Prognostic accuracy of oxygen debt for mortality in patients undergoing venoarterial extracorporeal membrane oxygenation therapy: a retrospective cohort study

Background Cardiogenic shock is associated with high mortality. Prognostic scales, such as Sequential Organ Failure Assessment (SOFA), Acute Physiology and Chronic Health Evaluation II (APACHE II), and Survival After Venoarterial ECMO (SAVE), have been used to estimate mortality risk or survival probability. However, their performance remains limited in the context of Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO) therapy. This study aimed to validate oxygen debt (DEOx) as a predictor of 28-day mortality in critically ill patients receiving VA-ECMO and to compare its prognostic accuracy with that of the SAVE, SOFA, and APACHE II scores. Methods This retrospective cohort study included patients with cardiogenic shock admitted to the intensive care unit. All patients were prescribed VA-ECMO therapy in accordance with criteria by the Extracorporeal Life Support Organization. Upon initiation of ECMO, the APACHE II, SOFA, and SAVE scores, calculated 6 h prior to cannulation, and the DEOx score were compared for their predictive ability for 28-day mortality. Results A total of 157 patients were included, with a mortality of 40% (63/157). Of these, 56.7% (89/157) were male. Mean DEOx was 11.4 mL O₂/kg. Mean age was 46.6 years (standard deviation 13.8). In multivariate analysis, variables independently associated with 28-day mortality included DEOx (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.01–1.06; p  = 0.001), pre-ECMO infection (OR: 2.86; 95% CI: 1.20–6.80; p  = 0.018), hypertension (OR: 2.66; 95% CI: 1.22–5.78; p  = 0.014), and APACHE II (OR: 1.08; 95% CI: 1.01–1.16; p  = 0.018). Area under the curve (AUC) analysis revealed weak discrimination and similar performance regarding the primary outcome. DEOx showed the highest discrimination (AUC 0.663, 95% CI 0.49–0.77), followed by SAVE transformed to mortality (0.625), APACHE II (0.611), and SOFA (0.595). Conclusion In adults receiving VA-ECMO for refractory cardiogenic shock, DEOx measured 6 h before ECMO cannulation showed modest discrimination for 28-day mortality and higher specificity than SOFA and SAVE at pre-specified thresholds. These findings support DEOx as a potential complementary early risk indicator; however, we did not evaluate integrated models with existing scores. Prospective, multicentre studies should evaluate whether adding DEOx to APACHE II/SOFA/SAVE improves prognostic performance and supports earlier intervention.