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Patients undergoing extracorporeal membrane oxygenation (ECMO) have a high risk of developing multiple organ dysfunction, including acute kidney injury (AKI), with a reported incidence as high as 85% in some cohorts and requirement of renal replacement therapy in 55% of cases. Continuous renal replacement therapy (CRRT) is usually the preferred dialyisis modality and there is wide practice variation regarding the specifics of the therapy.
We aim to evaluate differences on outcomes and characteristics between patients undergoing different modalities of ECMO and CRRT.
Retrospective, observational study of patients undergoing ECMO in Mexico’s National Institute of Cardiology between 2022 and 2023.
31 patients undergoing ECMO were included. 21 (80%) developed AKI and 13 (42%) required CRRT. The most frequent indication was fluid overload (69%) followed by metabolic acidosis (23%). Of patients undergoing CRRT, 9 (69%) had veno-venous ECMO support, with the most frequent diagnosis being acute respiratory distress syndrome (ARDS) in 46% followed by chronic pulmonary hypertension undergoing planned thromboendarterectomy (15.4%), alveolar hemorrhage, myocarditis, right sided heart failure and antiphospholipid syndrome (7%). On patients that did not require CRRT, 83% underwent veno-arterial ECMO support due to acute myocardial infarction and planned cardiac surgery (22%), followed by endocarditis (16%), acute heart failure (11%) and acute aortic syndrome (5.6%). Mortality in both groups was 46.7%; 30.8% in the CRRT group and 55.6% in the non CRRT group. Among factors associated with the need for CRRT, we found the use of veno-venous ECMO (p = 0.003), diagnosis of ARDS (p = 0.026), and a longer duration of ECMO (p = 0.018). Patients that underwent veno-arterial ECMO had lower systolic (p = 0.032) and diastolic blood pressure (0.042) and more frequent requirement for vasopressor medication on admission (p = 0.056), as well as higher levels of troponin (p = 0.016) and natriuretic peptide (p = 0.019).
The main factor associated with the requirement of CRRT was the use of veno-venous ECMO due to predominantly pulmonary pathologies such as ARDS, chronic pulmonary hypertension undergoing thromboendarterectomy and alveolar hemorrhage. This patients had a significantly longer hospitalization and duration on ECMO.
Mortality was higher in patients that did not require CRRT, however, most of this patients underwent veno-arterial ECMO due to cardiogenic shock and were more severely ill as suggested by blood pressure, requirement of vasopressors on admission and higher levels of troponin and natriuretic peptide. Interestingly, despite the higher mortality of the group, requirement of CRRT was markedly lower. Perhaps the full cardiac and pulmonary support provided by veno-arterial ECMO prevents and/or improves hemodynamic AKI, assuring adequate perfusion to the kidneys. On the other hand the higher requirement of CRRT in patients undergoing veno-venous ECMO with the main indication of fluid overload could reflect the complex reno-pulmonary interactions that promote pulmonary and systemic congestion.