Cardiac surgical patients frequently require catecholamines, typically administered via the central venous circulation. Potential disadvantages of this route of administration include catecholamine metabolism by the pulmonary vascular bed before gaining access to the heart and pulmonary vasoconstriction producing increased pulmonary vascular resistance. We therefore prospectively compared administration of epinephrine via the left atrium versus central venous administration of epinephrine with particular interest in cardiac output, mean pulmonary artery pressure, and pulmonary vascular resistance. Fifteen consecutive aortocoronary bypass patients were studied after cardiopulmonary bypass. Epinephrine (mean dose, 0.07 +/- 0.02 micrograms.kg-1.min-1) was administered via the central venous route, then via the left atrium, then via the central venous route again. Hemodynamic data were collected 10 minutes after changing the route of administration. Left atrial administration of epinephrine produced a 35% greater cardiac output, 25% lower pulmonary artery pressure, and 32% lower pulmonary vascular resistance when compared with central venous administration (all significant; p < 0.05). Left atrial epinephrine administration may offer hemodynamic advantage in cardiac surgical patients in whom central venous administration does not produce an adequate cardiac output or in patients with pulmonary hypertension to avoid any further increase in pulmonary vascular resistance.