Role of Serum Cytokine Levels in Acute Respiratory Distress Syndrome Patients on Extracorporeal Membrane Oxygenation Support

Background: Even with the use of extracorporeal membrane oxygenation (ECMO) in acute respiratory distress syndrome (ARDS), mortality remains high. Also, prognostication of patients with ARDS and ECMO is difficult. Cytokines are thought to be markers of inflammation in both ARDS and in ECMO, however, understanding is limited. We aimed to study the association of three serum cytokine levels with mortality in these patients with ARDS on ECMO. Methods: We performed a retrospective chart review of ARDS patients on ECMO between 2011 and 2017. Patients with serum TNF-α, IL-6 and IL-2 measured while on ECMO were included, with measurements recorded weekly up to a maximum of 4 measurements. A multivariable regression analysis was performed and generalizing estimating equations were used to analyze longitudinal trend of cytokines with mortality. Results: There were 47 patients with ARDS on ECMO, of which 31 (68.9%) survived at 30 days and 2 were lost to follow up. Initial IL-2 levels were found to be significantly higher among those who were alive compared to those who died at 30 days (2720 ± 2432 pg/ml vs. 1293 ± 693 pg/ml); p = 0.0460. At any given time, an increase in IL-2 was associated with a decrease in odds of death at 30 days (adjusted odds ratio 0.98, 95% confidence interval 0.97 - 0.99, p = 0.08). There was no significant difference in average or initial levels of TNF-α and IL-6 among those who were alive vs. those who died at 30 days. There was no association between either of these cytokine levels with death while on ECMO. Conclusions: Higher levels of cytokine IL-2 were associated with lower 30-day mortality. Further studies are needed to elucidate the pathobiology of cytokines while on ECMO and their use in predicting outcomes.