Relevance of changes in blood fibrinolytic and coagulation parameters during thrombolytic therapy.

Laboratory tests of blood coagulation and fibrinolytic processes could potentially be used with thrombolytic therapy to detect and monitor the presence of a plasma proteolytic state; to predict bleeding complications, reperfusion, and reocclusion; and to control the patient's clinical course following thrombolysis. However, laboratory measures of the "lytic state" do not correlate well with either thrombolytic efficacy or bleeding complications. The development of fibrin-specific agents and the technique of regional perfusion of thrombolytic drugs represent efforts to reduce systemic fibrinolytic effects and hence decrease bleeding complications. Fibrin-specific agents are not safer with regard to hemorrhagic problems, however, and data as to their increased thrombolytic efficacy are equivocal. Regional perfusion still produces some systemic effects. The probable reason for the lack of predictability of laboratory data for clinical outcome is that both pathologic thrombi and hemostatic plugs have a wide range of susceptibility to fibrinolytic agents. Clot features that influence sensitivity to thrombolysis include age of the thrombus, molecular structure of the clot and the contribution of platelets, and location of the clot within the vascular system. Although the concept of controlling short-term thrombolysis or bleeding complications by laboratory monitoring and regulation of blood coagulation is inconsistent with clinical experience gained to date, the laboratory is useful to prove a "lytic" state in prolonged infusions, to monitor heparin administration, and to evaluate patients for possible surgical intervention.