Initial V‐A ECMO Flow‐Index and Its Association With Inflammation, Organ Failure, and Outcomes

Background Refractory cardiogenic shock remains associated with high mortality despite macrocirculatory stabilization with V‐A ECMO. We investigated the association between initial ECMO flow‐index, organ dysfunction, inflammatory activation, hemolysis, and clinical outcome. Methods In this retrospective single‐center study, 553 patients receiving V‐A ECMO between 2014 and 2024 were divided into low‐flow (< 1.63 L/min/m 2 , n = 269) and high‐flow (≥ 1.63 L/min/m 2 , n = 284) groups. Patients were additionally stratified according to eCPR status. Multivariable logistic regression was used to assess factors associated with multi‐organ failure (MOF), and exploratory mediation analyses evaluated day‐1 free hemoglobin and IL‐6 as potential mediators. Results High‐flow patients were more hemodynamically compromised, with higher lactate, vasoactive‐inotropic support, inflammatory markers, and early hemolysis. After exclusion of cerebral death, MOF occurred more frequently in the high‐flow group (32.7% vs. 23.0%, p = 0.028). Initial flow‐index remained independently associated with MOF in the overall cohort (OR 1.102 per 0.1 L/min/m 2 , 95% CI 1.001–1.214, p = 0.048) and in the eCPR subgroup (OR 1.117, 95% CI 1.028–1.214, p = 0.008). Day‐1 free hemoglobin was independently associated with MOF, and mediation analysis demonstrated a significant indirect effect through early hemolysis. No significant indirect effect through IL‐6 was observed. Higher flow index was also associated with worse neurological outcome and reduced survival. Conclusions Higher initial V‐A ECMO flow‐index is associated with greater shock severity and multi‐organ failure. Early hemolysis may partly contribute to this association, particularly in eCPR patients. These findings support individualized flow management with close monitoring of hemolysis and evolving organ dysfunction.