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How should I assess the risk of travel-related DVT?
- For continuous journeys lasting more than 6 hours, the risk of travel-related deep vein thrombosis (DVT) can be classed as:
- Low risk if the person has:
- No history of DVT or pulmonary embolism (PE), and
- Not undergone surgery in the previous 4 weeks, and
- No other risk factors to indicate moderate or high risk.
- Moderate risk if the person:
- Has a previous history of DVT or PE. However, people with a recent DVT (or PE) who are on anticoagulant treatment are considered to be at low risk.
- Has undergone surgery under general anaesthesia lasting more than 30 minutes in the previous 2 months but not in the last 4 weeks.
- Is pregnant or postpartum.
- Has clinically evident cardiac disease (such as recent myocardial infarction, uncontrolled heart failure) or other major acute illness (such as pneumonia).
- Is taking combined oral contraceptives or hormone replacement therapy.
- Is obese (body mass index greater than 30 kg/m2).
- Has varicose veins with phlebitis.
- Has a family history of venous thromboembolism in a first degree relative.
- Has polycythaemia.
- Has a lower-limb fracture in plaster.
- (The presence of multiple risk factors will further increase the risk of an individual developing travel-related DVT.)
- High risk if the person:
- Has undergone surgery under general anaesthesia lasting more than 30 minutes in the previous 4 weeks.
- Has known thrombophilia.
- Has cancer — untreated or currently on treatment.
- The absolute risk of an individual developing a travel-related DVT remains low even if they are classed as being at relative moderate or high risk.
Basis for recommendation
These recommendations are based on published guidelines, expert reviews, and consensus documents [Kesteven, 2000; SIGN, 2002; Aerospace Medical Association Medical Guidelines Taskforce, 2003; Possick and Barry, 2004; British Committee for Standards in Haematology, 2005; Watson, 2005; Geerts et al, 2008; Sándor, 2008; Schobersberger et al, 2008; Watson and Chee, 2008; Silverman and Gendreau, 2009].
Risk factors
- Although the absolute risk of deep vein thrombosis (DVT) with long-haul flights is very low in healthy individuals without risk factors, there is evidence from the WRIGHT (World Health Organization Research Into Global Hazards of Travel) project and earlier studies that the risk is increased by the presence of risk factors (such as obesity, oral contraceptive use, previous DVT, recent trauma, varicose veins, cardiac disease, thrombophilia, pregnancy and cancer) [Kesteven and Robinson, 2001; Arya et al, 2002; Hughes et al, 2003; Jacobson et al, 2003; Martinelli et al, 2003; Paganin et al, 2003; WHO, 2007].
Duration of travel
How should I advise someone at low risk of travel-related DVT?
- For people assessed as having a relatively low risk of developing travel-related deep vein thrombosis (DVT):
- Provide advice on general measures to reduce the risk of travel-related DVT.
- Reassure the person that no specific treatment is required.
Basis for recommendation
How should I advise someone at moderate risk of travel-related DVT?
- For people assessed as having a relatively moderate risk of developing travel-related deep vein thrombosis (DVT):
- Provide advice on general measures to reduce the risk of travel-related DVT.
- Advise the use of graduated compression stockings.
- Class 1 stockings or proprietary flight socks are generally sufficient.
- Measure the ankle-brachial pressure index (ABPI) if the person has symptoms of arterial disease. If the ABPI is less than 0.5, compression stockings should not be worn.
- For further information, see Compression stockings.
Basis for recommendation
These recommendations are based on published guidelines, expert reviews and consensus documents [Kesteven, 2000; SIGN, 2002; Aerospace Medical Association Medical Guidelines Taskforce, 2003; Possick and Barry, 2004; British Committee for Standards in Haematology, 2005; Watson, 2005; Geerts et al, 2008; Sándor, 2008; Schobersberger et al, 2008; Watson and Chee, 2008; Silverman and Gendreau, 2009; Smith et al, 2010].
