Effect of acute lung injury and acute respiratory distress syndrome on outcome in critically ill trauma patients*

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Abstract
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are known to be associated with increased mortality and costs in trauma patients. We estimated the independent impact of these conditions on mortality and cost, beyond the severity of injury with which they are correlated. One-year prospective cohort. All trauma patients admitted to the intensive care unit in a level I center were evaluated daily for ALI/ARDS using the American-European Consensus Conference definition. The main outcome measures were hospital mortality and costs. Logistic regression was used to model hospital mortality in relation to the presence of ALI and ARDS, adjusting for trauma severity (Injury Severity Score), Acute Physiology Score, and age. Hospital costs were modeled using multivariable linear regression. Of the 1,296 trauma patients surviving beyond the first day, 4% experienced ALI (defined as Pao2/Fio2 of 201–300 mm Hg) and 12% had ARDS (Pao2/Fio2 ≤ 200 mm Hg). The crude relative risk of mortality was 2.24 (95% confidence interval, 0.92–5.45) in patients with ALI and 3.84 (95% confidence interval, 2.41–6.13) in patients with ARDS compared with those without ALI/ARDS. However, there was no association of mortality with ALI (relative risk, 0.99; 95% confidence interval, 0.29–3.36) or with ARDS (relative risk, 1.23; 95% confidence interval, 0.63–2.43) after adjustment for age, Injury Severity Score, and Acute Physiology Score. Among patients of comparable age, severity score, and length of stay, median cost was 20% to 30% higher for those with ALI/ARDS. There is no additional mortality associated with ALI/ARDS above and beyond the factors that can be measured at intensive care unit admission. Therefore, mortality in trauma patients is explained by injury severity at admission and is not affected by the subsequent occurrence of ALI/ARDS. Nonetheless, ALI/ARDS was associated with increased intensive care unit stay and hospital cost, independent of trauma severity.