Measurements of right ventricular volumes during fluid challenge. The effects of fluid loading on RV function were studied in 41 acutely ill patients monitored with a modified pulmonary artery catheter equipped for measuring RVef. Hemodynamic evaluation was performed before and after infusion of 300 ml of 4.5 percent albumin solution in 30 min. Changes in SI did not correlate with Pra or Ppao but did with RVEDVI. For the entire group, RVef was unchanged (27 +/- 9 vs 27 +/- 9 percent). In the eight patients with an initial RVEDVI greater than 140 ml/m2, the fluid challenge increased Pra and Ppao and reduced LVSWI without any other significant effect. There was no significant correlation between RVEDVI and Pra and only a weak correlation between RVESVI and Ppa. However, there was a highly linear correlation between both RVEDVI and RVESVI and changes in RVEDVI and in RVESVI, suggesting that in the absence of severe pulmonary hypertension RV output is primarily dependent on RV preload. 