[Effect of 10% hydroxyethyl starch 200/0.5 and 10% dextran 40 on the flow property and coagulation of whole blood in vivo].

In randomized order 18 hypovolemic patients undergoing minor surgery received either 500 ml of 10% dextran 40 (n = 8) or 500 ml of 10% hydroxyethylstarch 200/0.5 (n = 10) preoperatively. There were no significant changes in hemoglobin, hematocrit, colloid osmotic pressure, total serum protein, platelet count, platelet aggregation and hemostatic tests. The shear dependent viscosity of whole blood was determined at the relevant range of 1.24-91.0 s-1. Both colloids cause a marked decrease of whole blood viscosity, which is detectable at low shear rates still 24 h later. Plasma viscosity shows no changes in either group. The criteria for preferring one of the colloids for decreasing the blood viscosity will depend on the incidence and severity of undesired adverse reactions.