Basic concepts of hemorheology in microvascular hemodynamics.

Blood rheology, or hemorheology, involves the flow and deformation behavior of blood and its formed elements (ie, erythrocytes, leukocytes, platelets). The adequacy of blood flow to meet metabolic demands through large circulatory vessels depends highly on vascular control mechanisms. However, the extent to which rheologic properties of blood contribute to vascular flow resistance, particularly in the microcirculation, is becoming more appreciated. Current evidence suggests that microvascular blood flow is determined by local vessel resistance and hemorheologic factors such as blood viscosity, erythrocyte deformability, and erythrocyte aggregation. Such knowledge will aid clinicians caring for patients with hemodynamic alterations.