Concordance and discordance of anticoagulation assays in children supported by ECMO: The truth is out there

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Introduction Extracorporeal membrane oxygenation (ECMO) provides critical support to patients in severe cardiac and respiratory failure, but it requires anticoagulation to prevent complications like bleeding and thrombosis. Heparin, the primary anticoagulant utilized, is monitored by activated partial thromboplastin time (aPTT) and anti-Factor Xa (AntiXa) levels. Discordance between the two assays complicates its titration and the impact on patient outcomes is not well-established. This study examines the prevalence of discordance, its impact on heparin dosing, and the association of bleeding, thrombosis, ICU-free days, and mortality in pediatric ECMO patients. Methods This secondary analysis of the Bleeding and Thrombosis on Extracorporeal Membrane Oxygenation study consisted of 511 patients under 19 years. Demographics, laboratory results, ECMO indications, daily heparin doses, and clinical outcomes were collected. Discordance was categorized as major or minor, and adjustments to heparin dosing were analyzed for appropriateness based on normal ranges of aPTT and AntiXa. Logistic regression models assessed the impact of heparin titration strategies on bleeding, clotting, ICU-free days, and mortality. Results Major discordance occurred on 17.5% of days with high aPTT and low AntiXa being most common. Titrating heparin based on AntiXa in scenarios of discordance was associated with an 11% lower incidence of bleeding compared to aPTT ( p = .02). Higher proportion of concordance was independently associated with increased bleeding and/or clotting, but not significantly affect ICU-free days or mortality. Conclusion Discordance is common in pediatric ECMO patients. AntiXa-guided heparin titration, notably during discordant periods, is associated with fewer bleeding and clotting events. This emphasizes the need for improved anticoagulation protocols since discordance does not demonstrate worse ICU-free days or mortality.