(525) Bleeding Definitions in Extracorporeal Membrane Oxygenation (ECMO) Studies

Introduction: Extracorporeal Membrane Oxygenation (ECMO) supports severe cardio-respiratory failure but carries a significant bleeding risk, increasing morbidity, hospital stays, and mortality. Bleeding definitions vary widely across ECMO studies, often based on interventions like transfusions or surgeries. This introduces variability due to different practices and subjective decisions, potentially underestimating true bleeding incidence. This systematic review aims to report bleeding definitions in studies involving neonates and children treated with ECMO, and to determine how many studies rely on interventions in their definitions.

Methods: We conducted a systematic review and meta-analysis using multiple electronic databases, including all studies from database inception until April 26, 2024. We evaluated the description of bleeding definitions and the reported prevalence of bleeding on ECMO. Random-effect models were utilized to pool proportions, assuming each study estimated a study-specific true effect.

Results: Out of 6482 screened studies, 173 were included (156,096 subjects). Intracranial hemorrhage (ICH) and the ELSO definition were the most common bleeding definitions, used in 34 and 33 studies, respectively, with 70 different combinations overall. ICH alone or with other sites was used in 80% of studies, gastrointestinal bleeding in 47%, surgical site bleeding in 38%, pulmonary bleeding in 38%, cannula site bleeding in 34%, chest tube bleeding in 12%, and retroperitoneal bleeding in 5%. Therapies were included in bleeding definitions in 54% of the studies: transfusion (48%), procedures/interventions (35%), and anticoagulation adjustment (2%). The pooled prevalence of bleeding was 40.5% in studies using the ELSO definition (95% CI 34.9; 46.2, I²=99.6%, n=58,869) and 34.0% in studies using other definitions (95% CI 31.3; 36.8, I²=99.4%, n=97,227).

Conclusions: Bleeding occurs in over a third of ECMO patients, with high variability in definitions. More than half of the studies define bleeding based on interventions or transfusions, leading to risks due to variable clinical practices and potential under- or overestimation of bleeding incidence. Standardized definitions are needed to improve the comparability and understanding of bleeding risks in ECMO patients, irrespective of the interventions.