Primary hemostasis in hemodilution--1) Hematocrit.

There are still controversies about the influence of acute preoperative hemodilution on coagulation. Therefore, we examined the platelet function by the In-vitro bleeding test (IVBT) using composed blood samples of different hematocrit but constant platelet concentration. We found an inverse correlation between hematocrit and bleeding time (p less than .05), volume (p less than .001) and flow (p less than .001). These data suggest a considerable impairment of primary hemostasis, due to low hematocrit. The cause may be an alteration of the hemorheology as well as the interaction between red cells and platelets themselves.