The prevention of deep vein thrombosis and pulmonary embolism.

The development of the 125I-fibrinogen technic in the diagnosis of postoperative deep vein thrombosis provides a valuable tool for the study of the condition itself and of the efficacy of prophylactic measures. These measures may be divided into two groups: the antistasis regimes and the antithrombotic regimes. Published reports based on the 125I-fibrinogen technic are critically reviewed. Although many regimes cause a significant diminution in the incidence of isotopically detected deep vein thrombosis, 90 per cent of which are confined to the calf, this does not necessarily imply a similar diminution in the incidence of major pulmonary emboli, most of which arise from thrombi in the proximal segment of the lower limb veins. The origin of these proximal thrombi, with particular reference to their relationship to calf thrombi, is discussed. The reported studies of the influence of antithrombotic regimes on the incidence of pulmonary embolism are reviewed. It is concluded that a reduction in the incidence of isotopically detected deep vein thrombosis is probably accompanied by a significant reduction in the incidence of major pulmonary embolism, but further studies are required.