Thrombosis and Bleeding in Extracorporeal Membrane Oxygenation (ECMO) Without Anticoagulation: A Systematic Review

Extracorporeal membrane oxygenation (ECMO) causes both thrombosis and bleeding. Major society guidelines recommend continuous, systemic anticoagulation to prevent thrombosis of the ECMO circuit, though this may be undesirable in those with active, or high risk of, bleeding. We aimed to systematically review thrombosis and bleeding outcomes in published cases of adults treated with ECMO without continuous systemic anticoagulation. Ovid MEDLINE, Cochrane CENTRAL and CDSR, and hand search via SCOPUS were queried. Eligible studies were independently reviewed by two blinded authors if they reported adults (≥18 years) treated with either VV- or VA-ECMO without continuous systemic anticoagulation for ≥24 hours. Patient demographics, clinical data, and specifics of ECMO technology and treatment parameters were collected. Primary outcomes of interest included incidence of bleeding, thrombosis of the ECMO circuit requiring equipment exchange, patient venous or arterial thrombosis, ability to wean off of ECMO, and mortality. Of the 443 total publications identified, 34 describing 201 patients met our inclusion criteria. Most patients were treated for either acute respiratory distress syndrome or cardiogenic shock. The median duration of anticoagulant-free ECMO was 4.75 days. ECMO circuity thrombosis and patient thrombosis occurred in 27 (13.4%) and 19 (9.5%) patients, respectively. Any bleeding and major or "severe" bleeding was reported in 66 (32.8%) and 56 (27.9%) patients, respectively. Forty patients (19%) died. While limited by primarily retrospective data and inconsistent reporting of outcomes, our systematic review of anticoagulant-free ECMO reveals an incidence of circuity and patient thrombosis comparable to patients receiving continuous systemic anticoagulation while on ECMO.