DVT

Deep Vein Thrombosis in Travellers
Key Points
A deep vein thrombosis (DVT) is a blood clot in the veins of the leg. Pieces of this clot can break off and lodge in the lung: pulmonary embolus. Large emboli can cause severe illness or sudden death.

Is flying associated with deep vein thrombosis?	Yes, but only as much as any other activity where we are relatively immobile (sitting in the theatre or on a train)

Is the risk lower in business class?	There is no evidence for this. The term "Economy class syndrome" is a marketing myth of the media

What is the risk?	No studies have yet defined the level of risk. Death from a pulmonary embolus after a flight, however is rare

Who is most at risk?	The elderly, those with illnesses such as diabetes or arthritis or who have had surgery recently, smokers, those with a family history of blood clotting disorders, pregnant ladies

How can risks be reduced?	Sitting, get an isle seat, walk regularly up and down the cabin, avoid / minimise alcohol. Aspirin may give some protection but also has potential ill effects : best taken only by those who need to take it for other medical reasons. Compression stockings giving graduated compression from the feet up to at least the knee are effective but are hot and uncomfortable. Anticoagulants (e.g. Heparin) are effective but are inconvenient and can cause bleeding. See your doctor for advice if you believe you have two or more of the risk factors above

How do I know if I have a DVT?	The textbooks describe a swollen painful red calf which is tender to touch and painful to stand on. Up to 30% of people with DVT, however, have no signs of anything wrong at all. The vast majority of DVTs get better by themselves - often without the individual knowing anything about it.

What is a pulmonary embolus?	If a piece of blood clot - from a DVT - breaks off it will pass round the circulation and lodge in the lungs. Small emboli may pass unnoticed; larger ones will give chest pain, sudden shortness of breath and bleeding into the lungs - blood is often coughed up. Very large emboli will prevent effective blood flow through the lungs all together, leading to death.

What can I do if I think I may have a DVT or a pulmonary embolus ?	Call a doctor immediately. There is no first aid for a DVT. If you have symptoms which fit the picture for a pulmonary embolus you must see a doctor immediately

What is Deep Vein Thrombosis?
A deep vein thrombosis or DVT is a blood clot which forms in the deep veins of the legs. Apart from discomfort and swelling in the affected limb, pieces of thrombus (clot) can break off, pass through the heart and lodge in the lung. Small clots in the lung (pulmonary emboli) cause no or minimal lasting effect; large clots cause chest pain, bleeding into the lung and may lead to death. Unfortunately most people with DVTs have no symptoms, and most pulmonary emboli occur without obvious signs of a DVT. It is therefore important to : • Identify risk factors for DVT • Make information available on prevention • Increase awareness of the symptoms of DVT and Pulmonary Embolus • Provide diagnostic services and treatment early
Risk factors for DVT in travellers:
Travel : There are good theoretical reasons to believe that air travel should carry a higher risk than other forms of travel. In spite of recent publicity and law suits there is no evidence that this is so. Immobility and the length of the journey are the principal factors in DVTs for the traveller. Other factors - dehydration, jet lag and reduced oxygen tension make surprisingly little difference. A literature search carried out by MSO found two papers describing the "economy class syndrome". In spite of the titles of these papers, however, there appears to be no evidence that Economy Class travel is any more of a risk factor for DVT than Business or First Class travel. Recent surgery : Any surgery will increase the risk of DVT. Surgery to the hip, thigh, or abdomen carries the highest risk. If an employee must travel within two months of such surgery professional advice must be sought. Previous DVT : Those who have had a DVT in the past are at high risk of a DVT in the future and should receive professional advice before contemplating a long flight. • Age: those over 40 yrs of age are at greater risk. • Pregnancy : graduated compression stockings should be worn • Contraceptive pill (with oestrogen) - minimal increased risk • Steroid medication : graduated compression stockings should be worn • Overweight • Varicose veins : graduated compression stockings should be worn • Blood clotting disorders : should be screened for in those with recurrent DVTs • or a history of >1 DVT in a first degree relative (parents, siblings and children) • Smoking : probably a risk factor for DVT
Preventing DVT
Exercise in flight : No papers have been published demonstrating benefit from leg exercises in flight, but there are empirical reasons to believe it to be effective. The following are recommended : • Sufficient room to stretch the legs out • Aisle seat • Regular walks in the cabin (e.g. hourly) Easier than these will be the simple exercise of alternately pressing one foot down onto the top of the other - perhaps 50 times per hour. Anticoagulants : Heparin and Warfarin are highly effective in preventing DVTs. Heparin, however must be given by injection, and Warfarin is effective only after several days of treatment. Both require regular blood tests to ensure effectiveness and to prevent bleeding from excessive doses. In spite of these drawbacks low-dose Heparin may be recommended for frequent travellers with a history of DVT in the past and continuing risk factors. The advice of a travel physician will be needed with information from a thorough health assessment. Compression stockings or tights are effective, cheap and easy to use. Design and fitting are important to ensure that the pressure applied is graduated - more at the foot and ankle and progressively less further up the limb. They are not a popular choice with travellers, however as they feel hot and tight, and tend to fall down. In spite of these drawbacks they are the most practical and effective of the options available for most travellers at significant risk. Adverse effects of their use should be nil - if they are worn correctly. The temptation to fold the top of the stocking over to keep it up, however is too much for many people : the relative obstruction that this causes can trap blood in the leg - so actually increasing the risk of DVT. Aspirin : There is some evidence that Aspirin is effective in reducing the risk of DVT but not sufficient for a recommendation to be made for its use solely for this reason. The dose which will give the greatest potential benefit with the least risk of side effects remains unknown. Low dose Aspirin (75mg daily) is recommended in the UK for all those with more than a 15% ten year risk of stroke or heart attack - assuming no contraindications. If all travellers with such risks took Aspirin - and few do - there might well be a beneficial effect on the rate of DVT and Pulmonary Embolus.[A 15% ten year risk equates to all persons over 50 with one or two cardiovascular risk factor, and some younger persons with multiple risk factors. Risks include smoking, high blood pressure, diabetes, significant overweight, and high cholesterol. Formal screening for these risks in travellers is certainly worthwhile.
Symptoms & Signs of DVT and Pulmonary Embolus
Most DVTs, unfortunately are without symptoms or signs. Any pain, redness or swelling in the calf, however should alert travellers to the possibility of a DVT, and medical help should be sought at once. The further the blood clot extends up the leg the more risk there is of a part of it breaking off and causing a pulmonary embolus. Signs in the thigh are therefore always of medical significance. Like DVTs, pulmonary emboli can also occur without any symptoms. Signs to look out for, however include chest pain, shortness of breath, and a cough producing blood. Any one of these signs should be investigated immediately, and advice should be sought from a western doctor if services are of a questionable standard overseas.
Conclusions
• The incidence of DVT and Pulmonary Embolus in travellers is unknown. • DVTs are probably common, and pulmonary emboli often fatal. • Travel of any sort over 4 hours is associated with DVT. • Important issues in prevention are general fitness, exercises during flight, and perhaps Aspirin • (in those for whom there is another medical indication). Those with significant risk factors should receive specialist advice ideally from a travel physician - otherwise from their family doctor. Significant risks include previous DVT, pregnancy, and recent surgery.