IN-VIVO INVESTIGATION INTO THE EFFECTS OF HEMODILUTION WITH HYDROXYETHYL STARCH (200 0.5) AND NORMAL SALINE ON COAGULATION/

We have investigated the effects of haemodilution with either saline o r hydroxyethyl starch (200/0.5) (HES) on blood coagulation in healthy volunteers in vivo. Standard haematological tests (packed cell volume (PCV), platelets, prothrombin time (PT), activated partial thromboplas tin time (aPTT), fibrinogen, antithrombin ill, bleeding time and plate let aggregation), and thrombelastography (TEG) were performed before a nd after administration of either 0.9% saline 1000 ml or HES 1000 ml i .v. over a 30-min period. Dilution of PCV and platelet concentrations as a result of volume load were 9% in the saline group and 19% in the HES group. Reductions in fibrinogen (18.6% and 28.8%) and antithrombin III (25.5% and 37.8%) were significantly greater than could be explai ned by haemodilution alone in both groups. Indices of platelet aggrega tion were significantly enhanced by saline haemodilution, but not by H ES, which inhibited epinephrine-induced aggregation and prolonged blee ding time. TEG in the saline group showed significantly shortened r an d k times (24% and 26%, respectively), and increased alpha angle (24%) and maximum amplitude (MA, 6%). HES haemodilution decreased MA (11%) but did not affect other TEG variables. We conclude that haemodilution of normal blood exerted a procoagulant effect, possibly by enhancemen t of thrombin formation. Circulating concentrations of antithrombin II I were depleted more than could be explained by haemodilution alone, l eading to a hypercoagulable state. This effect was offset by an antipl atelet action of HES, which was not seen with saline. The mechanism is unknown.