Effects on right ventricular function of a change from dopamine to dobutamine in critically ill patients

In 15 critically ill patients requiring adrenergic support, right ventricular ejection fraction (RVEF) and right ventricular (RV) volumes were measured by the thermodilution technique receiving 5 micrograms/kg.min of dopamine and after replacement by the same dose of dobutamine. Shift from dopamine to dobutamine resulted in significant increases in stroke index from 28.1 +/- 3.6 to 31.0 +/- 3.8 ml/m2 (p less than .01) and significant decreases in pulmonary artery balloon-occluded pressure from 15.1 +/- 1.0 to 13.9 +/- 1.2 mm Hg (p less than .05) and right atrial pressure (RAP) from 14.0 +/- 1.3 to 12.2 +/- 1.1 mm Hg (p less than .05). RVEF increased slightly but significantly from 21.5 +/- 2.7% to 23.7 +/- 2.9% (p less than .01) so that RV end-diastolic volume (RVEDVI) was unchanged (140 +/- 12 vs. 141 +/- 12 ml, nonsignificant). RVEDVI/RAP ratio increased from 11.3 +/- 1.0 to 12.9 +/- 1.1 ml/mm Hg (p = .037). These results support the view that dobutamine has more favorable effects on RV function than dopamine in critically ill patients in the absence of profound hypotension and also indicates that higher filling pressures under dopamine administration can be related to changes in ventricular pressure/volume relationship.