Graduated compression stockings
- The recommendation to offer compression stockings is based on expert opinion as there is no good evidence on the use of compression stockings to reduce the risk of symptomatic travel-related deep vein thrombosis (DVT).
How should I advise someone at high risk of travel-related DVT?
For people assessed as having a relatively high risk of developing travel-related deep vein thrombosis (DVT):
- Assess the person's suitability for long distance travel. If appropriate:
- Consider seeking specialist advice, or
- Recommend delaying or cancelling the trip (for example people should postpone long-haul flights for 3 months after a hip or knee replacement).
- If travelling is unavoidable and involves continuous travel lasting more than 6 hours:
- Provide advice on general measures to reduce the risk of travel-related DVT.
- Advise the use of graduated compression stockings.
- Class 1 stockings or proprietary flight socks are generally sufficient.
- Measure the ankle-brachial pressure index (ABPI) if the person has symptoms of arterial disease. If the ABPI is less than 0.5, compression stockings should not be worn.
- For further information, see Compression stockings.
- Seek specialist advice from a haematologist regarding whether the use of low molecular weight heparin is indicated.
Additional information
- If low molecular weight heparin (LMWH) is prescribed:
- Ensure that appropriate arrangements are in place for LMWH administration (for example, that a nurse is available) or that the person is given training if the drug will be self-administered.
- If LMWH is indicated, it should be administered before departure.
- The British Medical Association warns that cabin crew are generally not trained in the administration of drugs by injection, and therefore the passenger or an accompanying person must be able to do this when necessary [BMA, 2004].
- Prescribe sufficient LMWH to cover the outgoing and any subsequent connecting or return flights.
- Prescribe LMWH as pre-filled syringes for ease of administration.
- Provide the person with a letter that explains why they have to carry needles and syringes while travelling, to show to security, immigration, and customs officials.
- Warn about the increased risk of bleeding and bruising.
- Advise the person to seek urgent medical advice if there is uncontrolled or excessive bleeding or bruising, or if they have a sudden severe headache (possible intracranial haemorrhage), or gastrointestinal pains (signifying possible gastrointestinal bleeding).
- Give advice on the safe storage and disposal of needles and syringes ('sharps').
Basis for recommendation
These recommendations are based on published guidelines, expert reviews and consensus documents [Kesteven, 2000; SIGN, 2002; Aerospace Medical Association Medical Guidelines Taskforce, 2003; Possick and Barry, 2004; British Committee for Standards in Haematology, 2005; Watson, 2005; Geerts et al, 2008; Sándor, 2008; Schobersberger et al, 2008; Watson and Chee, 2008; Silverman and Gendreau, 2009; Smith et al, 2010].
Use of graduated compression stockings and low molecular weight heparin (LMWH)
Seeking specialist advice
- Seeking specialist advice is recommended before prescribing LMWH because:
- The use of LMWH for the prevention of travel-related DVT is unlicensed.
- There is uncertainty regarding how LMWH should be used in the prevention of travel-related DVT [BMA, 2004].
- CKS found no clear guidance on the prescribing of LMWH (for example choice of preparation, dosage, time of administration, and duration of treatment) in high risk people, particularly if other risk factors are present (for example people with cancer).
How should I manage a person with a joint replacement or fracture?
- For people who have had a hip or knee replacement:
- Advise them to postpone long-haul flights for 3 months after surgery.
- For people with a fracture:
- Advise people with a plaster cast to have this changed to a split cast to reduce the risk of compression.
Basis for recommendation
How should I manage a person with a recent DVT planning long-haul travel?
- If the person has a newly diagnosed (within 2 weeks) deep vein thrombosis (DVT) or pulmonary embolism, seek specialist advice.
- If the person has been taking anticoagulants for 2 weeks or more:
- Reassure the person that they are at low-risk of developing a further thrombosis.
- Provide advice on general measures to reduce the risk of travel-related DVT.
