Background Hydroxyethyl starch (HES) is a group of artificial colloid solutions widely used for plasma expansion and volume resuscitation. HES consist of branched chains of hydroxylated glucose molecules defined by average molecular weight, degree of hydroxyethylation, and C2/C6 ratio. Several clinical reports and in vitro experiments have documented an impaired coagulation system induced by haemodilution with HES and other colloid plasma expanders. The exact mechanisms responsible for HES induced coagulopahty are not fully understood although reduced levels of von Willebrand factor (vWF), acquired platelet dysfunction, reduced factor VIII levels, and dysfunctional fibrinogen polymerization seems to reflect an important aspect of the pathogenesis.