IN-VIVO EFFECTS OF PLASMA SUBSTITUTES ON THE RHEOLOGICAL PROPERTIES OF BLOOD

The objective was to investigate in vivo the rheological effects of pl asma substitutes (fluid gelatin, dextran 40, dextran 60, hydroxyethyls tarch). The study was performed during a hypervolemic hemodilution in 60 adult volunteers who underwent an odontological surgery. Two contro l groups were infused with Ringer-Lactate or 4% human albumin. Each pa tient was infused with 500 ml of plasma substitute or control fluid. B lood samples were obtained at four different times : prior to (t0) and immediately after (t1) the infusion, then 3 hours (t2) and 24 hours ( t3) after the hemodilution. At t1 and t2, plasma viscosity did not pre sent important variations, except for the group infused with dextran 6 0 where a significant increase in plasma viscosity was observed. Blood viscosity and erythrocyte aggregation measurements were performed at hematocrit 40 % to determine the intrinsic properties of substitute an d eliminate the effects of hemodilution. Blood viscosity at high shear rates underwent minor variations in all groups. In contrast, blood vi scosity at low shear rate and aggregation parameters exhibited importa nt variations which markedly depended on the used substitute. The infu sion of Ringer-Lactate, albumin and dextran 40 induced a significant d ecrease in blood viscosity and in erythrocyte aggregation. With dextra n 60 and gelatin, blood viscosity and erythrocyte aggregation increase d. Finally, the infusion with hydroxyethylstarch did not present impor tant differences as compared to the results recorded at to. Twenty for hours after the infusion, it should be noted an increase in plasma fi brinogen, probably due to surgery, which caused an increase in erythro cyte aggregation in all groups. In conclusion, in the case where a rhe ological effect is seeked, the choice of a plasma substitute has to ta ke into account the specific effects of plasma substitutes on the micr oscopic rheological properties of blood, specially aggregation. (J Mal Vasc, 1993, 18, pages 126-133).