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.