Thrombolytic therapy.

Thrombolytic therapy, which involves the administration of agents designed to increase fibrinolytic capacity, has been utilized in respiratory medicine for more than 50 years. A variety of agents have been used to effect thrombolysis, including urokinase plasminogen activator (uPA) and streptokinase. Tissue plasminogen activator (tPA) has also been used to effect thrombolysis. Both uPA and tPA are endogenous fibrinolysins that are detectable in plasma and extravascular fluids that accumulate in the setting of inflammation. uPA is the major plasminogen activator present in bronchoalveolar lavage of normal subjects and accounts for the fibrinolytic activity that is detectable in these fluids. These agents are all characterized by a short half-life in plasma, and their effects are mitigated by inhibition attributable to the plasminogen activators, particularly plasminogen activator inhibitor-1, and by downstream antiplasmins. Thrombolytic therapy has been used to clear pathologic fibrin deposition in both extravascular and intravascular compartments. These agents are used to relieve intrapleural loculations associated with complicated parapneumonic pleural effusions and organizing hemothoraces. Thrombolytic therapy has also been used to treat pulmonary embolism associated with hemodynamic compromise. In both instances, the role of thrombolysis in pulmonary medicine continues to evolve based on recent and ongoing investigations.