Nonspecific rheological abnormalities in sickle cell disease.

The rheology of blood from normal healthy subjects, from sickle cell patients and hybrid red cell suspensions prepared by mixing HbSS cells with normal plasma and HbA cells with plasma of sickle cell patients were studied. The microrheological behavior was observed in a rheoscope, in which the kinetics of red cell aggregation were also studied systematically. The viscosities of plasma, sera and whole blood samples were determined in a coaxial cylinder and a cone-plate viscometer. The data show that in sickle cell disease a number of nonspecific factors capable of interfering with blood fluidity are changed. These include an elevation of the tendency to red cell aggregation (which also persists after the removal of plasma fibrinogen), the enhanced tendency to red cell aggregation (measured photometrically and by extrapolation of the viscometric data plotted according to the Casson equation) and consequently strong decrease in apparent fluidity, especially at low shear rates. These unspecific abnormalities persist even after deoxygenation and complicate the specific effect of HbSS cells following hemoglobin gelation. Comprehensive pathophysiological hypothesis about circulatory disturbances in sickle cell patients is given which includes concepts about the interaction of general and local hemodynamics and of specific and nonspecific hemorheological determinants of apparent blood fluidity.