Objective: To study the major eicosanoids implicated in the pathophysiology of acute respiratory distress syndrome (ARDS) in order to estimate their relative prognostic values.
Methods: We conducted a prospective study in a consecutive series of patients with ARDS admitted to a university hospital intensive care unit. We measured the plasma concentrations of 3 inflammatory mediators (thromboxane B(2), 6-keto prostaglandin F(1alpha), and leukotriene B(4)) in peripheral arterial and mixed venous plasma samples.
Results: We studied 16 patients with ARDS, who had a mean alpha SD baseline ratio of P(aO(2)) to fraction of inspired oxygen (P(aO(2))/F(IO(2))) of 147 +/- 37 mm Hg and a mean +/- SD baseline lung injury score of 2.9 +/- 0.37. The plasma concentrations of thromboxane B(2), 6-keto prostaglandin F(1alpha), and leukotriene B(4) were greater than the general-population reference levels in both arterial and mixed venous plasma, but only leukotriene B(4) was higher in arterial plasma than in mixed venous plasma (401 +/- 297 pg/mL vs 316 +/- 206 pg/mL, p = 0.04). When we correlated the eicosanoid concentrations with specific indicators of clinical severity, we found correlations only between the baseline P((aO2))/F(IO(2)) and the arterial thromboxane B(2) level (r = -0.57, p = 0.02), the arterial leukotriene B(4) level (r = -0.59, p = 0.01), and the transpulmonary gradient of leukotriene B(4) level (r = -0.59, p = 0.01). We also found a correlation between the transpulmonary gradient of leukotriene B(4) and the lung injury score (r = 0.51, p = 0.04). The thromboxane B(2) concentration in arterial plasma and the leukotriene B(4) concentration in both arterial and mixed venous plasma were the only baseline plasma eicosanoid concentrations that predicted significant differences in outcome. When looking at the transpulmonary gradient of the eicosanoids studied, we found that only the gradient of leukotriene B(4) showed significant differences of clinical interest. Among survivors we observed practically no gradient (-4.9%), whereas among nonsurvivors we found a substantial positive gradient of 41.6% for the elevated arterial (post-pulmonary) values, compared with the pulmonary-artery (pre-pulmonary) values, and this difference was statistically significant (p = 0.02).
Conclusions: The pro-inflammatory eicosanoid leukotriene B(4) showed the best correlation with lung-injury severity and outcome in patients with ARDS.