The Hemodynamic Response to Dopamine and Nitroprusside Following Right Atrium–Pulmonary Artery Bypass (Fontan Procedure)

Abstract

Cardiac output is critically dependent upon pulmonary vascular resistance after right atrium-pulmonary artery bypass (Fontan procedure), since there is no pulmonary ventricle in the circulation. Inotropic agents, including dopamine, may increase pulmonary vascular resistance and, therefore, might have an adverse effect on cardiac output. The present study determined the hemodynamic responses to dopamine and nitroprusside of 9 patients following right atrium–pulmonary artery bypass. Particular attention was given to effects on cardiac output (CI), pulmonary vascular resistance, and right atrial pressure (RAP). Baseline hemodynamic data were measured without drugs, with dopamine at 7.5 μg/kg/min, with sodium nitroprusside up to 5.0 μg/kg/min, and with a combination of dopamine, 7.5 μg/kg/min, and sodium nitroprusside, 1.0 7.5 μg/kg/min. Right and left atrial pressures (LAP), mean arterial blood pressure ▪, heart rate (HR), and CI were measured. Stroke volume index and pulmonary arteriolar resistance index were calculated. The increase in CI from baseline (1.98 ± 0.86 liters per minute) was significant for infusions of dopamine (2.75 ± 1.05, p < 0.001), sodium nitroprusside (2.57 ± 0.78, p < 0.001), and both drugs (2.74 ± 0.84, p < 0.001). The increased CI was achieved primarily by a significant increase in HR with dopamine and by an increase in stroke volume index with sodium nitroprusside. With a similar increment in CI, the RAP was significantly decreased from baseline (21 ± 4 torr) with sodium nitroprusside (15 ± 3, p < 0.001) but was unchanged with dopamine. Pulmonary arteriolar resistance index decreased significantly from baseline (375 ± 230 dynes sec cm −5/m 2) with sodium nitroprusside (169 ± 132, p < 0.001), and, interestingly, with dopamine as well (273 ± 165, p < 0.05). Both dopamine and sodium nitroprusside in these dosages have favorable effects on CI and pulmonary arteriolar resistance index in patients after right atrium-pulmonary artery bypass. Whenever feasible, sodium nitroprusside is preferred for increasing CI after such a bypass procedure, since lower RAP decreases the severity of fluid retention, ascites, and chest tube drainage.