Original Article

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

Program in ECT, Clinical Services Department, College of Health Professions, The Medical University of South Carolina, Charleston, South Carolina

^* Address correspondence to: Jeffrey R. Acsell, BS, Medical University of South Carolina, CHP, ECT, 101 Doughty, Second Floor, Charleston, South Carolina 29401

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.