac output during Dp and Db infusions was significantly greater than NS dogs (107 +/- 7 vs 152 +/- 12 vs 82 +/- 10 ml/kg/min resp.); the greater increase for Db resulting from a larger stroke volume. Dp and Db significantly increased myocardial BF. Dp increased splenic (+77%), gastric (+139%), and gallbladder (+125%) BF but had no effect on renal, hepatic, skeletal muscle, and intestinal BF. Db infusion maintained renal BF similar to NS and elevated BF to most visceral organs. The results of this study show that the myocardium responded to inotropic stimulation despite the previous ischemic insult but the BF changes varied among regional vascular beds with Dp and Db infusions during and following CPB. Of the 2 drugs, Db showed the greater inotropic response off CPB, a similar increase in myocardial perfusion and greater visceral organ bloodflow.