Preventing A Hidden Danger of Travel

By: David A Fein, MD

The death of a close friend is often the reason for someone to finally decide to check on their own health. So I was not surprised when a worried but otherwise healthy new patient told me that the sudden and unexpected death of his long-time friend from an apparent heart attack had motivated him to make his appointment.

His friend was in his 40’s and had been in seemingly great health. He ate well, exercised daily and had no signs of ill health. But while out for his daily run, he stopped for a moment to read a map and then collapsed without warning. It turned out that his friend was running in the streets of Rome after having flown there just the day before he died. While there is no way to prove the diagnosis now, it is very possible that his death was not due at all to coronary artery disease. Instead, he may have succumbed to a common and preventable complication of extended travel, deep vein thrombosis.

A Deep Vein Thrombosis (DVT) is a blood clot that forms in the veins of the legs. The legs have two sets of interconnected veins. The superficial veins are just below the skin. The deep veins are embedded within the muscles of the calf and thigh. A blood clot, or thrombosis, can form in either set of veins but clots in the superficial veins are generally not considered dangerous. Superficial thrombosis may cause localized pain and swelling that will generally resolve with elevating the leg, applying heat and taking ibuprofen.

Thrombosis in the deep veins can be much more serious. Although most DVT’s will safely resolve with appropriate treatment, clots in the deep veins pose a risk that all or part of the clot can break free and travel up the vein. The clot can quickly make its way through the right side of the heart where is will become lodged in the arteries to the lungs. When this occurs it is known as a Pulmonary Embolus (PE). The clot impairs the blood flow to one or more segments of the lung. Depending on the size and location of the PE, this may range from causing little or no symptoms to causing chest pain and breathing difficulties. In some cases, this can cause the victim to cough up blood or can mimic an asthma attack, including wheezing. More severe PE’s can cause enough obstruction of blood flow through the lungs that the blood pressure drops to dangerous levels or even cuts off blood flow entirely. A very large clot can suddenly block off all blood flow from the heart to the lungs and cause the kind of sudden death my patient’s friend might have experienced.

Prolonged travel, such as sitting for hours in a car, train or airplane, increases the risk of DVT. While the overall risk is very small ( some studies place the risk at about 1 DVT for every 6000 hours of travel lasting 4 hours or more) with more than 40,000 airline flights each carrying hundreds of people every day that risk translates into hundreds of DVT’s every week related to plane travel.

The primary cause of DVT’s during travel is immobility. Sitting for prolonged periods causes blood to pool in the veins of the legs. Blood that is not rapidly flowing may be more likely to clot. Some medical conditions such as heart failure, obesity, prior history of DVT, clotting disorders, some cancers, contraceptive pills or hormone replacement therapy may increase the risk of a DVT. The decrease in cabin pressure in airplanes and the dehydration that results from low humidity and prolonged periods without access to fluids might also play some role in making DVT a bit more likely with air travel compared to other forms of travel. Certainly, it is more difficult to move around during a long flight than on a train or in a car.

There are some simple steps that can help to prevent clot formation in the legs when you are traveling:

  • Drink lots of liquids before and during travel. Dehydration makes clot formation more likely. Limit your alcohol intake as alcohol worsens dehydration.
  • Wear loose clothing. Tight socks, stocking, pants, etc., can act like a tourniquet and cause more blood to pool in the legs or slow the blood flow.
  • Move frequently. You should try to get up and take a short walk every 30-45 minutes. If this is not practical, curling your toes and contracting your calf muscles for 2-3 minutes every half hour will also help to move blood back up out of the legs. Taking sleeping pills on long flights may increase your risk of DVT because you are immobile in a seated position for hours without any exercise.
  • Take an Aspirin. Aspirin acts as a blood thinner and can prevent clot formation. However, the evidence is stronger that aspirin prevents clots in arteries than in veins (arterial clots are not a travel-related concern for most people) We generally recommend an aspirin prior to travel for those who will be in cramped seating for more than about 5 hours. (Remember, even a short flight can become a long one these days with airport delays) Although it may not be helpful, the risk of a single aspirin tablet is extremely small.
  • Those at highest risk should consult with their physician prior to prolonged travel. Special compression stockings are available that may help to further reduce the risk of DVT for those patients. In those at particularly high risk, anti-coagulation therapy may be warranted.

Once you arrive at your destination take a short walk to get the blood moving in your legs again. While the vast majority of travelers will never experience a DVT, if you experience a swollen or painful calf (more than the mild swelling of both ankles and feet that commonly occurs with air travel), difficulty breathing or chest pain in the days following your trip consult a physician immediately. DVT is generally easy to detect and once it is found effective therapy is available that can reduce the risk of Pulmonary Embolus and help to minimize the long-term after effects in the legs.