Increased rigidity of red cells in patients with Plasmodium falciparum,and its possible relation to cerebral malaria

The rheological parameters which indicated the rigidity of red cells, ie., Red cell internal viscosity (η_i) and plasma trapping were determined in patients infected with Plasmodium falciparum and were compared to that of normal subjects. Plasma trapping was determined and this value is used for packing coefficient (k). There was an increase in plasma trapping in patients which indicated an increase in rigidity of their red cells. The internal viscosity of red cells (η_i) were determined by the blood viscosity equation: η_r = (1- kCT)^−2.5 which was proposed by Dintenfass in 1968. Although blood viscosity (η_b), plasma viscosity (η_p) and relative viscosity (η_r) of the malarial patients were significantly less fuan that of nonnal subjects, the actual volume concentration of red cells (C = Hct/k) of these patients were also significantly less than that of normal subjects. And it was found that the mean Tk value of the patients was significantly higher than that of normal subjects. Since T is equal to (P + 0.4)/(p + 1), where p is η_i/η_p, then the η_i of the patients were significantly higher than that of the nolmal subjects. These findings lead us to postulate that increased rigidity of the red cells is behind the mechanism of vascular obstruction in patients with cerebral malaria.