Effects of transfusion on rheological properties of blood in sickle cell anemia.

The effects of transfusion on the rheological properties of blood in sickle cell anemia were studied in 15 patients. Blood samples were obtained before and after transfusion of normal (hemoglobin AA) packed cells. Blood viscosity was determined with a coaxial cylinder viscometer over a wide range of shear rates. The index of oxygen dependence of blood viscosity (eta O2) was calculated as the ratio of viscosity values at low PO2 (20 mm Hg) and at high PO2 (100 mm Hg) levels. After transfusion, blood viscosity significantly increased as a result of an evaluation of hematocrit. Although transfusion of normal cells into sickle cell anemia patients results in an increased oxygen content of blood and a decreased oxygen dependence of blood viscosity, an elevation of hematocrit value beyond 35 per cent may cause a high viscosity state and outweigh the benefits of transfusion. Judicious monitoring of blood viscosity should serve as a guide for blood transfusion in these patients.