Effect of cardiac output on gas exchange in one-lung atelectasis

To evaluate the effect of administration of dobutamine on gas exchange in patients with one-lung atelectasis during pneumonectomy, ten patients with normal pulmonary function and localized carcinoma of the lung were studied during pulmonary resection. With each patient in the lateral decubitus position, hemodynamic profiles and oxygen transport data were recorded before and after administration of dobutamine at 5 micrograms/kg/min. Patients were ventilated with one-lung anesthesia and administration of 100 percent oxygen. With infusion of dobutamine, the heart rate, cardiac index, and LVSWI significantly increased. Mean arterial pressure increased while PAP fell. Systemic and pulmonary vascular resistance also declined. Arterial oxygenization and delivery improved, while oxygen uptake was unchanged. Pulmonary shunt fraction was significantly reduced. While the mechanism for shunt reduction in our patients is unclear, operative factors may include pulmonary vasodilation with dobutamine inhibition of HPV. The negative impact of reduced HPV may have been lessened by gravitational distribution of blood flow and dobutamine-mediated reduction in PAP in our patients.