Prognostic value of surfactant proteins A and D in patients with acute lung injury

Objective: The primary objective of this study was to test the hypothesis that in patients intubated for acute lung injury, lower concentrations of surfactant proteins A and D in the pulmonary edema fluid and higher concentrations in the plasma are associated with more severe lung injury and worse clinical outcomes. Design: Observational study. Setting: Intensive care unit patients in a tertiary university hospital and a university-affiliated city hospital. Patients: Thirty-eight intubated, mechanically ventilated intensive care unit patients with acute lung injury or acute respiratory distress syndrome as defined by the North American European Consensus Conference. Interventions: Undiluted pulmonary edema fluid and plasma samples were collected within 24 hrs of endotracheal intubation in all patients. Measurements and Main Results: The concentrations of surfactant proteins A and D were measured in pulmonary edema fluid and in plasma. Plasma surfactant protein A, but not surfactant protein D, was higher in patients with fewer days of unassisted ventilation (p = .03) and in patients with an absence of intact alveolar fluid clearance (p = .03). In contrast, pulmonary edema fluid surfactant protein D, but not surfactant protein A, was lower in patients with worse oxygenation, as measured by the alveolar-arterial oxygen difference (p = .01) and was lower in the patients who died (2646 ng/mL) compared with those who survived (5503 ng/mL; p = .02). Conclusions: These results demonstrate that reduced pulmonary edema fluid surfactant protein D and elevated plasma surfactant protein A concentrations at the onset of acute lung injury may be associated with more severe disease and worse clinical outcome and may serve as valuable biochemical markers of prognosis.