See related articles: Thrombophilia, Pulmonary Embolism, Deep Vein Thrombosis

Clinicians are frequently asked to advise patients on prophylactic measures to minimise the risk of venous thrombo-embolism (VTE). The National Institute for Health and Clinical Excellence (NICE) has produced guidelines to assist in reducing the risk.¹

• NICE states that approximately 30% of surgical patients develop DVT.
• The condition is frequently asymptomatic but can lead to sudden death due to pulmonary embolism (PE).
• The risk of fatal embolism after high-risk surgery is 1-5%.

The following surgical procedures are high-risk:

• Orthopaedic surgery (for example, total surgery for hip fracture).
• Major general surgery.
• Major gynaecological surgery (but not Caesarean).
• Urological surgery (including major or open urological procedures).
• Neurosurgery.
• Cardiothoracic surgery.
• Major peripheral vascular surgery.

Assessing the risk¹

Patients should be assessed individually, both considering any existing risk factors for VTE, and their risk of bleeding (i.e may be already at lower risk of DVT). A decision can then be made whether VTE prevention should be offered and, if so, whether this should be pharmacological or mechanical. For patients with increased risk, the balance of risk versus benefits of treatment should be reassessed at regular intervals. For patients in hospital this should be 24 hours after admission or whenever there is a change in the clinical situation.

National Institute for Health and Clinical Excellence (2010) CG 92 Venous thromboembolism: reducing the risk. London: NICE. Available from www.nice.org.uk/CG92 Reproduced with permission.

Management¹

All patients

• Avoid dehydration unless there is a specific clinical reason.
• Encourage early mobilisation.
• Aspirin or antiplatelet agents should not be considered adequate prophylaxis.
• Consider temporary inferior vena cava filters for patients at a very high risk of VTE (e.g. active malignancy or previous VTE event) if there are contra-indications to pharmacological and mechanical prophylaxis. These are devices which can be inserted into the inferior vena cava to prevent the development of a pulmonary embolus.

Choice of prophylaxis

Mechanical

Several methods are available:

• Graduated compression stockings are effective in decreasing the risk of DVT, either alone or in combination with pharmacological prophylaxis in high-risk patients. Thigh-length graduated compression/anti-embolism stockings can be used unless contra-indicated (e.g. in patients with established peripheral arterial disease or diabetic neuropathy). Graduated compression stockings should be used routinely for surgical inpatients. If thigh-length stockings are not appropriate (for reasons of fit or compliance) knee-length stockings may be used instead.²
  • The stocking compression profile should be equivalent to the Sigel profile (a pressure profile for elastic stockings) and approximately:
    • 18 mm Hg at the ankle
    • 14 mm Hg at the mid-calf
    • 8 mm Hg at the upper thigh
• Staff trained in the use of compression stockings should show the patient how to wear them correctly, monitor their use and provide assistance when needed.
• Patients should be encouraged to wear stockings from admission until they return to their normal level of mobility.
• Intermittent pneumatic compression or foot impulse devices may be used instead of, or as well as, graduated compression stockings while patients are in hospital. They should be used for as long as practical prior to surgery.

• Fondaparinux sodium.
• Low molecular weight heparin (LMWH4) - synthetic alternatives may be more acceptable to patients who want a non-animal based product.
• Unfractionated heparin (UFH) (for patients with renal failure).

Start pharmacological VTE prophylaxis as soon as possible after risk assessment.

Specific clinical scenarios

Patients having elective surgery

• Oral contraceptives or hormone replacement therapy (HRT) containing oestrogen should be stopped 4 weeks before surgery.
• For patients on antiplatelet therapy, balance the risks versus benefits of stopping one week before surgery (involve other clinical colleagues as necessary).
• Regional anaesthesia carries less risk than general; consider the patient's wishes, suitability and any other planned methods of VTE prophylaxis.
• If using regional anaesthesia consider timing of pharmacological prophylaxis to minimise risk of epidural haematoma; refer to standard product characteristics for the optimum timing of antiplatelet or anticoagulant prophylaxis with regard to regional anaesthesia.
• Prophylaxis is unnecessary in patients having local anaesthesia by local infiltration if there is no restriction in mobility

• Signs and symptoms of DVT and PE.
• Correct use of prophylaxis at home.
• Implications of not using prophylaxis correctly.

• Offer prophylaxis (pharmacological or mechanical) if the risk of thrombosis outweighs the risk of bleeding.
• Prophylaxis should not be offered to patients taking vitamin K agonists who are within therapeutic range, providing anticoagulant therapy is continued.
• Patients on full anticoagulant therapy should not be offered additional prophylaxis - pharmacological or mechanical.

