Accuracy of carboxyhemoglobin dilution method for the measurement of circulating blood volume

Abstract

Purpose: The management of circulating blood volume (BVc) is crucial in intensive care unit (ICU) patients. The purpose of this study was to verify the accuracy and precision of the carbon monoxide-labeled hemoglobin (CO-Hb) dilution method (CO method) by comparing it with the 51Cr-labeled erythrocyte dilution method (51Cr method) for the measurement of BVc. Methods: A prospective study was performed in 18 patients who underwent coronary artery bypass grafting (CABG) under mild hypothermic cardiopulmonary bypass (CPB). The BVc was measured by both the CO method and the 51Cr method at 24 hr after ICU admission in order to verify the accuracy and precision of the CO method. Paired data were assessed in absolute terms, and percentage errors were calculated by the degree of agreement. Results: Small mean differences and standard deviations between the CO method and the 51Cr method (-70.2 ± 184.8 mL) and small percentage errors (-0.49 ± 1.29%) indicated the accuracy and precision of the CO method, and a close correlation was observed (r=0.97). Conclusion: The CO method can measure BVc with a similar degree of accuracy as the 51Cr method. It is simple, repeatable and safe without the risk of exposure to radioactivity in the ICU.