Sickle cell anemia as a rheologic disease.

Sickle cell anemia represents an aberration of blood rheology due to a loss of normal red cell deformability. The characteristically low hematocrit compensates for the stiffness of the sickle cells, leaving the patient with approximately normal whole blood viscosity. However, the microvascular flow of sickle cell blood is constantly jeopardized by hemoglobin gellation due to hypoxemia. The cells containing the highest concentration of hemoglobin S are the most viscous and are at the greatest risk for abrupt sickling. Successful treatment of this disease will require interruption of the basic pathogenetic mechanisms and preservation of normal blood rheology.