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Deep Venous Thrombosis Prevention

By James D. Douketis, MD, Professor, Divisions of General Internal Medicine, Hematology and Thromboembolism, Department of Medicine; Director, Vascular Medicine Research Program, McMaster University; St. Joseph's Healthcare Hamilton

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DVT prophylaxis begins with

  • Risk assessment

Risk, along with other factors, allow the proper modality to be selected. Preventive measures include

Risk Assessment

Patients at low risk of DVT (eg, those who are undergoing minor surgery but have no clinical risk factors for DVT; those who must be temporarily inactive for long periods, as during an airplane flight) should be encouraged to walk or otherwise move their legs periodically; no medical treatment is needed. Dorsiflexion 10 times/h is probably sufficient.

Patients at higher risk of DVT include those undergoing minor surgery if they have clinical risk factors for DVT; those undergoing major surgery, especially orthopedic surgery, even without risk factors; and bedbound patients with major medical illnesses (eg, most critical care unit patients, other patients with heart failure, COPD, chronic liver disease, stroke). These patients require additional preventive treatment (see Table: Risk of Deep Venous Thrombosis and Pulmonary Embolism in Surgical Patients). Most of these patients can be identified and should receive DVT prophylaxis; in-hospital thrombosis may be responsible for > 50,000 deaths/yr in the US. Hospitalization itself is not considered a risk factor, and hospitalized patients not in one of these categories do not require routine DVT prophylaxis.

Risk of Deep Venous Thrombosis and Pulmonary Embolism in Surgical Patients

Risk Category


Preventive Measures

Risk of DVT/PE (%)




Fatal PE


Nonmajor surgery* in patients < 40 yr with no clinical risk factors

Early and aggressive ambulation






Nonmajor surgery in patients with risk factors

Minor surgery in patients 40–60 yr with no clinical risk factors

Major surgery in patients < 40 yr with no other clinical risk factors

Immobilized patients with major medical illnesses

LDUH q 12 h, LMWH, fondaparinux, or IPC, with or without elastic stockings






Nonmajor surgery in patients > 60 yr or 40–60 with risk factors

Major surgery in patients > 40 yr or with other clinical risk factors

LDUH q 8 h, LMWH, fondaparinux, or IPC





Very high

Major surgery in patients > 40 yr who have had a previous venous thromboembolic, malignant, or hypercoagulability disorder

In patients of any age:

  • Hip or knee arthroplasty

  • Hip fracture surgery

  • Elective neurosurgery

  • Multiple trauma

  • Spinal cord injury

LMWH, oral anticoagulation, IPC, or elastic stockings plus either LDUH q 8 h or LMWH

Fondaparinux if patients have had orthopedic, abdominal, or thoracic surgery or have an acute, severe illness





*Nonmajor surgery is defined here as an operation that does not involve general anesthesia or respiratory assistance.

DVT = deep venous thrombosis; PE = pulmonary embolism; LDUH = low-dose unfractionated heparin; LMWH = low molecular weight heparin; IPC = intermittent pneumatic compression.

Adapted with permission from Geerts WH, Heit JA, Clagett GP, et al: Prevention of venous thromboembolism. Chest119:132S–175S, 2001.


DVT prophylaxis can involve one or more of the following:

  • Mechanical therapy (eg, compression devices or stockings, venous filters)

  • Drug therapy (including low-dose unfractionated heparin, low molecular weight heparins, warfarin, fondaparinux, new oral anticoagulants)

Choice depends on patient’s risk level, type of surgery (if applicable), projected duration of preventive treatment, contraindications, adverse effects, relative cost, ease of use, and local practice.

Mechanical therapy for DVT prophylaxis

After surgery, elevating the legs and avoiding prolonged immobility, which places the legs in a dependent position thereby impeding venous return, can help.

The benefit of graded compression stockings is questionable except for low-risk surgical patients and selected hospitalized medical patients. However, combining stockings with other preventive measures may be more protective than any single approach.

Intermittent pneumatic compression (IPC) uses a pump to cyclically inflate and deflate hollow plastic leggings, providing external compression to the lower legs and sometimes thighs. IPC may be used instead of or in combination with anticoagulants after surgery. IPC is recommended for patients undergoing surgery associated with a high risk of bleeding in whom anticoagulant use may be contraindicated. IPC is probably more effective for preventing calf than proximal DVT. IPC is contraindicated in some obese patients who may be unable to apply the devices properly.

