Long journeys and leg clots
Sitting for several hours on a plane, bus or in a car is one of the temporary risk factors for a vein clot. This article describes who is more at risk, what simple steps help on a journey, where compression stockings stand in the evidence and which signs to take seriously.
People sometimes come back from a journey with swollen ankles. Most of the time the swelling is harmless. But in a few cases, one leg becomes heavy, painful and swollen after a long journey. This article is about that case.
Why does travel raise the risk?
The UK’s National Health Service (NHS) counts a journey of more than four hours by plane, car or train among the temporary risk factors for a deep vein thrombosis, alongside a hospital stay, surgery, three or more days of complete rest, pregnancy, the six weeks after giving birth and dehydration.
There are lasting factors too: age over 60, being overweight or obese, smoking, a previous clot, varicose veins, cancer, heart failure, and pills and hormones that contain oestrogen (NHS). The more factors that come together, the more seriously a long journey should be planned. Which group you are in and what precautions you need is decided by a doctor.
What can we do on a journey?
For a journey of more than four hours the NHS says:
- Wear loose clothes.
- Drink enough fluids and do not drink alcohol.
- Move whenever you can and do not sit still for long. Get up and walk about every hour.
These cost nothing and suit everyone.
Compression stockings on a flight
A Cochrane review (2021) examined twelve trials with 2918 travellers on flights of at least four hours. The results:
- In the trials that compared stockings on both legs with no stockings, fifty of the 2637 people with follow-up data had a symptomless clot: three in the stockings group and 47 in the no-stockings group. The authors call this high-certainty evidence.
- Leg swelling was lower in the stockings group (low-certainty evidence).
- Superficial clots were also fewer in the stockings group, but the difference was not statistically certain.
- No serious side effect was reported.
- Deaths, lung clots and symptomatic clots were not seen in these trials, so nothing can be said about the effect of stockings on them. The authors say a much larger trial would be needed for these outcomes.
So stockings reduce the symptomless clots found by ultrasound, but we do not know how much effect they have on the real, symptomatic risk. Do not choose stockings on your own in every situation. Arterial disease of the leg or another condition may rule them out (NHS, on stockings for varicose veins). Ask a doctor.
If you take a blood thinner
The NHS says that after a deep clot, flights and long journeys should be put off until at least two weeks after starting the medicine. Do not stop the medicine on your own and discuss the plan with your doctor before you travel, because your situation differs from others’.
After the journey: the signs
The NHS lists these as signs of a deep vein thrombosis:
- Throbbing pain in the calf or thigh, usually in one leg
- Swelling of one leg
- Redness or darkening of the skin
- Prominent veins
If you see any of these after a journey, go to a doctor or a healthcare facility the same day. A suspected clot should not be put down to the tiredness of travel.
If leg swelling and pain come with shortness of breath, chest pain, coughing up blood or fainting, the clot may have reached the lung. Call 115 (the emergency number in Iran). If you are outside Iran, call your local emergency number. The NHS stresses that you should not drive yourself and should take your medicines with you.
Summary
A long journey is only one of the temporary risk factors for a clot. Moving, drinking fluids and wearing loose clothes can always be done. If you have several risk factors, talk to a doctor before travelling. And if one of your legs swells and hurts after a journey, have it checked the same day.