Predictors of Early Acute Lung Injury at a Combat Support Hospital: A Prospective Observational Study

Background: Acute lung injury (ALI) is a syndrome consisting of noncardiogenic acute hypoxemic respiratory failure with the presence of bilateral pulmonary infiltrates and occurs in up to 33% of critically ill trauma patients. Retrospective and observational studies have suggested that a blood component resuscitation strategy using equal ratios of packed red blood cells (PRBCs) and fresh frozen plasma (FFP) may have a survival benefit in combat casualties. The purpose of this study was to determine whether this strategy is associated with an increased incidence of ALI. Methods: We performed a prospective observational study of all injured patients admitted to an intensive care unit (ICU) at a combat support hospital who required >5 units of blood transfusion within the first 24 hours of admission. Baseline demographic data along with Injury Severity Score (ISS), pulmonary injury, presence of long bone fracture, blood products transfused, mechanical ventilation data, and arterial blood gas analysis were collected. The primary endpoint of the study was the development of ALI at 48 hours after injury. Those who did not survive to ICU admission were excluded from analysis. Follow-up (including mortality) longer than 48 hours was unavailable secondary to rapid transfer out of our facility. A multivariate logistic regression was performed to determine the independent effects of variables on the incidence of early ALI. Results: During a 12-month period (from January 2008 to December 2008), 87 subjects were studied; of these, 66 patients met inclusion criteria, and 22 patients developed ALI at 48 hours (33%). Overall, the ratio of FFP to PRBC was 1:1.1. Those who developed ALI had a higher ISS (32 +/- 15 vs. 26 +/- 11; p = 0.04) and received more units of FFP (22 +/- 15 vs. 12 +/- 7; p < 0.001), PRBCs (22 +/- 16 vs. 13 +/- 7; p = 0.008), and platelets (5 +/- 11 vs. 1 +/- 2; p = 0.004) compared with those who did not develop ALI. Multivariate logistic regression analysis revealed that presence of pulmonary injury (odds ratio, 5.4; 95% confidence interval, 1.3-21.9) and volume of FFP transfused (odds ratio, 1.2; 95% confidence interval, 1.1-1.3) had independent effects on ALI at 48 hours. Conclusion: On the basis of this small, prospective, descriptive study of severely injured patients admitted to the ICU, we determined that the presence of pulmonary injury had the greatest impact on the incidence of early ALI. There was also an independent relationship between the amount of FFP transfused and the incidence of early ALI. Further studies are required to determine the effects of the development of early ALI from FFP transfusion on short- and long-term survival.