Blood filtration in patients with peripheral vascular disease

Abstract

Erythrocytes must undergo considerable deformation to pass through the capillaries of the microcirculation. A decrease in the deformability of these cells could be especially detrimental to the patient with peripheral vascular disease (PVD). Experiments were designed to separate the filtration abnormalities of plasma versus the red cell in PVD patients. Polycarbonate filters 25 mm in diameter with 3 or 5 micron pores and a high porosity (4 × 10⁵) were used. To study the effects of red cells without plasma, they were suspended in a sodium chloride tris buffer at a hematocrit of 0.5%. The filtrate was passed using only gravity and the results reported as the time in seconds for one milliliter to pass through the filter (FT). Forty-three PVD patients and 34 controls were studied. Suspensions of red cells in their native plasma at an hematocrit of 3.2% were studied to assess the influence of plasma factors. Matched blood types of patients and controls were also used in mixing studies on plasma and red cells. There was a small but significant increase in the FT of the PVD patient’s RBC. However, acellular plasma of these patients showed marked prolongation of filtration time which could account for all of the changes found in whole blood. In the mixing studies the PVD plasma had a prolonged FT and the plasma from the control patients had a normal FT regardless of which red cells were being studied. Although the PVD patient’s RBC may have a slightly prolonged FT, studies of acellular plasma and mixed samples demonstrate that the plasma is the main cause of the prolonged whole blood FT in the patient with PVD.