End-diastolic volume. A better indicator of preload in the critically ill.

The relative value of pulmonary artery wedge pressure (PAWP) and right ventricular end-diastolic volume index (RVEDVI) as a reflection of the preload status of the critically ill was determined in 29 patients. Regression analysis of 131 hemodynamic studies demonstrated that cardiac index (CI) correlated better with RVEDVI (r = .61) than did PAWP (r = .42). Comparisons of PAWP and RVEDVI showed that possible misleading information concerning filling volume was provided by the PAWP at some time in 15 (52%) of these patients. In 15 patients given 22 fluid challenges, patients with a high PAWP (greater than or equal to 18 mm Hg) "responded" with a rise in CI more frequently than did patients with a low PAWP (less than 12 mm Hg). However, all eight patients with a RVEDVI less than 90 mL/m2 responded with a rise in CI, but all seven patients with a RVEDVI greater than or equal to 139 mL/m2 failed to respond. Thus, RVEDVI more accurately predicted preload recruitable increases in cardiac output.