Primary prevention

Risk stratification

Assess the risk of venous thromboembolism (VTE) and bleeding for any patient admitted to hospital (including those who are admitted as an inpatient or having a day procedure) using a suitable risk assessment tool.[59]

  • Patients who attend hospital but are not admitted (such as those in the emergency or outpatient department) do not require risk assessment, unless they are discharged from hospital with temporary lower-limb immobilisation (e.g., after trauma or orthopaedic surgery).[60]

Check your local protocols and consider the patient’s clinical circumstances when choosing a suitable risk assessment tool. Use this risk assessment to weigh up the risks and benefits of pharmacological prophylaxis.[59]

  • For medical, surgical, and trauma patients:

    • Carry out the risk assessment as soon as possible after admission, or by the time of the first consultant review.[59] Reassess the patient at the consultant review or if their clinical situation changes[59]

    • The National Institute for Health and Care Excellence (NICE) in the UK recommends using the Department of Health VTE risk assessment tool.[59] Department of Health: risk assessment for VTE Opens in new window Other assessment tools include the Caprini RAM, the Geneva Risk Score, IMPROVE-RAM, IMPROVEDD (which includes D-dimer), the Kucher Model, and the Padua Prediction Score.[61][62]

  • For patients who are admitted to hospital or a midwife-led unit who are pregnant or have, within the past 6 weeks, given birth, had a miscarriage, or had a termination of pregnancy:[59]

    • Carry out the risk assessment on admission[59]

    • NICE in the UK recommends using the Royal College of Obstetricians and Gynaecologists risk assessment tool[59] RCOG: VTE risk assessment tool Opens in new window

    • Reassess the patient:

      • Within 6 hours of giving birth, having a miscarriage, or having a termination of pregnancy

      • If their clinical condition changes and they:[59] 

        • Are pregnant

          OR

        • Gave birth, had a miscarriage, or had a termination of pregnancy, within the past 6 weeks.

VTE prophylaxis in hospital

Pharmacological prophylaxis

Use your risk assessment to evaluate the patient’s risk of VTE against their risk of bleeding when deciding whether to give pharmacological thromboprophylaxis.[59]

In general, if pharmacological prophylaxis is indicated in medical, surgical, or trauma patients, start this as soon as possible and definitely within 14 hours of admission, unless there are special considerations for timing (e.g., use of regional anaesthesia, specific types of surgery).[59][60]

  • Take into account your local protocols, any comorbidities (e.g., renal impairment, cancer), and whether the patient is having surgery (and, if so, the type of surgery) when choosing type and dose of pharmacological prophylaxis.[59]

  • Options include low-dose low molecular weight heparin, fondaparinux, and unfractionated heparin.[59] [ Cochrane Clinical Answers logo ] Apixaban, rivaroxaban, dabigatran, and aspirin are also appropriate for pharmacological prophylaxis in patients undergoing joint replacement procedures, along with low molecular weight heparin and fondaparinux.[59][63][64][65][66][67][68][69][70][71][72][73][74] Emerging evidence suggests that apixaban may prevent VTE in intermediate- to high-risk ambulatory patients with cancer; risk of major bleeding with apixaban was, however, greater than with placebo.[75] 

Seek specialist advice if a patient is at high risk of VTE during pregnancy or the postnatal period; there is uncertainty in current evidence about the risks and benefits of pharmacological prophylaxis for these patients.[76]

Mechanical prophylaxis

Consider mechanical prophylaxis (intermittent pneumatic compression or anti-embolism stockings) for patients in hospital who are at increased risk of VTE.[59] Mechanical prophylaxis is particularly useful for patients with a high risk for bleeding or a contraindication to pharmacological prophylaxis. 

  • However, be aware that there is debate in the literature on the use of anti-embolism stockings for prevention of VTE, particularly for patients who have undergone surgery who are already receiving pharmacological prophylaxis.[77]

  • NICE in the UK does not recommend mechanical prophylaxis for certain patient groups, such as medical or obstetric patients.[59]

Choice of anti-embolism stockings versus intermittent pneumatic compression depends on the patient’s acute condition and interventions (e.g., type of surgery), as well as any contraindications.[59] Consult your local protocols, and seek expert advice if you are unsure.

