(519) Correlating ROTEM CT to Standard Coagulation Tests for Pediatric ECMO Patients

Introduction: Standard of care laboratory tests that monitor anticoagulation during extracorporeal membrane oxygenation (ECMO) often have variable correlation to each other and to anticoagulant dosing. Viscoelastic tests, specifically rotational thromboelastometry (ROTEM), may have improved correlation but have limited data in pediatric ECMO population. The objective of this study is to correlate extrinsic (EXTEM) and intrinsic (INTEM) ROTEM clotting time (CT) with standard of care laboratory tests.

Methods: A retrospective analysis of pediatric ECMO patients at Phoenix Children’s Hospital from 7/2021 to 3/2024 who received heparin or bivalirudin was performed. Coagulation labs were included if they were drawn within one hour of each other. Correlation between INTEM/EXTEM CT with PT, aPTT, and anti-Xa was estimated using the Spearman rank coefficient stratified by anticoagulant.

Results: A total of 162 patients received ECMO with 1372 observations. Furthermore, 734 (54%) of patients received bivalirudin and 619 (46%) received heparin. For the heparin cohort, median age was 25 months (IQR 1-156) with median run time of 140 hours (IQR 67.5-241). For the bivalirudin cohort, median age was 6 months (IQR 2-60) with a median run time of 101 hours (IQR 77-223). The predominate indications for ECMO were cardiac arrest (25%), post cardiac bypass (22%), and cardiogenic shock (18%). For heparin, INTEM CT had a strong correlation with aPTT (r = 0.75, p < 0.0001) and a weak correlation with anti-Xa (r = 0.17, p = 0.0005). EXTEM CT had a weak correlation with PT (r = 0.21, p < 0.0001). For bivalirudin, INTEM CT had a moderate correlation with aPTT (r = 0.66, p < 0.0001) while EXTEM CT had a moderate correlation with PT (r = 0.58, p < 0.0001).

Conclusions: This study demonstrated a moderate to strong correlation between INTEM CT and aPTT for patients receiving heparin or bivalirudin. Anti-Xa had weak correlation to INTEM CT for patients receiving heparin. Further study on use of ROTEM during pediatric ECMO is warranted.