Plasmin, plasmin inhibitors, and degradation products of fibrinogen in human serum during and after intravenous infusion of streptokinase.

A. AMERY, J. VERMYLEN, AND M. VERSTRAETE (Leuven University, Belgium) This study compares the effect on fibrinogen and plasminogen levels of the infusion of a high (1,200,000 units) and medium (250,000 units) standardized initial dose of streptokinase. In both groups the administration of the initial dose was followed by a continuous infusion of 100,000 units of streptokinase per hour. Immediately after the initial dose of 1,200,000 units of streptokinase, the plasma plasminogen was already below 1% of the normal value in half the patients. No significant further change in the distribution was found in samples withdrawn after 24 hours of maintenance therapy; at that time the plasma plasminogen concentration was below 1% of the normal value in 48% of the patients and below 5% of the normal value in 93% of the patients. Immediately after the initial dose of 250,000 units of streptokinase the plasma plasminogen level was below 1 % of the normal value in only 13% of the patients. Nevertheless, after 24 hours of maintenance therapy, the plasminogen level had reached values which were practically identical to those observed following the high initial dose; in 55% of the patients the plasma plasminogen level was less than 1 % and in 86% of the patients less than 5% of the normal value. The changes of the fibrinogen levels, as observed with the fibrin polymerization time test, also showed some interesting differences. When 1,200,000 units of streptokinase were given as the initial dose, there was a very marked drop of the fibrinogen level but after 24 hours' maintenance therapy there was a significant increase. When 200,000 units of streptokinase were infused there was a smaller immediate fall of the fibrinogen level but after 24 hours' maintenance therapy it had decreased still further. It should be emphasized that the biological fibrinogen assay used in this study is influenced not only by the actual fibrinogen level but also by the presence of those fibrinogen degradation products which interfere with polymerization.