DVT – The Persistent Challenge

September 05, 2013

In 2001, the respected medical journal The Lancet published a bombshell analysis estimating that small blood clots form in the calves of in one in every ten airline passengers. The controversial study sparked heated debate.

Now, 13 years later, some important perspective on air travel-related blood clots, a clearing of the air if you will. Further research indicates they’re not so much a plague as a problem. Things may not be as bad as we once assumed, but the fact is Deep Vein Thrombosis remains a devilishly persistent issue that may be on the grow. One of the world’s foremost DVT experts, Dr. Nigel S. Key, chair-elect of the International Society of Thrombosis Haemostasis (ISTH), asserts, “It would be a reasonable supposition that as long-distance airline travel becomes more affordable – and as the population gets older – that DVT is becoming more widespread.”

Another renowned researcher, Dr. Suzanne C. Cannegieter of the Department of Epidemiology at Leiden University Medical Center in the Netherlands, roughly estimates that world wide there were some 250,000 cases of air travel-related DVT in 2012. As approximately 5 per cent of DVT cases are fatal, this would put the death rate at 12,500 last year.

That risk comes against the backdrop of a significant increase in people who fly these days. The International Civil Aviation Organization (ICAO) says some 1.639-billion of us took wing back in 2002. According to estimates by the International Air Transport Association that number ten years later (2012) is 2.977 billion.

The US Centers for Disease Control and Prevention, says, “The actual incidence of travel-related [venous thromboembolism, which includes DVT and PE] is difficult to determine.” Still, CDC concludes, “Long distance air travel may increase the risk…by 2- to 4-fold,” noting that heightened risk is also present in car, bus or train travel – any mode of transportation where passengers are relatively immobile.

Anatomy and Consequences of Clots

Key says most clots from in the lower extremities, the legs and the pelvis. Sometimes they manifest themselves dramatically: “There are well-publicized cases of somebody getting off an Australia to [London] Heathrow flight and dropping down dead of a pulmonary embolism.” Then there are instances “where patients present several weeks later, ” he says. In the middle are flyers such as our Hong Kong to Chicago traveler, where preliminary symptoms – such as leg cramps – are followed in short order by something more attention grabbing. “I woke up and my leg was swollen and I couldn’t move,” she vividly recalls.

It’s when an extremity-lodged clot breaks off and travels to the lungs that all hell can break loose. “The majority [of patients] will present with Deep Vein Thrombosis rather than Pulmonary Embolism,” says Key. “That’s about a two-to-one ratio.” You may have time to stop potentially-fatal PE consequences from happening because “It could take a while for [the clot] to grow, propagate [from, say, the leg] and eventually obstruct – or embolize and travel to the lung.”

What You Can Do to Minimize the Risk

“Clots don’t form for one reason” alone he says. Many times, they’re the result of a perfect storm of factors, a malicious mélange of little things: age, immobility, recent surgery or hospitalization, long-distance flights or dehydration.

First, consider that statement of Key’s that more older folks are flying these days. They should take special care. For the overall population, Key says the risk of DVT is about one in a thousand. For people under 40 it’s one in ten-thousand. Then there are octogenarians. Live north of 80 and the chances of DVT increase ten-fold – one percent of that population.

This doesn’t mean older people shouldn’t fly; it just means they (and the rest of us for that matter) have to be acutely aware of DVT and how to keep it at bay: hydrate, avoid excessive alcohol and caffeine, choose an aisle seat (preferably in proximity to a lavatory), don compression hose or socks, get up and walk about when the seat belt sign’s not on. “All of that,” says Key. Then there’s awareness of the increased risk oral contraceptives pose, as well as recent surgeries. As for the latter, the good doctor says, “Better wait a good month or six weeks [after surgery] before undertaking a long trip.”

How about passengers with a history of DVT? Should they travel? Key has a patient who regularly flies to Nigeria for his work. He’s been hit by clots before. Key says, “There are some patients where we might give them a one-time, preventative dose of anti-coagulant just before they get on the plane.” That’s supplemented  by another dose within 24 hours after the flight, followed by a similar regimen on the return leg of the journey.

This internationally-recognized thrombosis expert is not suggesting this prophylactic prescription en masse. He’s merely saying the benefit-to-risk approach might work “on an individualized basis.”

As for taking an aspirin before you board, Key says, “it’s not known” whether that makes a difference. But for patients whose risk is “several deviations from the normal…we will say, ‘Why don’t you take this dose before you get on the plane, and maybe one after you arrive.’”

That’s the point of all of this: arriving at your destination in decent shape to wrestle the business at hand, or simply revel in those far-away-places with the strange sounding names. Neither is  accomplished from a hospital bed.