Fibrinolysis after application of a pneumatic tourniquet.

The fibrinolytic system was studied after application of a pneumatic tourniquet in 22 patients undergoing elective orthopaedic surgery and during 20-min venous occlusion in 17 healthy subjects. Blood was sampled before anaesthesia (A), before operation (B) and after operation from the ipsilateral (C) and the contralateral (D) limb. Tissue plasminogen activator (t-PA) activity, t-PA antigen and t-PA activity/t-PA antigen ratio increased by, respectively, 557, 109 and 168% in the C samples as compared with A blood (all differences statistically significant). The t-PA activity and t-PA antigen increased slightly in the systemic circulation (B and D) but were significantly less in C than after venous occlusion. Fast-acting inhibitor of t-PA increased significantly in C (15%). During compression with a pneumatic tourniquet, mainly local fibrinolytic activation occurs, and this activation partly explains the low incidence of postoperative deep venous thrombosis after use of a tourniquet.