The pulmonary and systemic circulatory response to dopamine infusion.

1. The pulmonary and systemic circulatory responses to dopamine infused at 8, 15, 25 and 30 mug/kg per min were studied in eight mongrel dogs.2. Mean pulmonary artery pressure, mean left atrial pressure, mean aortic pressure, mean aortic flow and the electrocardiogram were monitored in openchest preparations. Pulmonary vascular resistance, systemic vascular resistance and stroke volume were calculated.3. Significant increases in mean pulmonary and aortic pressures were noted at dopamine infusions of 25 and 30 mug/kg per min. The left atrial pressure fell significantly at 15 mug/kg per min and rose significantly at 30 mug/kg per min. Mean aortic flow increased at all four doses, while heart rate showed no change. Pulmonary vascular resistance did not change significantly at any dose level, but systemic vascular resistance fell slightly at 8 and 15 mug/kg per min and rose significantly at 30 mug/kg per min. Stroke volume was significantly elevated at infusions of 25 and 30 mug/kg per min.4. The systemic circulatory response to dopamine is similar to that described by previous investigators.5. The increased pulmonary pressures without change in resistance suggest a dopamine-induced increase in smooth muscle tension in the pulmonary vasculature.