Calculated Estimates of Plasma Volume in Patients With Chronic Heart Failure-Comparison With Measured Volumes

Background: Calculated estimates of plasma volume (PV) have been developed with the use of hemoglobin/hematocrit-body weight-based methods. The accuracy of such formula-derived values has not been thoroughly evaluated. The objective of this analysis was to compare the calculated estimate and a quantitative measure of PV in patients with chronic heart failure (HF). Methods and Results: PV was measured with the use of a standardized computer-based indicator-dilution-labeled albumin technique in 110 patients with clinically stable chronic HF and correlated with paired Kaplan-Hakim (K-H) and Strauss formula estimates of PV. The K-H formula underestimated (3.4 +/- 0.7 L) and the Strauss formula overestimated (5.3 +/- 1.5 L) PV relative to the measured volume (4.3 +/- 1.1 L). Calculated PV was only moderately correlated with measured PV by the K-H formula (r = 0.64; P < .001) and weakly by the Strauss formula (r = 0.285; P = .003). Strauss formula estimates of change (%) in PV were also poorly correlated with paired measured changes in PV (r = 0.162; P = .999; n = 40). Conclusions: Calculated estimates of PV demonstrate limited association with measured volumes. These findings indicate that although formula-based estimates of PV have been shown to have prognostic value, they are limited in their reliability for volume management in patients with chronic HF.