The impact of development of acute lung injury on hospital mortality in critically ill trauma patients.

OBJECTIVE

The additional impact of development of acute lung injury on mortality in severely-injured trauma patients beyond baseline severity of illness has been questioned. We assessed the contribution of acute lung injury to in-hospital mortality in critically ill trauma patients.

DESIGN

Prospective cohort study. The contribution of acute lung injury to in-hospital mortality was evaluated in two ways. First, multivariable logistic regression models were used to test the independent association of acute lung injury with in-hospital mortality while adjusting for baseline confounding variables. Second, causal pathway models were used to estimate the amount of the overall association of baseline severity of illness with in-hospital mortality that is attributable to the interval development of acute lung injury.

SETTING

Academic level 1 trauma center.

PATIENTS

Two hundred eighty-three critically ill trauma patients without isolated head injury and with an Injury Severity Score > or = 16 were evaluated for development of acute lung injury in the first 5 days after trauma.

MEASUREMENTS AND MAIN RESULTS

Of the 283 patients, 38 (13.4%) died. The unadjusted mortality rate was nearly three-fold greater in the acute lung injury group (23.9% vs. 8.4%; odds ratio = 3.36; 95% confidence interval 1.67-6.77; p = 0.001). Acute lung injury remained an independent risk factor for death after adjustment for age, baseline Acute Physiologic and Chronic Health Evaluation III score, Injury Severity Score, and blunt mechanism of injury (odds ratio = 2.87; 95% confidence interval 1.29-6.37; p = 0.010). Forty percent of the total association of the baseline Acute Physiologic and Chronic Health Evaluation III score with mortality occurred via an indirect association through acute lung injury, and the remaining 60% via a direct effect.

CONCLUSIONS

Development of acute lung injury in critically ill trauma patients without isolated head injury contributes independently to in-hospital mortality beyond baseline severity of illness measures. In addition, a significant portion of the association between baseline illness severity and risk of death in these patients might be explained by the interval development of acute lung injury.