Venous thromboembolism

VTE (deep vein thrombosis or pulmonary embolism) can occur as a result of long periods of immobility associated with any form of travel Venous thromboembolism

 

Key Messages

Venous thromboembolism (deep vein thrombosisor pulmonary embolism) can occur as a result of long periods of immobility associated with any form of travel.
The risk of venous thromboembolism (VTE) for most travellers is low. For a flight > 4 hours, in healthy individuals, the risk is estimated to be 1 in 6,000. The risk increases with longer duration of travel and with multiple flights within a short period.The risk of pulmonary embolism is much lower.
Some travellers are at increased risk e.g. older travellers, pregnant women, those with a previous history of VTE or recent surgery, those with certain blood clotting disorders, malignancy, certain heart conditions and those taking oestrogen containing medicines (see risk for travellers section).
To reduce the risk of VTE, travellers should regularly mobilise their legs (walk when possible or flex and extend the ankles to encourage blood flow from the lower legs).
Those at increased risk of VTE should seek advice from their health care provider and consider the use of properly fitted compression socks. Low molecular weight heparin therapy may also be recommended.

Overview

Venous thromboembolism (VTE) is term used to cover a spectrum of diseases from deep vein thrombosis (DVT)to pulmonary embolism (PE). VTE is the result of a blood clot (a thrombus) forming in a deep vein, usually in the lower leg.

Long periods of immobility can slow the blood flow from the lower legs which can result in pooling and coagulation(clotting). Reduced blood flow can be further compounded by pressure on the popliteal vein in the back of the knee, such as that caused by aseat during prolonged travel. A clot developing in the vein can occlude (block) the blood vessel and cause swelling of the affected limb.

A pulmonary embolus is caused by the blood clot dislodging from the vein and travelling to the lungs. This is a serious complication and can be life threatening [1].

VTE can occur as a result of periods of immobility, for example following surgery, but can also occur spontaneously in otherwise healthy persons.

VTE has been known to occur following long haul air travel and has been called ‘economy class syndrome’; however this term is misleading as VTE has also been reported following car and train journeys. The preferred term is now travel related VTE or travellers’ thrombosis.

Risk for travellers

The risk of VTE related to long periods of immobility has been known for many years [2, 3].

Studies from the World Health Organization Research into Global Hazards of Travel (WRIGHT) project on air travel and venous thromboembolism indicates that the risk of VTE approximately doubles after a long–haul flight (>4 hours) and also with other forms of travel where travellers are seated and immobile. The absolute risk of VTE for a flight > 4 hours, in healthy individuals, is estimated to be 1 in 6,000. The risk for travellers increases with the duration of the travel and with multiple flights within a short period [4].

In addition, particular risk factors for healthy young (mean age 35-40 years) travellers identified in the WRIGHT studies are:

  • obesity
  • extremes of height
  • use of oestrogen containing oral contraceptives
  • presence of prothombotic blood abnormalities (conditions where the blood is more prone to form clots) [3].
  • Several factors that increase the risk of VTE have been identified [5-7]. These include:
  • history of DVT or PE
  • haematological hypercoaguable disorders (conditions where the blood is more prone to form clots e.g. Factor V Leiden deficiency, thrombocythaemia, antithrombin deficiency)
  • pregnancy and women who have had a baby in the last 6 weeks
  • malignancy (active cancer)
  • congestive cardiac failure or recent myocardial infarction (heart attack)
  • recent surgery of more than30 minutes duration, performed 4 weeks to 2 months ago
  • oestrogen therapy (e.g. oral contraceptive pill and hormone replacement therapy)
  • older age (over 60 years)
  • recent serious injury / trauma

The most severe form of VTE is pulmonary embolism. This has been estimated to occur in approximately 5 cases per million flights > 12 hours [8].

Signs and symptoms

A VTE can be asymptomatic (without symptoms), however, some persons may develop pain in the calf accompanied by swelling and redness. If the vein is completely occluded there may be a blue discoloration of the limb and severe oedema(swelling).

Pulmonary embolus (PE) is a serious complication and can be life threatening; sudden onset of dyspnoea (shortness of breath) is the most common clinical feature.

Diagnosis and treatment

A blood test (D-dimer) can be used to look for fragments of a blood clot in the blood stream. Ultrasound scans can also be used to detect clots in the deep veins of the leg. Guidance on diagnosis and management of DVT and PE are available from the National Institute for Health and Care Excellence (NICE) [9].

