How to prevent deep vein thrombosis of the lower extremities?

Patients at low risk for deep vein thrombosis (eg, those who have had minor surgery but have no clinical risk factors for deep vein thrombosis; or those who must be temporarily restrained for an extended period, such as during an airplane flight) should walk or perform intermittent leg movements. Flexing the legs 10 times per hour appears to be sufficient. No treatment is necessary.

Patients at higher risk of deep vein thrombosis (eg, those who have had minor surgery but have clinical risk factors for deep vein thrombosis; those who have had major surgery, especially orthopaedic surgery, even without risk factors; those who are bedridden) require additional prophylaxis. Such patients should be identified and treated before a clot forms. After surgery, leg elevation and avoidance of sitting in chairs (which impedes venous return by forcing the legs into a position) are effective. Additional treatment may include low-dose UFH, LMWH, warfarin, newer anticoagulants, compression devices or stockings, or a combination of these measures, depending on the level of risk, type of surgery, anticipated duration of prophylaxis, contraindications, adverse effects, relative cost, ease of use, and local practice.

Low-dose UFH (5,000 IU) is administered subcutaneously 2 hours before surgery and every 8-12 hours thereafter for 7-10 days or until the patient is discharged to outpatient care. Bedridden patients who have not undergone surgery are given 5,000 IU subcutaneously every 12 hours indefinitely (or until risk factors have completely disappeared).

LMWH is more effective than low-dose UFH in preventing deep vein thrombosis and pulmonary embolism, but widespread use is limited by cost. Enoxaparin sodium 30 mg subcutaneously every 12 hours, dalteparin sodium 2,500 IU once daily, and tinzaparin 3,500 IU once daily are equally effective.

Warfarin 2-5 mg once daily or in a dose adjusted based on INR control (at 1.5-2) is usually prescribed, but the efficacy and safety have not been proven.

Newer anticoagulants (eg, hirudin, ximelagatran, danaparoid, fondaparinox) are effective in preventing deep vein thrombosis and pulmonary embolism, but their cost-effectiveness and safety compared with sodium heparin and warfarin require further study. The efficacy of aspirin is greater than placebo but less than all other available drugs in preventing deep vein thrombosis and pulmonary embolism.

Intermittent pneumatic compression (IPC) involves using a pump to cyclically inflate and deflate hollow plastic gaiters, providing external compression of the calves and sometimes thighs. IPC may be used instead of or in addition to anticoagulants before and during surgery. IPC is more effective in preventing calf DVT than proximal DVT, so it is considered ineffective after hip or knee surgery. IPC is generally contraindicated in the obese and may theoretically cause pulmonary embolism in immobilized patients who develop silent DVT without prophylaxis.

The effectiveness of distributed pressure compression stockings is questionable except in patients at low surgical risk. However, combining the use of stockings with other preventive measures may be more effective than either measure alone.

In surgeries or conditions with a high incidence of venous thromboembolism (eg, orthopaedic, some neurosurgeries, spinal cord injury, multiple trauma), neither low-dose UFH nor aspirin is of benefit. In orthopaedic hip and lower extremity surgeries, LMWH or warfarin in an individually adjusted dose are recommended. In knee replacement, LMWH and IPC have comparable efficacy and should be used in combination if clinical risk factors are present. In orthopaedic surgery, prophylaxis is initiated preoperatively and continued for at least 7 days postoperatively. In neurosurgical patients, physical measures (IPC, compression stockings) are suggested because of the risk of intracerebral hemorrhage; however, LMWH may be an acceptable alternative. The combination of IPC and LMWH is sometimes more effective than either intervention alone in at-risk patients. Limited research supports the combination of IPC, compression stockings, and LMWH in patients with spinal cord injury or multiple trauma.

For patients with a very high risk of venous thromboembolism, bleeding and taking anticoagulants, the installation of an NVC becomes the treatment of choice.

Prophylactic treatment of deep vein thrombosis of the lower extremities is also prescribed for patients who have had an acute myocardial infarction or ischemic stroke. Low-dose UFH is effective in patients who are no longer receiving intravenous heparin or thrombolytic agents. IPC, compression stockings, or a combination of both can be used when there are contraindications to the use of anticoagulants. After stroke, low-dose UFH or LMWH is used; IPC, elastic stockings, or a combination of both may also be useful. Other recommendations include low-dose UFH for patients with heart failure, warfarin in an individually adjusted dose (INR 1.3-1.9) for patients with metastatic breast cancer, and warfarin 1 mg once daily for cancer patients with a central venous catheter.

Primary prevention of venous insufficiency and postphlebitic syndrome is wearing knee-length compression stockings that provide a pressure of 30-40 mm Hg.

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