Renal replacement therapy in patients under extracorporeal membrane oxygenation: a narrative review

BACKGROUND: The use of extracorporeal membrane oxygenation (ECMO) has expanded for severe respiratory and circulatory failure. Acute kidney injury (AKI) is one of the most frequent complications. Up to 85% of ECMO patients develop AKI and approximately half of them require renal replacement therapy (RRT) making a comprehensive understanding of both therapies and their interaction essential for patient management. However, evidence to guide ECMO-specific RRT strategies remains limited. MAIN BODY: ECMO-related AKI arises from a complex interplay between patient and circuit factors that promote inflammation, endothelial injury, and tubular damage. Timing of RRT initiation in ECMO patients often relies on criteria used in the general critically ill population. Fluid overload is consistently associated with worse outcomes, and observational data suggest that earlier RRT, primarily to control fluid balance, may improve survival although randomized trials in ECMO patients are lacking. All RRT modalities can theoretically be used, but continuous techniques are preferred. RRT can be delivered via a parallel circuit using a dedicated venous catheter or integrated into the ECMO circuit. Integrated configurations reduce the need for additional vascular access and may prolong filter lifespan but require careful pressure management and team expertise to avoid alarms, hemolysis, and air embolism. Anticoagulation strategies must balance bleeding and thrombosis risk across both circuits; unfractionated heparin remains standard, while regional citrate anticoagulation can safely extend filter lifespan in selected patients although data is lacking in patients under veno-arterial ECMO. RRT during ECMO is associated with higher short-term mortality and an increased burden of chronic kidney disease among survivors. CONCLUSIONS: The management of AKI in ECMO patients remains a major clinical challenge. While RRT is often required in this population, optimal strategies for its initiation, modality selection, and integration with ECMO circuits are still evolving. Current evidence underscores the need for individualized approaches based on patient characteristics. Future research should focus on defining standardized protocols for RRT implementation in ECMO, use of regional citrate anticoagulation, optimizing patient selection, and evaluating long-term renal and survival outcomes.