Blood Clots - What You Need to Know

General Medical

Dr. Nikki Stamp

Every now and again, we see a story of how someone was on a long-haul flight. After they landed, they became unwell and it was because they had a clot in the legs or a clot in their lungs and we call this the economy class syndrome. The stories are quite scary but as always there’s a fair bit of misinformation around so let’s clear some of that up.

When we talk about economy class syndrome, we’re usually referring to two related conditions. The first is called deep vein thrombosis or DVT where a clot forms in the veins of the legs and pelvis usually in response to being immobile or some other causes. The clot here can cause pain and swelling in the legs. If this clot breaks off and makes it way up to the lungs, we call this a pulmonary embolus and this is the most feared complication of a DVT.

Blood clotting is actually a good thing. We evolved to be able to clot in response to injury so that we don’t bleed to death. However, sometimes clots form when they aren’t needed. There are three things that happen to cause blood to clot. The first is stasis, or blood not flowing normally, the second is a kind of thickening of the blood and concentrating all the little factors in our blood that cause it to clot. The last thing is damage to the lining of our blood vessels which is natures little trick in case we’re hurt – it’s a powerful blood clotting safeguard.

In DVT, these processes happen due to a number of factors. The risks for getting a DVT include immobility, cancer, smoking, recent major surgery, obesity, smoking and some medicines. Some forms of the oral contraceptive pill can thicken the blood making clots more common. Some people have inherited a tendency to clot more easily and they can develop a DVT without any of these problems. All of these things cause thickening of the blood, or lower flow and vessel injury and clots to form.

Most clots that travel to the lungs tend to come from the bigger veins in the upper legs and pelvis. Over half of people with a PE also have clots in the legs. When a pulmonary embolus, or PE, occurs, the blood supply to a section of the lung gets blocked off. This can make someone very sick with shortness of breath, pain in the chest and in some cases, heart failure which can result in the heart stopping (or cardiac arrest) if the clot is particularly big.

The risk of getting a blood clot is really determined by how many risk factors someone has; the more they have, the more likely they are to get a clot. Incidentally, long-haul flights carry around a 0.5-1.5% risk of developing a clot in the legs. Most of us don’t need special treatment of blood thinners before a long flight, bus ride or train ride, but if you’re unsure, check with your doctor.

Preventing blood clots for most people is really centered around movement. It’s why on a plane, particularly on a long flight, you’re encouraged to move. This keeps the blood moving so that it doesn’t pool and clot. For some people who have a lot of risks, they may take blood thinners either by an injection or a tablet and we routinely do this for people in hospital or who are undergoing surgery because they have a very high risk.

If someone does get a blood clot, we use medicines either injected or tablets, to thin blood and allow the clot to dissolve. Uncommonly, for PE, heart surgery is needed but this doesn’t happen very often.

Prevention is the best thing when it comes to DVT and PE so remember to keep moving and if you’re in hospital, don’t be afraid to ask your doctors and nurses if they’ve got you on treatment to prevent clots.


Please note: Dr. Nikki's blog is general advice only. For further information on this topic please consult your healthcare professional.

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