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 be neficial 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 unfavora ble effects on RBCs, amplifying the mechanical damage caused by circul atory assist devices. The authors investigated the effect of partial a nd total replacement of plasma on susceptibility of human and bovine R BCs to mechanical stress in vitro. Hemolysis was measured after the ex posure of RBCs suspended in different media to similar mechanical stre ss. Experiments were performed at room temperature with control of osm olality and viscosity of the suspension media. The lowest hemolysis wa s obtained for RBCs suspended in serum, plasma, and albumin solutions. Hemolysis in PBS and Dextran suspensions was more than three times hi gher than that in plasma (p < 0.001). The protective effect depended u pon protein concentration. Human RBCs were found to be significantly m ore sensitive to mechanical stress than bovine RBCs in all investigate d suspension media (p < 0.005). Human RBCs from men suspended in plasm a were found to be significantly (p < 0.05) more fragile than RBCs fro m women. The presence of even small amounts of plasma (such as 25%) in the suspension media significantly (p < 0.001) decreased hemolysis. H owever, a 30% replacement of plasma with PBS or Dextran solutions caus ed a statistically significant (p < 0.001) increase in mechanical hemo lysis. This suggests that a decrease in the concentration of plasma pr oteins due to hemodilution may elevate blood damage during extracorpor eal circulation and hemodialysis.