The susceptibility of plasma to activation of fibrinolysis.

The susceptibility of blood to fibrinolytic activation is an important parameter to predict the possible clinical outcome of thrombolysis in routine hospital practice. This paper describes a rapid method which is based on the integrated plasmin activity of a sample and which therefore does not require standardization of different fibrinolytic factors, such as plasminogen activator inhibitor type 1. Plasma is incubated with either streptokinase, urokinase (u-PA), tissue plasminogen activator (t-PA) or plasminogen streptokinase activator complex (PSAC) at room temperature. This is followed by addition of KCl, the chromogenic plasmin substrate S-2251 and chloramine T. As a blank, KCl is added before the enzyme. The incubation time is shortened three-fold at 37 degrees C. The highest fibrinolytic activity, with the smallest standard deviation, was obtained with streptokinase. When the lowest activity measured was defined as 100%, the highest activities were 273%, 297%, 344% and 961% for streptokinase, urokinase, t-PA and APSAC respectively. The susceptibility to urokinase correlated with that of t-PA. Patients reacted differently to the different plasminogen activators. Therefore, the method allows the appropriate agent and amount to be chosen before thrombolysis is started.