WHOLE BLOOD VISCOSITY DETERMINED BY PLASMA PROTEIN, HEMATOCRT, MEAN CORPUSCULAR VOLUME

Abstract

Therapeutic decisions in the management of neonatal hyperviscosity are often made on the basis of hematocrit (Hct) values only. However, in tubes with the diameter of arterioles, whole blood viscosity (WBV) increases also with plasma viscosity (PV), red blood cell (RBC) aggregation and impaired RBC deformability. In order to determine the correlation between total plasma protein (TPP) as a measure of PV, and Hct at various mean corpuscular volumes (MCV) on a WBV of 4.2cP previously found to be clinically significant, we adjusted the placental blood of 20 premature and 10 term infants, and the venous blood of 10 adults to a Hct between 50 and 70% and measured TPP and WBV (100μm-capillary viscometer). From these data a nomogram for WBV = 4.2cP was constructed. Thus, a plot for TPP and Hct below the appropriate MCV line indicates a WBV with a lower risk for symptomatic hyperviscosity. The regression equation expresses the critical Hct for this WBV as it is influenced by TPP and MCV. It will be noted that certain therapeutic measures e.g., transfusions with plasma, albumin, or RBC with their attendant change in TPP and MCV may alter whole blood viscosity unfavorably.