Do not use anti-embolism stockings if the patient has:[59]

  • An acute stroke (intermittent pneumatic compression is preferred)

  • Suspected or known peripheral arterial disease

  • Peripheral arterial bypass grafting

  • Peripheral neuropathy or other causes of sensory impairment

  • A localised condition in which anti-embolism stockings may cause damage (e.g., fragile 'tissue paper' skin, dermatitis, gangrene or recent skin graft)

  • Known allergy to the material of manufacture (this also applies to intermittent pneumatic compression)

  • Severe leg oedema

  • Major limb deformity or unusual leg size or shape that prevents correct stocking fit.

If you are considering anti-embolism stockings and the patient has:[59]

  • Venous ulcers or wounds: use clinical judgment and caution

  • Suspected arterial disease: seek expert advice.

Monitor the patient carefully if they are using anti-embolism stockings.

  • Remove the anti-embolism stockings to inspect the patient's skin condition at least daily.[59] If the patient has a significant reduction in mobility, poor skin integrity, or any sensory loss, inspect their skin condition 2 to 3 times a day, particularly over their heels and bony prominences.[59]

  • Remove the anti-embolism stockings if the patient has marking, blistering, or discoloration of their skin (particularly over their heels and bony prominences) or if they have any pain or discomfort.[59] Consider using intermittent pneumatic compression as an alternative.[59]

Mobilisation and hydration

Encourage patients to mobilise as soon as possible and to ensure they are adequately hydrated.[59]

Extended-duration pharmacological prophylaxis

Consider continued prophylaxis after hospital discharge in certain patient groups, particularly those with lower-limb immobilisation or following major orthopaedic surgery.[59]

More info: Extended-duration pharmacological prophylaxis

Five randomised trials enrolling over 40,000 patients have examined extended-duration prophylaxis following hospitalisation for medical illness.[19][20][21][22][78] Regimens included low molecular weight heparin or oral factor Xa inhibitors at a prophylactic dose for 4 to 6 weeks following discharge. Inclusion criteria varied, but the most common reason for hospitalisation across studies was heart failure. A pooled analysis revealed that extended prophylaxis reduced symptomatic VTE or VTE-related death compared with standard of care (0.8% versus 1.2%; risk ratio [RR] 0.61, 95% CI 0.44 to 0.83; P = 0.002) but increased the risk of major or fatal bleeding (0.6% versus 0.3%; RR 2.04, 95% CI 1.42 to 2.91; P <0.001).[79] Due to the very narrow margin of risks and benefits, further research is needed to appropriately select medical patients for extended prophylaxis following hospital discharge.

Long-distance travel

Do not routinely use pharmacological prophylaxis for patients travelling long distances; instead, consider this on a case-by-case basis (e.g., if the patient has a personal history of VTE).[80] Some evidence suggests that elastic compression stockings may reduce the risk of VTE in these patients.[57] [ Cochrane Clinical Answers logo ] Do not use elastic compression stockings for patients without risk factors; other measures, such as remaining mobile during travel, are preferred.[80]

Secondary prevention

For secondary prevention, if indicated, use extended-duration (beyond 3 months) anticoagulation.[12] Bear in mind that not all patients will need continued anticoagulation beyond 3 months.

Duration of anticoagulation

Discuss with a senior colleague whether to continue anticoagulation beyond 3 months if the patient has a first presentation of a proximal DVT. This decision should assess the individual patient’s risk of recurrence of DVT versus bleeding risk, as well as considering whether the DVT was provoked or unprovoked. Discuss the risks and benefits of long-term anticoagulation with the patient, and take their preferences into account.[12] In UK practice, anticoagulation is rarely continued beyond 3 months if the patient has a distal (calf) DVT, unless they have active cancer. 

