Predicting mortality risk in patients undergoing venovenous ECMO for ARDS due to influenza A (H1N1) pneumonia: the ECMOnet score

PURPOSE: The decision to start venovenous extracorporeal membrane oxygenation (VV ECMO) is commonly based on the severity of respiratory failure, with little consideration of the extrapulmonary organ function. The aim of the study was to identify predictors of mortality and to develop a score allowing a better stratification of patients at the time of VV ECMO initiation. METHODS: This was a prospective multicenter cohort study on 60 patients with influenza A (H1N1)-associated respiratory distress syndrome participating in the Italian ECMOnet data set in the 2009 pandemic. Criteria for ECMO institution were standardized according to national guidelines. RESULTS: The survival rate in patients treated with ECMO was 68 %. Significant predictors of death before ECMO institution by multivariate analysis were hospital length of stay before ECMO institution (OR = 1.52, 95 % CI 1.12-2.07, p = 0.008); bilirubin (OR = 2.32, 95 % CI 1.52-3.52, p < 0.001), creatinine (OR = 7.38, 95 % CI 1.43-38.11, p = 0.02) and hematocrit values (OR = 0.82, 95 % CI 0.72-0.94, p = 0.006); and mean arterial pressure (OR = 0.92, 95 % CI 0.88-0.97, p < 0.001). The ECMOnet score was developed based on these variables, with a score of 4.5 being the most appropriate cutoff for mortality risk prediction. The high accuracy of the ECMOnet score was further confirmed by ROC analysis (c = 0.857, 95 % CI 0.754-0.959, p < 0.001) and by an independent external validation analysis (c = 0.694, 95 % CI 0.562-0.826, p = 0.004). CONCLUSIONS: Mortality risk for patients receiving VV ECMO is correlated to the extrapulmonary organ function at the time of ECMO initiation. The ECMOnet score is a tool for the evaluation of the appropriateness and timing of VV ECMO in acute lung failure.