- Consider prescribing graduated compression stockings. For further information, see Compression stockings.
Basis for recommendation
What general advice should I give to all long distance travellers?
- Offer reassurance that the risk of travel-related deep vein thrombosis (DVT) is very low in healthy people without risk factors (see Risks of developing travel-related DVT).
- Advise the person to avoid periods of prolonged immobility.
- Advise the person to maintain a normal fluid intake to avoid becoming dehydrated, and to avoid alcohol, which in excess leads to dehydration and inertia.
- Advise the use of graduated compression stockings for people assessed as having a relatively moderate or high risk of developing DVT.
- Aspirin is not recommended for the prevention of travel-related DVT (see Aspirin).
- People already taking aspirin (for example for cardiovascular disease) should not increase their dose.
- Advise the person to seek urgent medical advice (for example from a local doctor or the nearest Accident and Emergency department) if they develop the following after the trip:
- Swollen, painful legs, especially where one is more affected than the other, and/or
- Breathing difficulties (suggesting pulmonary embolism).
- Advise all travellers to obtain adequate medical insurance before they travel.
- They should declare all their medical problems (this will probably result in premium loading or cover excluding existing illnesses).
- For general health and travel advice (including insurance), see the Health advice for travellers booklet available from the Department of Health website (www.dh.gov.uk).
Advice to reduce immobility
- The following advice is issued by the Department of Health to reduce immobility during plane journeys [DH, 2007], and can be adapted for other long journeys, such as those by car or train:
- Sit comfortably in the seat and recline as much as possible.
- Wear loose-fitting clothing.
- Store hand luggage in the overhead lockers to keep the floor in front of the seat free from obstruction.
- While seated, bend and straighten legs, feet, and toes every 30 minutes 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 further improve circulation.
- 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.
- Avoid alcohol, which in excess leads to dehydration and inertia.
- Avoid taking sleeping pills, which also cause inertia.
Basis for recommendation
This advice is based on expert opinion and is in line with recommendations from the Department of Health, the World Health Organization, the British Medical Association, the British Committee for Standards in Haematology, and the Working Group of the British Cardiovascular Society [BMA, 2004; British Committee for Standards in Haematology, 2005; DH, 2007; WHO, 2008; Smith et al, 2010].
- Although there is no evidence to demonstrate that measures to increase mobility and minimize dehydration can reduce the risk of travel-related deep vein thrombosis (DVT), these recommendations are pragmatic, given that long periods of immobility and dehydration may predispose to DVT.
What advice should I give about graduated compression stockings?
- Graduated compression stockings are recommended for people assessed as having a moderate or high risk of travel-related deep vein thrombosis (DVT).
- Measure the ankle-brachial pressure index (ABPI) if the person has symptoms of arterial disease. If the ABPI is less than 0.5, compression stockings should not be worn.
- For further information see the section on Assessment in the CKS topic on Compression stockings.
- Advise the use of below-knee graduated stockings with an appropriate compression.
- Class 1 stockings (exerting a pressure of 14–17 mmHg at the ankle) are generally sufficient.
- However, for some people, a higher rating may be indicated to manage other conditions (such as oedema).
- For further information on the use of compression stockings, see the CKS topic on Compression stockings.
- Availability on prescription:
- Compression stockings are not available on prescription for the sole indication of preventing travel-related DVT.
- However, they can be prescribed for people with certain indications.
- For people who require a pair of class 1 graduated compression stockings (with a cost of two prescription charges) who are not exempt from prescription charges, advise that it might be cheaper to buy proprietary flight socks over-the-counter.
- Proprietary flight socks:
- These are widely available from pharmacies, airports, and many retail outlets.
- They provide a compression of 14–17 mmHg at the ankle (equivalent to class 1 stockings). However, flight socks with higher ratings (18–21 mmHg, similar to class 2 stockings) are also available.
- Stress the importance of ensuring that the socks are correctly fitted to provide adequate compression.
