Deep vein thromboses (DVTs) are extremely common in many groups of hospitalized patients and contribute to patient morbidity and mortality by their propensity to embolize to the lung, where they can lead to severe hypoxemia, increased dead space, respiratory insufficiency, and right-sided heart failure with progression to cardiorespiratory arrest. Many DVTs develop in the deep pelvic veins though a substantial number originate in the deep veins of the thigh. DVTs of the lower leg below the knee are common also but rarely embolize.

Several factors promote the tendency to develop DVTs. Ill patients tend to be hypercoagulable, especially those with certain diseases such as cancer and pancreatitis. This combined with immobility and venous stasis greatly enhances the likelihood of developing clot. Development of clot is a surprisingly rapid event. Patients undergoing surgery have been shown to develop DVTs on the operating table shortly after induction of anesthesia.

Prevention of DVTs or pulmonary embolisms (PEs) is a major concern for hospitalized patients. There are several modalities that are used to prevent this complication; recent evidence suggests that the ones chosen for an individual patient should be based on risk-stratification profiles. These modalities include subcutaneously injected heparin, heparinoids such as enoxaparin, thromboembolic deterrent (TED) stockings, and sequential compression devices (SCDs). While heparin and heparinlike compounds work pharmacologically, TED stockings and SCDs work mechanically by compressing the venous structures in the extremities. The primary mechanism of action for reducing the risk of clot formation is the release of tissue-type plasminogen activator (tPA) from the endothelium in response to the mechanical compression of the veins. The formation of plasmin is enhanced, which presumably promotes the lysis of any clot that is initiated. This is why studies have shown that placing TED stockings or SCDs on the arms of a patient is just as effective as placing them on the legs. Secondarily, the compression of the veins helps to prevent stasis, which is thought to promote clotting.