In twenty patients who underwent a knee arthrotomy in which a pneumatic
tourniquet was employed, there was a significant increase in fibrinolytic
activity (measured by the amount of time for the lysis of euglobulin and by
the fibrin-plate method) in the systemic circulation which peaked at
fifteen minutes and lasted for thirty minutes after release of the
tourniquet. No rebound occurred thereafter. The concentration of fibrinogen
and the platelet count decreased and the concentration of the products of
fibrin degradation increased after deflation of the tourniquet. Arterial
PO2, PCO2, and pH were changed significantly. In contrast, fibrinolytic
activity did not increase in patients undergoing operations on the lower
extremity without a tourniquet. Deep-vein thrombosis developed in two
patients who were treated with a tourniquet and in seven patients in whom a
tourniquet was not used. We concluded that increased fibrinolytic activity,
presumably mediated through enhanced release of plasminogen activator,
might be partly responsible for the decreased incidence of venous
thrombosis in the patients in this study for whom a tourniquet was
used.