Extravascular lung water is an independent prognostic factor in patients with acute respiratory distress syndrome*

Abstract

Acute respiratory distress syndrome might be associated with an increase in extravascular lung water index and pulmonary vascular permeability index, which can be measured by transpulmonary thermodilution. We tested whether extravascular lung water index and pulmonary vascular permeability index are independent prognostic factors in patients with acute respiratory distress syndrome. Retrospective study. Medical intensive care unit. Two hundred consecutive acute respiratory distress syndrome patients (age = 57 ± 17, Simplified Acute Physiology Score II = 57 ± 20, overall day-28 mortality = 54%). Extravascular lung water index and pulmonary vascular permeability index were collected (PiCCO device, Pulsion Medical Systems) at each day of the acute respiratory distress syndrome episode. The maximum values of extravascular lung water index and pulmonary vascular permeability index recorded during the acute respiratory distress syndrome episode (maximum value of extravascular lung water index and maximum value of pulmonary vascular permeability index, respectively) were significantly higher in nonsurvivors than in survivors at day-28 (mean ± SD: 24 ± 10 mL/kg vs. 19 ± 7 mL/kg of predicted body weight, p < 0.001 [t-test] for maximum value of extravascular lung water index and median [interquartile range]: 4.4 [3.3-6.1] vs. 3.5 [2.8-4.4], p = 0.001 for maximum value of pulmonary vascular permeability index, Wilcoxon's test). In multivariate analyses, maximum value of extravascular lung water index or maximum value of pulmonary vascular permeability index, Simplified Acute Physiology Score II, maximum blood lactate, mean positive end-expiratory pressure, mean cumulative fluid balance, and the minimal ratio of arterial oxygen pressure over the inspired oxygen fraction were all independently associated with day-28 mortality. A maximum value of extravascular lung water index >21 mL/kg predicted day-28 mortality with a sensitivity of (mean [95% confidence interval]) 54% (44-63)% and a specificity of 73% (63-82)%. The mortality rate was 70% in patients with a maximum value of extravascular lung water index >21 mL/kg and 43% in the remaining patients (p = 0.0003). A maximum value of pulmonary vascular permeability index >3.8 predicted day-28 mortality with a sensitivity of (mean [95% confidence interval]) 67% (57-76)% and a specificity of 65% (54-75)%. The mortality rate was 69% in patients with a maximum value of pulmonary vascular permeability index >3.8 and 37% in the group with a maximum value of pulmonary vascular permeability index ≤ 3.8 (p < 0.0001). Extravascular lung water index and pulmonary vascular permeability index measured by transpulmonary thermodilution are independent risk factors of day-28 mortality in patients with acute respiratory distress syndrome.