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Deep Venous Thrombosis (DVT) Prevention


James D. Douketis

, MD, McMaster University

Last full review/revision Feb 2021| Content last modified Feb 2021

It is preferable and safer to prevent deep venous thrombosis (DVT) than to treat it, particularly in high-risk patients. DVT prophylaxis begins with risk assessment. Risk, along with other factors, allows the proper preventive modality to be selected. Preventive measures include

  • Prevention of immobility
  • Anticoagulation (eg, low molecular weight heparin, fondaparinux, adjusted-dose warfarin, direct oral anticoagulant)
  • Intermittent pneumatic compression

Inferior vena cava (IVC) filters do not prevent DVT but are sometimes placed in an attempt to prevent pulmonary embolism (PE). An IVC filter may help prevent PE in patients with lower extremity DVT who have contraindications to anticoagulant therapy or in patients with recurrent DVT (or emboli) despite adequate anticoagulation. Despite widespread use of IVC filters, efficacy in preventing PE is unstudied and unproved.

(See also Deep Venous Thrombosis.)

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 a prolonged [> 6 hour] airplane flight) should be encouraged to walk or otherwise move their legs periodically; no medical treatment is needed. Dorsiflexion 10 times/hour 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, chronic obstructive pulmonary disease [COPD], chronic liver disease, stroke). These patients require additional preventive treatment (see table Risk of Deep Venous Thrombosis and Pulmonary Embolism). Most of these patients can be identified and should receive DVT prophylaxis; in-hospital thrombosis may be responsible for > 50,000 deaths/year 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 year with no clinical risk factors

Early and aggressive ambulation






Nonmajor surgery in patients with risk factors

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

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

Immobilized patients with major medical illnesses

LDUH every 12 hours, LMWH, fondaparinux, or IPC, with or without elastic stockings






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

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

LDUH every 8 hours, LMWH, fondaparinux, or IPC





Very high

Major surgery in patients > 40 years 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 every 8 hours or LMWH

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

LMWH or DOAC in some high-risk patients with cancer undergoing chemotherapy





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

DOAC = direct oral anticoagulant; 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. Chest 119:132S–175S, 2001.

Treatment in DVT Prevention

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, direct 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 DVT 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

Drug prophylaxis involves use of anticoagulants.

Aspirin is better than placebo but likely worse than low molecular weight heparin (LMWH) and warfarin for preventing DVT and PE and is not recommended as the 1st-line method of prevention in most patients (see table Risk of Deep Venous Thrombosis and Pulmonary Embolism).

Low-dose unfractionated heparin (UFH) 5000 units subcutaneously is given 2 hours before surgery and every 8 to 12 hours thereafter for 7 to 10 days or until patients are fully ambulatory. Bedbound patients who are not undergoing surgery are given 5000 units subcutaneously every 12 hours 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 subcutaneously every 12 hours, dalteparin 5000 units subcutaneously once/ a ay, and tinzaparin 4500 units subcutaneously once a day appear to be are equally effective. Fondaparinux 2.5 mg subcutaneously once a 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 international normalized ratio (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.

Direct 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.

With DVT prophylaxis, there is always a risk of bleeding during use of anticoagulants.

DVT prophylaxis in selected populations

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 in whom anticoagulants cannot be given because of a high bleeding risk, 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 subcutaneously once a 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 elective neurosurgery, spinal cord injury, or multiple trauma, low-dose UFH (eg, 5000 units subcutaneously every 8 hours), LMWH, or adjusted-dose warfarin is recommended.

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, myocardial infarction, 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. For select high-risk patients with cancer (eg, advanced pancreatic cancer) who are receiving chemotherapy, primary prophylaxis with LMWH or certain direct oral anticoagulants ( apixaban or rivaroxaban) may be considered (1–4).

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 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.

Treatment references

  • 1. Carrier M, Abou-Nassar K, Mallick R, et al: Apixaban to prevent venous thromboembolism in patients with cancer. N Engl J Med 380:711–719, 2019. doi: 10.1056/NEJMoa1814468
  • 2. Farge D, Frere C, Connors JM, et al: 2019 international clinical practice guidelines for the treatment and prophylaxis of venous thromboembolism in patients with cancer. Lancet Oncol 20 (10): e566–e581, 2019. doi: 10.1016/S1470-2045(19)30336-5
  • 3. Key NS, Khorana AA, Kuderer NM, et al: Venous thromboembolism prophylaxis and treatment in patients with cancer: ASCO Clinical Practice Guideline Update. J Clin Oncol 38:496–520, 2020. doi: 10.1200/JCO.19.01461
  • 4. Khorana AA, Soff GA, Kakkar AK, et al: Rivaroxaban for thromboprophylaxis in high-risk ambulatory patients with cancer. N Engl J Med 380:720–728, 2019. doi: 10.1056/NEJMoa1814630

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 or elastic stockings.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • Farge D, Frere C, Connors JM, et al: 2019 international clinical practice guidelines for the treatment and prophylaxis of venous thromboembolism in patients with cancer. Lancet Oncol 20 (10): e566–e581, 2019. doi: 10.1016/S1470-2045(19)30336-5

Drugs Mentioned In This Article

Drug Name Select Trade
fondaparinux ARIXTRA
rivaroxaban XARELTO
tinzaparin No US brand name
dalteparin FRAGMIN
Enoxaparin LOVENOX
warfarin COUMADIN
apixaban ELIQUIS

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