Objective: To elucidate the role of pulmonary neutrophil accumulation in the pathogenesis of human acute lung injury (ALI) following endotoxemia.
Design: Retrospective study.
Setting: Surgical unit in a tertiary-care university hospital.
Patients: Thirty-three patients who died of intra-abdominal sepsis and received an autopsy.
Measurements: Just before each patient's death, (1) plasma endotoxin was determined by the limulus gelation test, and (2) the severity of ALI was estimated by the Murray lung injury score. (3) Neutrophil accumulation in the pulmonary microcirculation was evaluated in the autopsy specimens using a computerized picture analysis method.
Results: (1) Endotoxin-positive patients were more likely to fall into the severe lung injury group (endotoxin-positive patients, 38% vs endotoxin-negative patients, 0%; p < 0.01). (2) The endotoxin-positive patients exhibited significantly higher neutrophil accumulation in the pulmonary microcirculation than endotoxin-negative patients (8,349 +/- 984/mm(2) vs 4,047 +/- 447/mm(2), respectively; p < 0.01). (3) Severe lung injury patients with endotoxemia had almost the same degree of neutrophil accumulation in the pulmonary microcirculation as mild-to-moderate lung injury patients with endotoxemia (8,338 +/- 1,622/mm(2) vs 8, 359 +/- 1,290/mm(2), respectively), showing a significant higher neutrophil accumulation compared to no lung injury patients without endotoxemia (5,102 +/- 410/mm(2); p < 0.01).
Conclusion: Endotoxemia might cause ALI and pulmonary neutrophil accumulation. Pulmonary neutrophil accumulation might not be enough to cause severe lung injury (ARDS), although it is necessary to cause ALI, because the degree of pulmonary neutrophil accumulation did not correlate with the severity of ALI.