Click here to view next page of this article
Prevention of deep venous thrombosis is the most effective approach to the problem of pulmonary embolism. Elevation of the lower extremities for gravity drainage of venous return has been shown experimentally to stop venous pooling in the lower extremities. Elevation of the legs with flexion of the knee causes rapid runoff of the blood in the veins of the leg.
Sequential compression of the legs by pneumatic boots and prophylactic anticoagulation have been shown to be useful, but both. Some patients benefit from prophylactic anticoagulation, especially those who experienced trauma or orthopedic disorders, including fracture of the hip.
Low-molecular-weight heparins (LMWHs) are fragments of commercial-grade standard heparin produced by enzymatic or chemical depolarization, which leads to a more homogeneous population of molecules with mean molecular weights.
The management of documented venous thrombosis and pulmonary embolism is primarily by anticoagulant therapy. Heparin should be administered intravenously by constant infusion. Continuous intravenous infusion provides a more stable level of anticoagulation.
Much effort has been directed toward defining the appropriate use of thrombolytic agents in the treatment of venous thrombosis and pulmonary embolism. Plasminogen is the inactive precursor of plasmin, the active fibrinolytic enzyme. Normally, plasminogen is present in the blood and tissues, and exercise, stress, and shock cause plasminogen to be activated to plasmin.
To determine the long-term effects of thrombolytic treatment of acute massive embolism, seven patients with this problem underwent pulmonary angiography with pressure measurements before and after treatment with intrapulmonary infusion of UK (average dose 1724 units per kg. per hour).
The role of SK therapy in the routine management of deep venous thrombosis in the lower extremities was evaluated in a retrospective study of phlebographic results and therapeutic complications. Among 108 patients with phlebographically verified deep venous thrombosis treated with SK, total or partial thrombolysis was demonstrated angiographically in 60 (55.6%). However, three died during treatment.
Although anticoagulant therapy for pulmonary embolism is most often successful, and lytic therapy is finding an accepted role in the management of patients with hemodynamic compromise.
Although the direct removal of venous thrombi was previously recommended, it is now rarely done because of the high incidence of recurrent thrombosis postoperatively. One rare indication for thrombectomy.
Surgical interruption of the vena cava was previously recommended for selected patients with pulmonary embolism but is seldom done today. Moreover, it does not necessarily prevent subsequent embolism, since evidence of recurrent pulmonary embolism is reported.
Several procedures designed to simplify caval interruption have been developed, with an emphasis on reducing perioperative morbidity and mortality. One device is a filter designed to trap large emboli arising from the branches of the inferior vena cava. A cone-shaped stainless-steel umbrella that causes minimal reduction in venous flow has been designed by Greenfield and Michna [17] and can be inserted under local anesthesia through the femoral or jugular vein. Fixation of the filter is achieved by hooks that grasp the wall of the inferior vena cava.
In 1908, Trendelenburg performed the first pulmonary embolectomy and described three patients.