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

Abstract

The rheological parameters which indicated the rigidity of red cells, ie., Red cell internal viscosity (ηi) 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 (ηi) were determined by the blood viscosity equation: ηr = (1- kCT)−2.5 which was proposed by Dintenfass in 1968. Although blood viscosity (ηb), plasma viscosity (ηp) and relative viscosity (ηr) 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 ηi/ηp, then the ηi 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. © 1995 Elsevier Science Ltd.