COMPARATIVE EFFECTS OF DOPAMINE AND NOREPINEPHRINE ON MYOCARDIAL FUNCTION AND METABOLISM DURING EXPERIMENTAL CARDIOGENIC SHOCK

¹ Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina

After anesthesia, cardiogenic shock was produced in 38 open-chest dogs by coronary embolization with plastic microspheres (300-350µ The shock state was characterized by marked reductions (35-60%) in aortic pressure, total aortic and coronary flows (electromagnetic flowmeters), stroke volume and myocardial contractile force (strain-gauge arch). There was also evidence of myocardial hypoxia as manifested by reductions in myocardial O₂ consumption and lactate extraction ratios. After a shock period of 15 to 30 minutes duration, 15 of the animals were infused with dopamine, 14 with norepinephrine and 9 with saline. The infusions were scheduled for 60 minutes with hemodynamic and metabolic data taken at 30-minute intervals. Of the 9 animals receiving saline, only 3 survived the 60-minute infusion period, whereas 11 of 15 receiving dopamine and 12 of 14 receiving norepinephrine survived. Both dopamine and norepinephrine infusions resulted in significant improvement in all depressed parameters studied, and in general, these increments were of equal magnitude. On the other hand, the surviving saline-treated animals remained in shock and showed little evidence of improvement. It is concluded that in many respects dopamine is similar to norepinephrine in its ability to restore the cardiovascular function after coronary embolization.