A Comparison of Estimation of Blood Volume by Hematocrit Dilution with Prediction of Blood Volume by Patient Morphology

Abstract

Determination of circulating blood volume (CBV) is useful for quantifying and managing several physiologic parameters in patients undergoing cardiopulmonary bypass (CPB). Blood was drawn and the hematocrit (HCT) measured immediately pre and five minutes post initiation of CPB, in adult cardiac surgery patients (n=67). The CBV was estimated by HCT dilution, and compared utilizing regression analysis and Student's t-test, with eight formulas for predicting CBV from patient morphology. CBV by HCT dilution vs Patient Morphology (T-Test) P value 1) ml/kg 65ml/kg <.0001 2) Allen-men Height3* Body mass (H*TBM) .0001 3) Allen-wmn Height3* Body mass (H*TBM) <.0001 4) Baker 2.68L/m2 <.0001 5) Nadler1-men Regression of Baker <.0001 6) Nadler1-wmn Regression of Baker .0001 7) Nadler2-men Regression of Allen-men <.0001 8) Nadler2-wmn Regression of Allen-wmn .0002 There is a significant statistical difference between CBV estimated by HCT dilution and CBV predicted by patient morphology. None of the equations investigated are adequate predictors of CBV estimated by HCT dilution in patients undergoing CPB.