January 10, 2012 in Features

To prevent DVT, keep legs moving

Anthony L. Komaroff, M.D. M.D.

DEAR DOCTOR K: My 61-year-old mother plans to take a long plane trip. Her legs usually become swollen when she flies a long distance. Should she take any precautions so she doesn’t develop a blood clot in her legs?

DEAR READER: Long flights increase anyone’s risk of developing mild swelling in the feet, ankles and lower legs – and of getting blood clots in the legs. Swelling is common; blood clots are uncommon.

On a long flight, unless you’re in a fully reclining first-class or business-class seat, you are not lying flat. Gravity is pulling blood down into the veins of your lower legs. Also, your legs are bent at the knees. This makes it harder for blood to travel through your leg veins and back to your heart. As a result, the veins swell up.

On a long flight, you also don’t walk a lot. When you walk, your leg muscles squeeze your veins, which keeps the blood flowing back to your heart. But if you are inactive for many hours, this also causes the leg veins to swell up.

When your leg veins swell, some of the fluid in the blood leaks out into the tissues of your legs, causing the swelling. Also, the flow of blood in your leg veins slows down. When blood flow slows, clots tend to form.

Blood clots that form in the veins of the legs are called deep-vein thrombosis (DVT). A DVT blocks blood flow and causes pressure to build up in the vein. This can cause long-lasting problems in the affected leg.

What can your mother do to protect herself against both leg swelling and DVT?

There are three ways to prevent DVT (be sure to pass them along to your mother): First, stay well hydrated. Drink enough nonalcoholic beverages to force you to get up to make frequent trips to the toilet.

Second, do in-seat exercises to keep the blood flowing through your legs. For example, contract and relax your calf muscles, or rapidly wiggle your feet up and down.

Finally, get up to walk every hour.

Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions: www.AskDoctorK.com.

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