Objective: The immunoinflammatory response is central to the pathogenesis of acute respiratory distress syndrome (ARDS). However, little is known how this is affected by venovenous (VV) extracorporeal membrane oxygenation (ECMO). Our objective was to investigate the factors that influence the inflammatory response of patients with ARDS undergoing VV ECMO, and to analyse the impact of this response on hospital mortality.
Design and setting: A prospective observational study of all consecutive patients with severe ARDS who had VV ECMO at a tertiary German ECMO centre from 2009 to 2015. Patients without complete datasets were excluded. Cytokines (interleukin [IL]6, IL8 and tissue necrosis factor [TNF]α) and inflammatory markers (white cell count and C-reactive protein) were assessed before ECMO initiation and on Days 1, 5 and 10, before explantation and at explantation.
Results: A total of 262 adult patients undergoing VV ECMO were analysed. Their median Sequential Organ Failure Assessment score was 12, PaO2/FiO2 ratio was 64 mmHg, and overall in-hospital mortality was 34%. Cytokine levels fell quickly within 24 hours and fell further over the first 5 days. Extra-pulmonary ARDS was associated with higher IL6 and IL8 levels compared with pulmonary ARDS. Mechanical ventilation with positive end-expiratory pressure ≥ 15 cmH2O before ECMO was associated with higher IL6, IL8 and TNFα levels. Driving pressures ≥ 19 cmH2O before ECMO were associated with higher IL8 levels. Non-survivors had higher IL6 and IL8 levels for the duration of ECMO.
Conclusion: Cytokine levels, on average, fall rapidly after initiation of VV ECMO, which may be related to the reduction of invasiveness of mechanical ventilation. Higher cytokine levels are associated with extrapulmonary causes of ARDS, more aggressive mechanical ventilation before VV ECMO, and mortality.