Prospective Randomized Study Of Anticoagulation Monitoring With Thromboelastography Versus aPTT During Extracorporeal Membrane Oxygenation In Adults

Extracorporeal membrane oxygenation (ECMO) is frequently used as a supportive tool in the settings of acute severe respiratory and/or circulatory failure. The presence of the extracorporeal circuit and oxygenator bring along the need to anticoagulate the patients in order to prevent activation of the coagulation cascade that can lead to thrombosis of the artificial surfaces and losses of coagulation factors, fibrinogen and platelets. Despite tight monitoring with different anticoagulation essays bleeding remain the main threat for the patients on ECMO, leaving thrombosis as an anecdotic event.

In our institution, anticoagulation during ECMO is monitored mainly with aPTT ratio in a range of 1.5 to 2 (patient to normal). Recently, the investigators started to match Thromboelastography (TEG) assays to activated Partial Thromboplastin Time (aPTT) and Activated Clotting Time (ACT) routine measurements during ECMO. Data from a preliminary analysis of thirty-two patients show that in nearly half of TEG assays, the R (reaction time) parameter which is sensitive to inhibition of fibrin formation by heparin, was consistently prolonged despite aPTT and ACT were in the normal range. In the same patients the investigators registered high rate of bleeding (nearly 40% of patients suffered from clinically significant bleeding, i.e. bleeding that required heparin dose reduction, blood transfusions or interruption of the extracorporeal support). These findings suggests the possibility that the actual target of aPTT ratio might be overrated.

The purpose of this study is to test safety and feasibility of standardized protocol based on TEG versus current practice (aPTT) to manage anticoagulation during ECMO.

40 consecutive adults patients undergoing ECMO will be randomized in either the TEG-driven anticoagulation group or the aPTT-driven group. Written informed consent will be obtained according to national legislation.

In both groups, when the patient is connected to ECMO, an heparin bolus of 50-70 UI/kg (depending on baseline aPTT value) will be administered followed by a continuous infusion of 18 UI/kg/h started; for the first 12 hours thereafter proper anticoagulation level will be monitored with Activated Clotting Time (ACT, therapeutic range 180-210 seconds, performed every 1 or 2 hours according to the standardized protocol). From the thirteenth hour onwards each group will follow either aPTT monitoring or TEG according to randomization. Every morning in both groups aPTT, TEG, Antithrombin and anti-Factor Xa activity will be assessed.