Once a VTE has been identified anticoagulation treatment with heparin and an oral anticoagulant such as warfarin is usually commenced. Anticoagulation therapy is usually continued for between 3-6 months, and patients are advised to wear a compression stocking on the affected limb for a period of time.

Preventing VTE

There are a number of measures that can be taken to reduce the risk of travel related VTE. All travellers intending to take long haul flights or other forms of travel where they will be seated or immobile for >4 hours should:

  • walk around the cabin as much as is practical at regular intervals during the flight
  • regularly flex and extend the ankles which will encourage blood flow from the lower legs
  • avoid stowing hand luggage under the seat as it restricts movement
  • avoid wearing constrictive clothing around the waist or lower extremities

Compression socks

Travellers at an increased risk of VTE are advised to consider the use of properly fitted below knee graduated compression socksproviding 15 to 30mmHg of pressure at the ankle. These socksreduce the risk of symptomatic VTE [10,11] and also reduce swelling associated with long haul flights [12, 13]. Furthermore, it has been shown that the risk of asymptomatic VTE is reduced in travellers using compression socks [4]. Pregnant travellers on flights >4 hours should have graduated compression socks fitted [11, 13]. It is important for all travellers that compression stockings are correctly measured and fit properly as poorly fitted socks could further increase the risk of VTE.

Low molecular weight heparin (LMWH)

The value of LMWH in the prevention of VTE in persons at higher risk of VTE is well established. However, its use in the prevention of travel related VTE is less clear. Most medical practitioners recommend the use of LMWH for travellers at high risk of developing VTE, for example a history of previous VTE or pulmonary embolus [8]. Pregnant travellers with additional risk factors may be advised to have LMWH whatever the duration of the flight [14, 15]. A suitable regimen of LMWH should be discussed with a haematologist, and the traveller or companion trained in its administration unless currently anticoagulated with oral medication such as warfarin.

Aspirin

There is good evidence that aspirin is useful in preventing arterial thrombosis, but it is not recommended for the prevention of venous thrombosis during travel. Aspirin does not reduce VTE in high risk patients [11, 16]. Furthermore a Cochrane review noted that approximately one patient in 40 taking low dose aspirin develop gastric irritation [17].

Due to insufficient evidence supporting the use of aspirin in travel related venous thrombosis, guidelines from the American College of Chest Physicians recommend against its use for VTE prevention associated with travel [6]. UK guidelines support the view that aspirin should not be used for the prevention of VTE in travellers [8].

First Published :   01 Jan 2014
Last Updated :   20 Apr 2016

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  2. Ferrai E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk factor for venous thromboembolic disease: a case control study. Chest 1999; 115: 440-44
  3. Cannegieter SC, Doggen CJM, van Houwelingen HC, Rosendaal FR. Travel-related venous thrombosis: Results from a large population-based case control study (MEGA study). PLoS Med. 2006; 3: 1258-1265.
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  9. National Institute for Health and Clinical Excellence (NICE), Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing [Accessed 3 February 2015] 
  10. Hopewell S, Juszczak E, EisingaA,et al. Compression stockings for preventing deep vein thrombosis in airline passengers. Cochrane Database Syst Rev 2006; CD004002
  11. Kahn SR, Lim W, Dunn AS et al. Prevention of VTE in Nonsurgical Patients. Chest 2012; 141(Suppl 2):195–226
  12. Scurr JH, Machin SJ, Bailey-King S et al. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. Lancet 2001; 357: 1485-89
  13. Belcaro G, Cesarone M, Shah S et al. Prevention of edema, flight microangiopathy and venous thrombosis in long flights with elastic stockings. A randomized trial. Angiology 2002; 53: 635-645
  14. Royal College of Obstetricians and Gynaecologists.Air Travel and Pregnancy.Scientific Impact Paper No.1. May 2013 [Accessed 21 January 2015]
  15. Royal College of Obstetricians and Gynaecologists.Air Travel and Pregnancy- Information for you. 2011 [Accessed 29 May 2013]
  16. Cesarone MR, Belcaro G, Nicolaides AN et al. Venous thrombosis from air travel: the LONFLIT3 study- prevention with aspirin vs low molecular weight heparin (LMWH) in high-risk subjects: a randomized trial. Angiology. 2002; 53(1):1-6
  17. Edwards JE, Oldman A, Smith L et al. Single dose oral aspirin for acute pain (Cochrane Review). In The Cochrane Library 2004, Chichester: John Wiley & Sons Ltd

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