  • A provoked DVT is a DVT associated with a major transient risk factor that was present in the 3 months prior to the DVT.[12] 

  • An unprovoked DVT is a DVT in a patient who had no pre-existing, major, transient, provoking risk factor in the prior 3 months.[12] 

  • Major provoking risk factors include: major surgery; trauma; significant immobility (bedbound, unable to walk unaided, or likely to spend a substantial proportion of the day in bed or in a chair); pregnancy or puerperium; use of oral contraceptive/hormone replacement therapy).[12] 

In general, anticoagulation can usually be stopped after 3 months (or 3-6 months for people with active cancer) if the proximal DVT was provoked, as long as the major transient risk factor is no longer present and the clinical course has been uncomplicated.[12] 

  • In the UK, some centres may continue anticoagulation beyond 3 months for patients with a minor transient risk factor (e.g., minor surgery).

Anticoagulation is usually continued for longer than 3 months if the proximal DVT was unprovoked and proximal.[12]

  • In practice, patients with persisting risk factors (e.g., active cancer, autoimmune conditions such as systemic lupus erythematosus and inflammatory bowel disease) usually continue anticoagulation long-term, unless they had a major provoking risk factor (e.g., major surgery). If the patient has active cancer, anticoagulation is continued for at least 6 months.[12] In practice, this will be for at least the duration of cancer treatment, or until remission is achieved. 

Annually reassess the risks/benefits of continuing anticoagulation, as well as the patient's general health and treatment preferences, in all patients receiving extended treatment beyond 3 months.[12][60]

Note that anticoagulants offer secondary prevention benefits only as long as they are continued. There is no legacy effect of a longer time-limited course of treatment; the risk of recurrent venous thromboembolism (VTE) re-emerges as soon as the anticoagulant is discontinued.[162]

Choice of anticoagulant

In general, offer continued treatment with the anticoagulant used in the acute phase if it is well tolerated.[12] 

  • If the patient has been started on a direct oral anticoagulant (DOAC) other than apixaban and this is not well tolerated, or the clinical situation or patient preference has changed, the National Institute for Health and Care Excellence in the UK recommends to consider switching to apixaban if the patient does not have renal impairment, active cancer, established triple-positive antiphospholipid syndrome, or extreme body weight (<50 kg or >120 kg).[12] However, in practice, many patients may prefer an alternative anticoagulant that can be taken as a once-daily regimen. 

  • In patients taking apixaban who need ongoing anticoagulation for >6 months, consider a dose reduction.[122] In UK practice, if the patient is taking rivaroxaban in this scenario, a dose reduction may be considered if there is concern about the risk of bleeding. 

  • In pregnant patients, continue low molecular weight heparin for the remainder of the pregnancy and for at least 6 weeks postnatally and until at least 3 months of treatment has been given in total.[123]

Consider aspirin if the patient declines or is unable to tolerate any form of oral anticoagulant.[12]

More info: Risk of recurrent VTE

Many studies have attempted to identify subgroups of patients with unprovoked VTE who do not need to be treated indefinitely with oral anticoagulation. There is strong evidence that the risk of recurrent VTE is higher in the following patients: male sex; those with a diagnosis of a proximal DVT (versus isolated distal [calf] DVT); those with ultrasound evidence of residual clot; those who have an elevated D-dimer 1 month after stopping a 3- to 6-month course of oral anticoagulation; and those who had an unprovoked DVT.[27][124][125][126][127] Several risk assessment models have been developed for this purpose, including the DASH score, the Vienna Prediction Model, and the 'Men Continue and HER-DOO2' model.[128] The latter model identifies a subset of women with low risk for recurrent VTE after an initial unprovoked event, and a prospective validation study of this model was published.[129] However, these models are not widely used in practice.

Other considerations

If anticoagulation is not continued beyond 3 months, or is interrupted, secondary prevention should also involve episodic VTE prophylaxis when the risk of VTE is elevated.[59]​ For example, during:[12] 

  • Admission to hospital

  • Surgery

  • Pregnancy and the postnatal period

  • Lower-limb immobilisation (e.g., plaster cast).

Other approaches that can also reduce the risk of VTE include:

  • Maintaining a healthy weight

  • Taking regular exercise

  • Avoiding combined hormonal contraception and oral oestrogens

  • Not smoking

  • Using a statin (when indicated for hyperlipidaemia).

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