Veno-venous Extracorporeal Membrane Oxygenation (VV-ECMO) Heparin Study

Extracorporeal membrane oxygenation (ECMO) has been increasing used over the past decade as supportive therapy in patients with respiratory failure, in order to avoid life-threatening hypoxemia, in cases otherwise refractory to conventional treatment. Veno-venous ECMO (VV ECMO) removes carbon dioxide and significantly improves oxygenation in patients with severe lung failure. System anticoagulation is provided for patients undergoing ECMO therapy to prevent clot formation in the ECMO circuit cannulas, circuit tubing, centrifugal pump, and/or oxygenator. Heparin is the standard anticoagulant for ECMO therapy. Although technological advancements and increasing clinical experience have made the use of VV ECMO safer, bleeding and thrombosis are common complications accounting for the majority of morbidity and mortality in ECMO-treated patients.The optimal anticoagulation management for patients on VV ECMO is not known. Thrombotic episodes, characterized mainly by circuit-related clotting, have become more manageable with improvements in ECMO circuit technology and heparin-coated lines. The Extracorporeal Life Support Organization (ELSO) guidelines describe bleeding as the most common complication during extracorporeal life support. Bleeding has been reported to occur in as many as 30% of patients receiving ECMO therapy, and depending on the site of the hemorrhagic complication, can be fatal. Bleeding may occur from mucous membranes, the uterus in women in childbearing years, the GI tract, or bleeding into the head or brain parenchyma. Intra-cranial hemorrhage is the most serious and usually extensive and fatal complication.Intra-cranial hemorrhage was identified in more than 40% of non-survivors treated with ECMO during the H1N1 flu outbreak of 2009. Other less serious complications associated with anticoagulation are anemia and the risks associated with transfusions. Review of our own institutional ECMO experience revealed 10 cases of VV ECMO during which anticoagulation had to be held for clinical reasons, all without subsequent increases in thrombotic complications. Identifying the safest approach to anticoagulation is essential to the future management of patients on ECMO support. In this prospective randomized clinical trial, the investigators propose to evaluate the safety and efficacy of subcutaneous heparin anticoagulation compared to the standard of care systemic intravenous anticoagulation in subjects requiring veno-venous extracorporeal membrane oxygenation for respiratory failure.