Effects of hydroxyethyl starches on hemostasis

SUMMARY Hydroxyethyl starch (HES) solutions are frequently used colloidal plasma expanders which are indicated to restore and maintain intravascular volume and to improve tissue perfusion. The development of HES solutions since their introduction into clinical practice has centered on designing starch molecules with an increased oncotic pressure and hemodynamic efficacy while minimizing the risk of adverse reactions such as anticoagulant effects. This article reviews specific anticoagulant side effects of various HES generations, including hetastarch, pentastarch and tetrastarch. Slowly degradable HES solutions have a more pronounced impact on coagulation than rapidly degradable HES. The decrease in factor VIII and von Willebrand factor may be due to complex binding to HES macromolecules and accelerated elimination. Extracellular coating of platelets by HES molecules results in an inhibition of platelet aggregation and adhesion. Thrombin–fibrin interaction, fibrin polymerization, activation of factor XIII, as well as clot resistance to fibrinolytic degradation is reduced in the presence of HES. Balanced salt solutions cause fewer coagulation abnormalities than HES dissolved in saline. Possible approaches to reverse HES-induced coagulopathy may include the administration of desmopressin, fibrinogen and factor XIII concentrates. Hetastarch attenuates hypercoagulability in patients at risk for thrombotic episodes and increases perioperative bleeding, while blood loss and transfusion requirements were not different in patients exposed to tetrastarch compared with gelatin or albumin. Accordingly, tetrastarch appears to be a suitable volume expander in the routine perioperative setting because of adequate volume efficacy and minimal risk for hemostatic derangements. Contraindications and maximum daily doses need to be acknowledged.