The ischaemic leg as a source of complement activation.

Complement activation before and after surgical resection was studied in 40 patients with ischaemic legs (17 with acute and 23 with chronic ischaemia). Plasma anaphylatoxin concentrations (C3a and C5a) and anaphylatoxin inhibitor (AI) activity were studied pre-operatively, and 1 h, 24 h and 1 week postoperatively. Increased plasma anaphylatoxin concentrations were found pre-operatively. Anaphylatoxin levels in plasma had returned to normal one week postoperatively. Patients with acute ischaemia had higher plasma C3a and C5a pre-operatively and during the first 24 h postoperatively than patients with chronic ischaemia. Anaphylatoxins increase vascular permeability, smooth muscle contraction and histamine release from mast cells. Their enhanced activity might be one of the explanations for respiratory, hepatic and renal insufficiency before surgical resection in patients with extensive ischaemia.