Acute arterial obstruction must be relieved immediately to prevent gangrene. Obstruction in major vessels can be relieved surgically; however, distal thrombus propagation obstructs circulation. Small arterial thrombosis is resistant to current therapy, namely, anticoagulants to limit thrombosis and more recently enzymatic lysis of the clot.37,49
Streptokinase,3,22,32,48,49 plasmin ( fibrinolysin),6,13,14,49,61 and chymotrypsin34,48,49 have been used to lyse intravascular thrombi. Objective evidence that thrombi are lysed and that clinical improvement follows is frequently lacking. The thrombolytic ability of enzymes decreases after three days as the aging clot is covered with endothelium and organizes.3,6,49 In very fresh thrombi lysis has been reported in 5 to 20 minutes.3,14,67 Clinically this is rare and fortuitous.
The maximum safe systemic dose must be defined for each enzyme. The range between effective therapy and toxicity may be nil. Immunological phenomenon, fever, chills, hypotension, nausea, vomiting, and abnormalities of the hemopoietic and coagulation