Abstract Body (Do not enter title and authors here):
Introduction: Systemic anticoagulation in Extracorporeal Membrane Oxygenation (ECMO) aims to reduce the risk of patient and circuit thrombosis, but requires monitoring due to risk of bleeding. Activated partial thromboplastin time (aPTT) is one of many tests utilized for this purpose. However, it lacks validation in ECMO patients and its clinical utility necessitates further analysis.

Aim: We aim to elucidate associations between low versus high aPTT-guided anticoagulation monitoring and total time, survival, bleeding, and thrombotic events during ECMO.

Methods: A retrospective review was conducted on 93 patients requiring ECMO at our institution between January 2020 and March 2021. Study inclusion required more than 2 days on ECMO and maintenance on anticoagulation with aPTT targets predominantly greater (>) or less than (<) 60 seconds (s). Final cohort was 74 subjects; 30 subjects with majority aPTT targets <60s composed the control “low” aPTT group and 44 subjects with aPTT targets >60s composed the “high” aPTT group. Primary outcomes were survival to decannulation, survival to discharge, average time on ECMO, and incidence of bleeding and thrombotic events during ECMO. Bleeding and thrombotic events were classified into subtypes and incidence of each was recorded. Statistical analyses were performed with Fisher’s exact, Pearson’s chi-square, and Student’s t-tests with an alpha level of .05 on IBM SPSS software.

Results: The high group required a longer average time on ECMO (29.5 days versus 14.3 days; p = .002; 95% CI [5.5; 24.7]). Chi-square tests did not show an association between the low versus high groups and survival to decannulation (22/30 and 35/44; p = .533), survival to hospital discharge (17/30 and 30/44; p = .312), or overall incidence of bleeding (18/30 and 20/44; p = .219) and thrombotic events (7/30 and 14/44; p = .427). Regarding subtypes of events, Fisher’s exact test showed an association between aPTT target >60s and severe epistaxis (1/30 in the low and 9/44 in the high group; two-tailed p = .042). Though not significant, a greater incidence of oxygenator failure and circuit thrombosis was recorded in the high group.

Conclusions: Our findings did not establish a relationship between aPTT target <60s or >60s and survival, bleeding, or thrombotic events. However, aPTT target >60s was associated with longer average ECMO time and severe epistaxis. Further investigation of aPTT-guided anticoagulation monitoring in ECMO patients is needed.