Concerns about DVT (deep vein thrombosis) in travellers have led to much discussion in the media and medical circles about measures that might be taken to reduce the risk.
How risky is it?
One study identified a risk of around 4.8% on long haul flights, but other long distance travel is also associated with a lesser risk. Certain groups of people are at greater risk of DVT, including those aged above 40, women who have recently had a baby, women taking the contraceptive pill or HRT, people with a previous history of blood clots, and people with certain blood and circulatory disorders. Major surgery in the previous 3 months, especially hip or knee surgery, also increases the risk. High risk people make up 90-95% of those who get DVT. Around 1% of people with a DVT will die as a result of a pulmonary embolism. This is where a piece of the blood clot in the leg travels to the lungs, where it can lead to collapse of the lungs and heart failure.
How can the risk be reduced?
For low risk travellers, some simple measures can help. It is generally recognised that the risk relates to passengers remaining immobile in the seated position for long periods of time, and sluggishness of the circulation. At altitude, the blood becomes thicker and more likely to clot.
Drink plenty of water. As a rule of thumb, I advise my patients that they should be drinking enough to need to go to the toilet at least every 2 hours. The trip to the toilet has additional value as it stretches the legs and stimulates the circulation. Try to resist the on-board alcohol. Keep the intake low as it leads to dehydration and sleepiness. Move around the plane as much as possible. This isn't always easy if you're in a window seat and don't want to disturb fellow travellers, but do your best. Whilst sitting, do leg exercises for 5 minutes, every half an hour. Rotate the ankle joints slowly in both directions, and transfer weight from your heels to the balls of your feet repeatedly. Avoid pressing the backs of your calves against the front of your seat. Use the footrest under the seat in front of you.
What about aspirin and flight stockings?
Flight stockings should certainly be worn by high-risk travellers, and may also reduce the risk for others. They are widely available from pharmacies.
The role of aspirin in preventing travel-related DVTs is controversial. There is at present, insufficient evidence to recommend aspirin for low-risk travellers. Aspirin may be useful for high-risk travellers, but more work needs to be done to establish the best dose, and a dosing plan in relation to travelling arrangements. Certainly, aspirin would need to be started before the flight and continued for a period of time after travelling. Because evidence is scanty, and because aspirin can cause serious side-effects such as bleeding from the gut, bruising, and allergic reactions, the present advice from the Department of Health states that there is no convincing evidence to date that aspirin can prevent DVT in air travellers.
