Hematological and Rheological Aspects of Oxygen Transport: The Optimal Hematocrit

Abstract

The development in recent years of clinical hemorheology as a subspeciality has been an important, possible overdue, event. However, as with any new discipline the originators, and recent converts, tend to overemphasize the importance of their area of interest to the detriment of interrelationships with other disciplines. The oxygen transport chain is a classical example where scientific reductionism has broken a complex and integrated system into its individual components, losing sight of the fact that the whole oxygen transport chain is greater than the sum of its parts. The apparent viscosity of blood is largely determined by the hematocrit with red cell deformability, plasma proteins and red cell and plasma protein interaction being of lesser importance. Although leukocytes and platelets may have a marked affect on microcirculatory flow, they have little effect on whole blood viscosity and the pathophysiological aspects are mainly due to activation within the microcirculation [1].