LAUSR

BACKGROUND AND PURPOSE There remains a paucity of literature regarding best practice for antithrombin (AT) monitoring, dosing, and dose-response in pediatric ECMO patients. EXPERIMENTAL APPROACH We conducted a retrospective cohort study at a quaternary care pediatric intensive care unit in all patients <18 years of age supported on ECMO from June 1, 2011 to April 30, 2020. Adverse events and outcomes were characterized for all ECMO runs. AT activity and replacement were characterized and compared between two clinical protocols. AT activities measured post- vs pre-AT replacement were compared to characterize a dose-response relationship. KEY RESULTS The final cohort included 191 patients with 201 ECMO runs and 2,028 AT activity measurements. The median AT activity was 65% (interquartile range [IQR], 51-82) and 879 (43.3%) measurements met the criteria of deficient. The overall median AT dose and increase in AT activity were 50.6 units/kg/dose (IQR, 39.5-67.2) and 23.5% (IQR, 9.8-36.0), respectively. In the protocol that restricted AT activity measurements to clinical scenarios concerning for heparin resistance, there was significantly higher dosing in conjunction with significantly less overall administrations. Approximately one third of AT activity remained deficient after repletion. There was no difference in mechanical complications, reasons for discontinuation of ECMO support, time on ECMO, or survival between protocols. CONCLUSION AND IMPLICATIONS There was a high prevalence of AT deficiency in pediatric ECMO patients. An AT replacement protocol based on evaluating heparin-resistance is associated with less AT administration, with similar circuit and patient outcomes. Further data are needed to identify optimal dosing strategies.