Plasma protective effect on red blood cells exposed to mechanical stress

Hemodilution with plasma expanders is a widely applied practice during extracorporeal circulation and hemodialysis. Despite the immediate beneficial effects of hemodilution, such as reduction of blood viscosity and red blood cell (RBC) aggregation, elevation of blood flow in the microcirculation, etc., the dilution of plasma may cause some unfavorable effects on RBCs, amplifying the mechanical damage caused by circulatory assist devices. The authors investigated the effect of partial and total replacement of plasma on susceptibility of human and bovine RBCs to mechanical stress in vitro. Hemolysis was measured after the exposure of RBCs suspended in different media to similar mechanical stress. Experiments were performed at room temperature with control of osmolality and viscosity of the suspension media. The lowest hemolysis was obtained for RBCs suspended in serum, plasma, and albumin solutions. Hemolysis in PBS and Dextran suspensions was more than three times higher than that in plasma (p < 0.001). The protective effect depended upon protein concentration. Human RBCs were found to be significantly more sensitive to mechanical stress than bovine RBCs in all investigated suspension media (p < 0.005). Human RBCs from men suspended in plasma were found to be significantly (p < 0.05) more fragile than RBCs from women. The presence of even small amounts of plasma (such as 25%) in the suspension media significantly (p < 0.001) decreased hemolysis. However, a 30% replacement of plasma with PBS or Dextran solutions caused a statistically significant (p < 0.001) increase in mechanical hemolysis. This suggests that a decrease in the concentration of plasma proteins due to hemodilution may elevate blood damage during extracorporeal circulation and hemodialysis.