Abstract
BACKGROUND: Inflammation and immune status are essential in acute respiratory distress syndrome (ARDS), wherein excessive inflammation with severe immunosuppression is associated with a poor prognosis. This study investigated the interleukin-6 (IL-6) and lymphocyte count (Lym) in patients with moderate-to-severe ARDS supported by venovenous extracorporeal membrane oxygenation (VV ECMO), as well as their relationship with prognosis, providing new insights for clinical prognosis evaluation. METHODS: A single-center, retrospective cohort study was conducted using data collected between March 2022 and July 2024. A total of 117 patients with moderate-severe ARDS with VV ECMO support were enrolled in this study. The observational clinical outcome was intensive care unit (ICU) 28-day mortality. Cox proportional hazard regression analysis was used to determine the potential prognostic factors for ICU 28-day mortality. Receiver operating characteristic (ROC) curve analysis was used to evaluate and compare the prognostic factors for 28-day mortality. Kaplan-Meier survival curves were generated to compare the mortality, with log-rank tests used to analyze differences. RESULTS: Of 117 patients, 60 died in the ICU within 28 days. The survivors had higher Sequential Organ Failure Assessment (SOFA) scores, IL-6, and peak airway pressure (Ppeak), and had lower Lym. According to univariable Cox analysis, baseline SOFA score [hazard ratio (HR): 1.09, 95% confidence interval (CI) 1.02-1.18; P=0.02], baseline norepinephrine (NE) dose (HR: 2.13, 95% CI: 1.30-3.48; P=0.003), baseline lactate (HR: 1.13, 95% CI: 1.07-1.19; P<0.001), baseline static lung compliance (C(stat)) (HR: 0.97, 95% CI: 0.95-1.00; P=0.03), baseline IL-6/Lym >138.0 (HR: 4.85, 95% CI: 2.37-9.91; P<0.001), and baseline lactate (HR: 1.09, 95% CI: 1.03-1.15; P=0.003). Baseline IL-6/Lym >138.0 (HR: 4.73, 95% CI: 2.83-8.00; P<0.001) was shown to be an independent prognostic factor for ICU 28-day mortality with multivariate Cox analysis. The best discrimination between survivors and non-survivors was observed with the IL-6/Lym [area under the ROC curve (AUROC): 0.80, 95% CI: 0.69-0.88]. CONCLUSIONS: IL-6/Lym may be an independent protective factor for predicting ICU 28-day mortality in patients with moderate-to-severe ARDS supported with VV ECMO. The conclusions of the study need to be further confirmed by a multicenter prospective study.