Predictive Potential of ECMO Blood Flow for Hemolysis and Outcome of Patients with Severe ARDS

Background: Treatment with veno-venous extracorporeal membrane oxygenation (VV ECMO) has become a frequently considered rescue therapy in patients with severe acute respiratory distress syndrome (ARDS). Hemolysis is a common complication in patients treated with ECMO. Currently, it is unclear whether increased ECMO blood flow (Q̇_EC) contributes to mortality and might be associated with increased hemolysis. Methods: A total of 441 patients with ARDS and VV ECMO, treated in a tertiary ARDS center, were included. The Q̇_EC value for a significant increase in ICU mortality was determined by binary recursive partitioning. Linear regression analysis was performed to analyze a correlation between mean Q̇_EC and mean plasma concentrations of cell-free hemoglobin (CFH). Results: A Q̇_EC of 4 L/min divided the cohort into two groups with significantly different ICU mortality (Q̇_EC ≤ 4 L/min: 39.3% (n = 300) versus Q̇_EC > 4 L/min: 71.6% (n = 141), p < 0.001). Patients with Q̇_EC > 4 L/min had a higher 28-day mortality. Furthermore, a higher mean Q̇_EC was associated with increased CFH and decreased haptoglobin plasma concentrations. Conclusion: In patients with ARDS and VV ECMO, a mean Q̇_EC > 4 L/min is associated with increased mortality, increased CFH and decreased haptoglobin plasma concentrations. Whether increased hemolysis determines the poorer outcome associated with higher Q̇_EC should be the subject of future research.