- This is particularly important in people with varicose veins, in whom there may be an increased risk of superficial thrombophlebitis.
- If in doubt, advise the person to seek advice from an appropriate healthcare professional (for example a pharmacist).
Additional information
- Graduated compression stockings (also known as elastic hosiery) may be prescribed for people with the following indications [Prescription Pricing Division, 2008]:
- Class 1 stockings (compression at the ankle 14–17 mmHg) for:
- Superficial or early varicose veins.
- Varicose veins during pregnancy.
- Class 2 stockings (compression at the ankle 18–24 mmHg) for:
- Varicose veins of medium severity.
- Treatment of, and prevention of the recurrence of, leg ulcers.
- Mild oedema.
- Varicose veins during pregnancy.
- Class 3 stockings (compression at the ankle 25–35 mmHg) for:
- Gross varicose veins.
- Post-thrombotic venous insufficiency.
- Gross oedema.
- Treatment of, and prevention of the recurrence of, leg ulcers.
Basis for recommendation
Basis for recommending compression stockings
- The recommendation to offer stockings for people at relatively moderate or high risk of developing travel-related deep vein thrombosis (DVT) is based on expert opinion.
- There is no good evidence on the use of compression stockings to prevent symptomatic travel-related DVT.
Rationale for using compression stockings
- Compression stockings are thought to reduce the risk of deep vein thrombosis by [Clarke et al, 2006]:
- Exerting graduated pressure on the leg, with the pressure being greatest at the ankle. When combined with muscular activity in the limb, this is thought to displace blood from the superficial venous system to the deep venous system.
- This, in turn, reduces blood stasis that can lead to clotting and increases the velocity and volume of blood flow in the deep venous system, thereby potentially preventing thrombosis.
Varicose veins and increased risk of superficial thrombophlebitis
- There have been case reports of people with varicose veins developing superficial thrombophlebitis whilst wearing compression stockings during long-haul flights [Scurr et al, 2001].
Should I recommend aspirin for the prevention of travel-related DVT?
- Aspirin is not recommended for the prevention of travel-related deep vein thrombosis.
- This includes the return flight for people who have undertaken high altitude activities.
- People already taking aspirin (for primary or secondary prevention of cardiovascular disease) should not increase their dose.
- If LMWH is prescribed, do not discontinue aspirin without specialist advice.
Basis for recommendation
Use of low-dose aspirin
- The use of low-dose aspirin for prevention of travel-related deep vein thrombosis is controversial and unlicensed [BMA, 2004].
- A single dose of aspirin (150 mg) before travel is recommended by the Scottish Intercollegiate Guidelines Network (SIGN), based on expert opinion [SIGN, 2002]. However, SIGN acknowledges that the balance of risk and benefit is difficult to estimate because the absolute risks of symptomatic venous thromboembolism with long distance travel, and the absolute risks of bleeding with single-dose aspirin, are undefined.
- CKS does not recommend the use of low-dose aspirin because there is no evidence to support this. This is in line with current guidance issued by the Department of Health, World Health Organization, British Medical Association, British Committee for Standards in Haematology, and the American College of Chest Physicians [BMA, 2004; British Committee for Standards in Haematology, 2005; DH, 2007; Geerts et al, 2008; WHO, 2008].
For people already prescribed aspirin for cardiovascular protection
- The Department of Health does not recommend increasing the current dose of aspirin [DH, 2007].
- CKS found no guidance on managing low-dose aspirin therapy for these people if low molecular weight heparin (LMWH) is indicated. Feedback from CKS expert reviewers generally indicated that aspirin for cardiovascular protection should be continued, taking into account the increased risk of bleeding. Consequently, CKS advises seeking specialist advice when LMWH is indicated for people prescribed aspirin for cardiovascular protection.
For people undertaking high altitude activities
- Because of the lack of evidence and guidance, CKS does not recommend the use of aspirin before the return flight for people who have undertaken high altitude activities. This is supported by feedback from CKS expert reviewers.