For patients who are at very high risk of venous thromboembolism and bleeding (eg, after major trauma) IPC is recommended until the bleeding risk subsides and anticoagulants can be given. The use of inferior vena cava filters should be avoided unless DVT has been confirmed, except in highly selected patients.

Drug therapy for DVT prophylaxis

Aspirin is better than placebo but likely worse than LMWH and warfarin for preventing DVT and PE and is not recommended as the first-line method of prevention in most patients (see Table: Risk of Deep Venous Thrombosis and Pulmonary Embolism in Surgical Patients).

Low-dose UFH 5000 units sc is given 2 h before surgery and q 8 to 12 h thereafter for 7 to 10 days or until patients are fully ambulatory. Bedbound patients who are not undergoing surgery are given 5000 units sc q 12 h until risk factors are reversed.

LMWHs are more effective than low-dose UFH for preventing DVT and PE, but widespread use is limited by cost. Enoxaparin 30 mg sc q 12 h, dalteparin 5000 units sc once/day, and tinzaparin 4500 units sc once/day appear to be are equally effective. Fondaparinux 2.5 mg sc once/day is at least as effective as LMWH in patients who are undergoing nonorthopedic surgery and is possibly more effective than LMWHs after orthopedic surgery.

Warfarin, using a target INR of 2.0 to 3.0, is proven to be effective in orthopedic surgery but is being used less frequently because alternative anticoagulants such as LMWHs and new oral anticoagulants are easier to administer.

New oral anticoagulants (eg, dabigatran, rivaroxaban, apixaban) are at least as effective and safe as LMWH for preventing DVT and PE after hip or knee replacement surgery but are more expensive than warfarin, and their cost-effectiveness requires further study.

DVT prophylaxis in selected populations

For elective neurosurgery, spinal cord injury, or multiple trauma, low-dose UFH (eg, 5000 units sc q 8 h), LMWH, or adjusted-dose warfarin is recommended. For hip and other lower extremity orthopedic surgery, LMWH, fondaparinux, or adjusted-dose warfarin is recommended. For patients undergoing total knee replacement and some other high-risk patients, IPC is also beneficial. For orthopedic surgery, preventive treatment may be started before or after surgery and continued for at least 14 days. Fondaparinux 2.5 mg sc once/day appears to be more effective to prevent DVT than LMWH for orthopedic surgery but may be associated with an increased risk of bleeding.

For neurosurgery patients, physical measures (IPC, elastic stockings) have been used because intracranial bleeding is a concern; however, LMWH appears to be an acceptable alternative. Limited data support the combination of IPC, elastic stockings, and LMWH in patients with spinal cord injury or multiple trauma.

Preventive treatment is also indicated for patients who have a major medical illnesses requiring bed rest (eg, MI, ischemic stroke, heart failure). Low-dose UFH or LMWH is effective in patients who are not already receiving IV heparin or thrombolytics; IPC, elastic stockings, or both may be used when anticoagulants are contraindicated. After a stroke, low-dose UFH or LMWH can be used; IPC, elastic stockings, or both may be beneficial.

Prevention of postphlebitic syndrome

In patients with symptomatic DVT who develop symptoms of postphlebitic syndrome (eg, leg swelling, pain, aching), the use of knee-high compression stockings providing 30 to 40 mm Hg pressure is recommended, although stockings with lower tension (20 to 30 mm Hg) can be considered if patients are unable to tolerate the higher tension stockings. However, the routine use of stockings in all patients who have had a DVT has been questioned by a recent study which randomly allocated patients with a DVT to receive knee-high compression stockings or sham-compression stockings. This study failed to show any decrease in postphlebitic syndrome with use of compression stockings.

Key Points

  • Preventive treatment is required for bedbound patients with major illness and/or those undergoing certain surgical procedures.

  • Early mobilization, leg elevation, and an anticoagulant are the recommended preventive measures; patients who should not receive anticoagulants may benefit from intermittent pneumatic compression devices, elastic stockings, or both.

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