as plasma expanders or acidosis while the effects of these agents are hardly identified by plasma based laboratory tests. TEM-guided transfusion of blood products or factor concentrates in cardiac, hepatic and major orthopedic surgery is the main application of the method. Moreover, it is successfully used in the complex situation of (poly)trauma, or in decision making for of alternative therapy such as antifibrinolytic drug administration . The clinical benefits of TEM have resulted in major savings and publications recommend that viscoelastic methods such as TEM should be used in surgical procedures where major blood loss followed by the need for transfusions can be expected. Limitations of TEM Like any other haemostasis evaluating method, TEM (and thrombelastography) have limitations which need to be considered when interpreting the results. The typical assays are not responsive for the effect of von Willebrand factor or platelet antagonists such as aspirin or thienopyridines (e.g. clopidogrel), and only supratherapeutic doses of GPIIb/IIIa antagonists may influence results. The sensitivity for coagulation factor deficiencies, including those induced by oral anticoagulation, is less pronounced as compared to clotting assays. Therefore, TEM is not meant to replace laboratory assays such as prothrombin time (PT) or factor assays. However, due to the rapid availability of differential diagnostic information, TEM has become an established method in surgical procedures where blood losses can be expected. References Blood tests