Patients supported with
extracorporeal membrane oxygenation (ECMO) experience a very high frequency of
bleeding and ischaemic complications, including
stroke and systemic
embolism. These patients require systemic anticoagulation, mainly with
unfractionated heparin (UFH) to prevent clotting of the circuit and reduce the risk of arterial or
venous thrombosis. Monitoring of UFH can be very challenging. While most centres routinely monitor the activated clotting time and activated partial thromboplastin time (aPTT) to assess UFH, measurement of anti-
factor Xa (anti-Xa) level best correlates with
heparin dose, and appears to be predictive of circuit
thrombosis, although aPTT may be a better predictor of
bleeding. Although monitoring of prothrombin time, platelet count and
fibrinogen is routinely undertaken to assess haemostasis, there is no clear guidance available regarding the optimal test.Additional tests, including
antithrombin level and thromboelastography, can be used for risk stratification of patients to try and predict the risks of
thrombosis and
bleeding. Each has their specific role, strengths and limitations. Increased
thrombin generation may have a role in predicting
thrombosis. Acquired von Willebrand syndrome is frequent with ECMO, contributing to
bleeding risk and can be detected by assessing the
von Willebrand factor activity-to-
antigen ratio, while the platelet function analyser can be used in urgent situations to detect this, with a high negative predictive value. Tests of platelet aggregation can aid in the prediction of
bleeding.To personalise management, a selection of complementary tests to collectively assess
heparin-effect, coagulation, platelet function and platelet aggregation is proposed, to optimise clinical outcomes in these high-risk patients.