Effect of changes in the intravascular volume during hemodialysis on blood viscoelasticity

Abstract

Adoption of high rate of ultrafiltration (UF) during hemodialysis (HD) may affect the hemorhelogical blood profile, by changing Hematocrit (Hct) and the concentration of plasma proteins, which may in turn interfere with tissue perfusion. The aim of this work is to examine the effect of acute volume change during dialysis on the hemorheological variables. The study included 21 hemodialysis patients. Hematocrit (Hct) and percent decrease in blood volume (BV) were recorded by blood volume monitor. Blood samples were taken before and at the end of dialysis, for measuring plasma fibrinogen and haemorheological variables, which included blood viscosity, plasma viscosity, red cells elasticity and aggregation. The UF volume was 3.52±1.54 L. Hct increased from 34.2±6.1 to 42.1±7.3% (P<0.001), and blood volume (BV) decreased to 85.5±6.4% (P<0.001). Blood and plasma viscosity significantly increased from 3.28±0.69 to 5.48±0.85 mPa.s (P<0.001), and from 1.24 ± 0.16 to 1.65±0.24 mPa.s (P<0.001), respectively. Changes in plasma viscosity were correlated to changes in plasma fibrinogen (r=0.63, P<0.05), while the increase in blood viscosity was correlated to the percent reduction in blood volume (r=0.85, P<0.005). Red cells elasticity increased from 0.26±0.12 to 0.48±0.18 mPa.s (P<0.05), and the aggregation index rose from 0.86±0.31 to 1.25±0.26 (P<0.01). This combination of increased plasma viscosity and red cell aggregability may lower the velocity of erythrocyte transfer inside the tissue capillaries after HD, which may affect tissue perfusion. Moreover, increased elasticity may require more energy from the heart to disaggregate the cells, and this may induce problems in the patients with cardiac dysfunction. In conclusion, the hemorheological variables change after dialysis in the direction which may impede the flow inside the microvessels.