• Anti-embolism stockings should not be offered.
• If risk factors suggest high risk of VTE (e.g. significant restriction to mobility, previous history of VTE, malignancy) and haemorrhagic stroke has been excluded, consider LMWH or UFH.
• If there is low risk of VTE, reassess in 24 hours.
• If risk of bleeding is low, offer foot impulse or an intermittent pneumatic compression device. Consider also as interim intervention whilst awaiting results of investigations.

• Pre-pregnancy counselling and a management plan should be offered to all women who are at high risk of VTE.
• All pregnant women should have their risk factors assessed and documented.
• This assessment should be repeated if there is a hospital admission for any reason or if complications develop.
• Thrombophilia should be excluded in women with a previous non oestrogen-related VTE which has been provoked by a minor risk factor.
• Prophylaxis should begin as soon as possible in pregnancy.
• LMWH is the prophylaxis of choice, being safer and equally effective as UFH.
• Any woman with three or more persistent or recurrent risk factors identified in Table 1 should be considered for antenatal prophylaxis.
• LMWH should not be given routinely to women who have had one previous VTE event providing this is non oestrogen-related and they have no other risk factors but they should be monitored closely.
• Women should be offered prophylaxis antenatally if:
  • They have a history of recurrent DVT
  • An unprovoked, oestrogen-related or pregnancy-related VTE
  • A previous VTE and a first-degree relative with a history of DVT or proven diagnosis of thrombophilia
• Women with asymptomatic inherited or acquired thrombophilia should be monitored closely antenatally but should be referred to a local expert if:
  • They have antithrombin deficiency
  • The have more than one thrombophilic defect (including homozygosity for factor V Leiden)
  • Those with additional risk factors
• Women given LMWH should be warned that if they have vaginal bleeding or go into labour they should not have any more LMWH injections.
• After delivery:
  • Women should be assessed for the risk factors in Table 2
  • Mobilisation should be encouraged during and after labour
  • Fluid intake should be encouraged
  • Women with two or more risk-persisting risk factors as per Table 2 should be considered for LMWH for 7 days postnatally.
  • Women with three or more such factors should be given graduated compression stockings as well as LMWH
  • Women with BMI>40kg/m² should be considered for LMWH prophylaxis for seven days postnatally
  • GPs may find that women who have had an emergency or elective Caesarean section are discharged on LMWH. The decision to initiate this and the duration of treatment will depend on what risk factors are present (e.g. age, weight, comorbidities, family history of thrombophilia)
  • Women who have had a VTE before the current pregnancy should be considered for LMWH for six weeks postnatally. If they are receiving LMWH before pregnancy, preventative doses of LMWH should be given until 6 weeks postpartum. A postnatal risk assessment should then be made. Patients on long-term warfarin can recommence this when the risk of haemorrhage is low
  • Breast-feeding is no contra-indication to either warfarin or LMWH
  • Repeated risk assessments for VTE should be carried out if women develop intercurrent problems, or they require surgery or readmission for any reason in the puerperium
  • For women with additional risk factors lasting more than 7 days postpartum - e.g. wound infection, prolonged admission - thromboprophylaxis should be continued for up to six weeks or until the risk factors have resolved

© Royal College of Obstetricians and Gynaecologists; reproduced with permission."

© Royal College of Obstetricians and Gynaecologists; reproduced with permission.

High-risk patients

High-risk patients (e.g. multiple risk factors especially previous DVT/PE) should be offered:

• Mechanical prophylaxis
  Several methods are available:
  • Graduated compression stockings are effective in decreasing the risk of DVT, either alone or in combination with pharmacological prophylaxis in high-risk patients. Thigh-length graduated compression/anti-embolism stockings can be used unless contra-indicated (e.g. in patients with established peripheral arterial disease or diabetic neuropathy). Graduated compression stockings should be used routinely for surgical inpatients. If thigh-length stockings are not appropriate (for reasons of fit or compliance) knee-length stockings may be used instead.²
    • The stocking compression profile should be equivalent to the Sigel profile (a pressure profile for elastic stockings) and approximately:
    • 18 mm Hg at the ankle
    • 14 mm Hg at the mid-calf
    • 8 mm Hg at the upper thigh
  • Staff trained in the use of compression stockings should show the patient how to wear them correctly, monitor their use and provide assistance when needed.
  • Patients should be encouraged to wear stockings from admission until they return to their normal level of mobility.
  • Intermittent pneumatic compression or foot impulse devices may be used instead of, or as well as, graduated compression stockings while patients are in hospital. They should be used for as long as practical prior to surgery.
• Pharmacological prophylaxis
  • Patients with high risk and those having orthopaedic surgery should also be offered LMWH. Fondaparinux, within its licensed indications, is an effective and safe alternative.⁴
  • Two new agents, dabigatran and rivaroxaban, have recently been licensed for use in orthopaedic thromboprophylaxis.⁵
  • Consideration should be given to the risks and benefits of stopping pre-existing anticoagulation or antiplatelet therapy before surgery.
  • Pharmacological prophylaxis may need to be stopped if regional anaesthesia is employed to minimise the risk of haematoma (the timing depending on the type of anticoagulant and the type of procedure).⁶
• Other options
  • Patients should be encouraged to maintain their fluid intake and not become dehydrated during their stay in hospital.
  • Regional anaesthesia is to be preferred if possible as it is less of a risk for VTE than general anaesthesia.
  • Vena cava filters should be considered for patients who have existing or recent (within one month) VTE and anticoagulation therapy is contra-indicated. These are devices which can be inserted into the inferior vena cava to prevent the development of a PE.
  • Patients should be encouraged to mobilise, or leg exercises should be arranged if they are immobile, as soon as possible after surgery.

