Pulmonary thromboembolism. 2. New trends in prophylaxis and therapy.

Although low-dose heparin therapy is the technique most commonly used for prophylaxis of pulmonary thromboembolism, its usefulness is being questioned. Platelet deaggregation prophylaxis with either aspirin or dipyridamole, or both, apparently is a reasonable alternative, but further studies are needed. For treatment of pulmonary thromboembolism, continuous conventional-dose heparin therapy is the approach of choice. It has the highest therapeutic/toxic ratio and is the most effective technique for prevention of clot propagation. The patient's fibrinolytic network must be intact, however, if clot degradation is to occur. Fibrinolytic therapy with urokinase or streptokinase should be restricted to use in patients with massive pulmonary embolism in whom hemodynamics are unstable. Caval interruption and pulmonary embolectomy have lower benefit/risk ratios than do the medical alternatives and are rarely used for pulmonary thromboembolism.