Generation of anaphylatoxin C3a in plasma and bronchoalveolar lavage fluid in trauma patients at risk for the adult respiratory distress syndrome.

Objective: To determine the generation of anaphylatoxin C3a in plasma and bronchoalveolar lavage fluid in trauma patients at risk for the adult respiratory distress syndrome (ARDS).

Design: Prospective study.

Setting: ICU in a university hospital.

Patients: Severely traumatized patients at risk for the ARDS (n = 25).

Intervention: EDTA plasma samples and bronchoalveolar lavage fluid were obtained.

Measurements And Main Results: Complement proteins C3, C4, C5, and the inhibitors C1-inhibitor, Factor H, and Factor I were quantitated in EDTA-plasma samples obtained every 6 hrs during the first 48 hrs after ICU admission and every morning from days 4 to 14 after injury. In bronchoalveolar lavage fluid, the complement activation production of C3a-desArg was quantitated and the volume of epithelial lining fluid was calculated. All patients showed a decrease of the complement proteins C3, C4, C5 and of the inhibitors C1-inhibitor, Factor H, and Factor I during the first 24 hrs, indicating complement consumption. Patients developing ARDS (n = 11) showed significantly higher C3 concentrations and a higher C3a/C3 ratio in the first few hours after multitrauma. Follow-up bronchoalveolar lavages demonstrated highly increased amounts of C3a in epithelial lining fluid during the first 24 hrs, mainly in ARDS patients and, to a lesser degree, in non-ARDS patients. To determine the origin of C3a in bronchoalveolar lavages, the ratio of C3a in epithelial lining fluid and plasma was calculated.

Conclusion: The C3a of epithelial lining fluid to plasma ratio was extremely high in patients developing ARDS, but even the non-ARDS group had a ratio greater than 1, indicating that a substantial local complement activation occurs in the lung.