Patients with no risk factors

Patients having hip replacement, surgical treatment of hip fractures and other kinds of major orthopaedic surgery should be offered mechanical and pharmacological prophylaxis. Otherwise, only mechanical prophylaxis is required.

Travel-related DVT

At the time of writing, NICE guidance on the prevention of travel-related DVT and other nonsurgical scenarios is being developed. In the interim, clinicians should advise patients according to the guidance produced by the Department of Health (DH).⁷ The DH states that DVT or PE occur every year in about 1-3 in 1,000 people in the general population, ranging from less than 1 in 3,000 in people under the age of 40 up to 1 in a few hundred in those aged over 80. 90-95% of travel-related DVT or PE occur in the following groups:

• Over 40 years of age
• Pre-existing thrombosis
• A family history of thrombosis
• Suffering from, or who have had treatment for, cancer
• With hypercoagulable blood disorders, e.g. thrombophilia
• Co-existing heart failure and circulation problems
• Recent surgery, especially on the hips or knees
• The very tall

DVT is also more common in women who:

• Are pregnant
• Have recently had a baby
• Are taking the contraceptive pill
• Are on HRT

During the trip, the DH recommends advising passengers to:

• Get comfortable and recline the seat as much as possible
• Wear loose-fitting clothing
• Store hand luggage in the overhead lockers to keep the room under the seat in front free
• While seated, bend and straighten the legs, feet and toes every half-hour or so during the flight
• Press the balls of the feet down hard against the floor or footrest to increase the blood flow in the legs and reduce clotting
• Do upper body and breathing exercises to improve circulation further
• Take occasional short walks around the cabin, whilst the aircraft is cruising at altitude
• Take advantage of refuelling stopovers where it may be possible to get off the plane and walk about
• Drink a reasonable amount of water
• Avoid alcohol, which in excess leads to dehydration and immobility
• Avoid taking sleeping pills, which also cause inertia

• For people at moderate risk (e.g. women on HRT or the Pill, past history of VTE), consider using compression hosiery
• For people at high risk (e.g. travel-related VTE in the past 5 years, spontaneous VTE in the past 5 years, any VTE in the past 1 year), in addition to stockings, seek the advice of a haematologist. Consider a single dose of LMWH injection 2-3 hours prior to departure and again prior to returning home
• There is no evidence that addition of aspirin, or increasing existing aspirin dose, has a preventative effect in any high-risk group

Document references

1. Venous thromboembolism - reducing the risk, NICE Clinical Guideline (January 2010); Reducing the risk of venous thromboembolism (deep vein thrombosis and pulmonary embolism) in patients admitted to hospital
2. Phillips SM, Gallagher M, Buchan H; Use graduated compression stockings postoperatively to prevent deep vein thrombosis. BMJ. 2008 Apr 26;336(7650):943-4.
3. Reducing the Risk of Thrombosis and Embolism during Pregnancy and the Puerperium, Royal College of Obstetricians and Gynaecologists (November 2009)
4. McRae SJ, Eikelboom JW; Latest medical treatment strategies for venous thromboembolism. Expert Opin Pharmacother. 2007 Jun;8(9):1221 [abstract]
5. Roberts LN, Arya R; New Anticoagulants for Prevention and Treatment of Venous Thromboembolism. Curr Vasc Pharmacol. 2010 Jan 1. [abstract]
6. Horlocker T, Benzel D, Wedel H et al; Regional Anesthesia in the Anticoagulated Patient: Defining the Risks (The Second ASRA Consensus Conference on Neuraxial Anesthesia and Anticoagulation) Regional Anesthesia and Pain Medicine Vol. 28 No. 3 May–June 2003
7. Advice on travel-related DVT; Department of Health 2007
8. Deep vein thrombosis, Clinical Knowledge Summaries (April 2009)

Acknowledgements