Antithrombin during veno-venous extracorporeal membrane oxygenation with heparin anticoagulation: A single-center cohort study

Introduction: Antithrombin (AT) is a natural anticoagulant essential to enhancing the unfractionated heparin (UFH) anticoagulant effect. Its supplementation in the management of UFH-based anticoagulation during veno-venous extracorporeal membrane oxygenation (VV ECMO) has a strong pathophysiological rationale. Methods: This is a single-center, retrospective cohort study of adult VV ECMO patients with anticoagulation maintained by UFH targeting an activated partial thromboplastin time (aPTT) of 40–50 s and AT activity >80%. We compare anticoagulation management and survival outcomes between AT subpopulations, defined by a threshold AT activity ≥80%. Linear and logistic regression analyses were used to evaluate the variation in AT activity and its association with ICU survival. Results: In 244 patients enrolled from 2009 to 2022, anticoagulation was maintained by a median heparin dose of 11.4 IU/kg/h [IQR: 8.2–14.7] with a mean aPTT of 46.1 s (±7.3) and AT activity of 88.9% (±17.0). A lower mean aPTT, higher dose of UFH and shorter fraction of time without UFH were associated with higher AT activity (p <.01). Higher AT activity showed a consistent association with ICU survival (for 10% increase of AT, odds ratio for ICU mortality: 0.95; 95% CI 0.93–0.97; p value <.01). Conclusions: There is a positive association between AT activity and UFH requirements but no significant difference in the rate of bleeding events. A higher mean AT during VV ECMO was associated with ICU survival. Future studies are needed to differentiate between exogenously supplemented versus endogenous AT effect.