No abstract

Acute respiratory distress syndrome (ARDS) involves an intense inflammatory response in the lungs, with accumulation of both pro- and antiinflammatory cytokines in bronchoalveolar lavage fluid (BALF). Our goal was to determine how the balance between pro- and antiinflammatory mediators in the lungs changes before and after the onset of ARDS. We identified 23 patients at risk for ARDS and 46 with established ARDS and performed serial bronchoalveolar lavage (BAL). We used immunoassays to measure tumor necrosis factor alpha (TNF-alpha) and soluble TNF-alpha receptors I and II; interleukin 1 beta (IL-1 beta), IL-1 beta receptor antagonist, and soluble IL-1 receptor II; IL-6 and soluble IL-6 receptor; and IL-10. We used sensitive bioassays to measure net TNF-alpha, IL-1 beta, and IL-6 activity. Although individual cytokines increased before and after onset of ARDS, greater increases occurred in cognate receptors and/or antagonists, so that molar ratios of agonists/antagonists declined dramatically at the onset of ARDS. The molar ratios remained low for 7 d or longer, limiting the activity of soluble IL-1 beta and TNF-alpha in the lungs at the onset of ARDS. This significant antiinflammatory response early in ARDS may provide a key mechanism for limiting the net inflammatory response in the lungs.

These results do not support the routine use of methylprednisolone for persistent ARDS despite the improvement in cardiopulmonary physiology. In addition, starting methylprednisolone therapy more than two weeks after the onset of ARDS may increase the risk of death. (ClinicalTrials.gov number, NCT00295269.).

To determine the relationship between airspace cytokines and cellular inflammatory responses in patients with the acute respiratory distress syndrome (ARDS), we performed bronchoalveolar lavage (BAL) in 82 prospectively identified, mechanically ventilated patients on Days 3, 7, 14, and/or 21 after the onset of ARDS. We studied the relationships between bronchoalveolar lavage fluid (BALF) cell populations and the concentrations of two potent neutrophil (PMN) chemoattractants, interleukin-8 (IL-8) and epithelial cell-derived neutrophil activator-78 (ENA-78); two potent monocyte chemoattractants, monocyte chemotactic peptide-1 (MCP-1) and macrophage inflammatory peptide-1 alpha (MIP-1 alpha); and the early response cytokine interleukin-1 beta (IL-1 beta) and its naturally occurring antagonist, IL-1 receptor antagonist protein (IRAP). We found that all of these cytokines were significantly increased regardless of the duration of ARDS. IL-8 and ENA-78 were the cytokines most strongly and consistently correlated with PMN concentrations in the lung fluids of patients with ARDS, and the correlations were independent of the other cytokines or coexisting lung infection. None of the cytokines tested correlated with macrophage concentrations. MCP-1 was directly correlated with lung injury score on Days 7, 14, and 21. Although neither IL-8 nor ENA-78 was associated with outcome, levels of IL-1 beta measured on Day 7 were associated with an increased risk of death (odds ratio [OR] = 2.8; 95% confidence interval [CI] = 1.1 to 7.4). These data demonstrate potential molecular mechanisms of the persistent inflammatory process in the lungs of patients with ARDS.