Complement activation and increased alveolar-capillary permeability after major surgery and in adult respiratory distress syndrome.

The concentrations of C3a des Arg were measured in bronchoalveolar fluid (BAL) and plasma from 12 patients with adult respiratory distress syndrome (ARDS). Compared with 32 controls, all patients had increased BAL fluid levels (p less than .001), and nine of 12 had increased plasma levels (p less than .001) of this split product from the third complement component. Reduced total hemolytic activity (CH50) in serum was seen in five patients (p less than .01). As an indication of damage to the alveolar-capillary barrier, ten of the 12 ARDS patients had elevated albumin concentrations in BAL fluid (p less than .001). These signs of complement activation and lung tissue damage are not specific for ARDS. Thus, in 15 patients investigated preoperatively and postoperatively, we found that major surgery induced a significant increase of BAL fluid C3a (p less than .01) and plasma C3a (p less than .02), a significant reduction of CH50 (p less than .001), and a significant increase of BAL fluid albumin (p less than .02). Similar values of CH50 and plasma C3a were seen in ARDS and after surgery (p greater than .05). Of the 12 ARDS patients, eight had increased BAL fluid concentrations of C3a (p less than .001), and ten had increased BAL fluid levels of albumin (p less than .001) compared with the post-surgical patients. Measuring complement consumption in blood by these techniques is of limited value in ARDS due to the lack of specificity. BAL fluid albumin has a similar degree of sensitivity and specificity for ARDS as does BAL fluid C3a.(ABSTRACT TRUNCATED AT 250 WORDS)