During extracorporeal membrane oxygenation (ECMO) systemic anticoagulation with unfractionated heparin (UFH) is standard-of-care. However, there is uncertainty regarding optimal anticoagulation monitoring strategies.

We retrospectively investigated venovenous and venoarterial ECMO patients at the medical ICUs at the Medical University of Graz, Austria. We analyzed the correlation and concordance of R-time in thromboelastography (TEG), activated partial thromboplastin time (aPTT), and anti-Xa activity. The proportion within target range, the association of coagulation parameters above or below target range (aPTT 54–72 s; equals 1.5–2× upper limit of normal (ULN), anti-Xa activity 0.2–0.5 U/mL, and R-time in assays without heparinase 675–900 s; equals 1.5–2× ULN) with mortality, bleeding events and thrombotic complications were investigated.

We analyzed 671 clusters of simultaneously performed coagulation tests in 85 ECMO cases that fulfilled inclusion criteria. Median age of patients was 57 years and 32% were female. There were poor correlations between the three coagulation tests and the proportion of discordance was 46%. Within the target range were 21% of R-time, 15% of aPTT, and 44% of anti-Xa activity measurements. Singular and multiple bleeding events occurred in 25 and 32 patients, respectively. The most common bleeding locations were catheter and cannula insertion sites followed by pulmonary hemorrhage. In VA-ECMO, anti-Xa activity was associated (OR 1.03 [1.01–1.06], p = 0.005) and correlated with bleeding events (spearman rho 0.49, p = 0.002; point biserial 0.49, p = 0.001). aPTT level below target range was associated with reduced mortality (OR 0.98 [0.97–0.99], p = 0.024). Thrombotic events occurred in six patients with no association of coagulation tests.

There was a high rate of discordance and poor correlation between aPTT, anti-Xa activity and R-time in TEG in ECMO patients. We found high rates of bleeding events and in VA-ECMO an association with elevated anti-Xa activity levels.