You may find it easier to walk with your new hip or knee replacement, but watch out the next time you have to sit still for several hours on an airplane. • According to research just published in the Annals of Internal Medicine, you might want to take a blood thinner, or at least a baby aspirin, before getting on an airplane so blood clots won't form in your legs as you sit for hours in a cramped seat, barely able to move. • The risk of blood clots in the legs, known as deep-vein thrombosis, or DVT, goes up for everyone on airplanes. The condition often goes unnoticed, but severe cases can cause painful swelling and inflammation, often behind the knee. If a large clot breaks loose, it could travel to the lungs and cause a pulmonary embolism — a medical emergency that can lead to death.
The best way to lower risk remains the simplest: Get up and walk at least every couple of hours while you're in the air. This advice becomes even more important as people get older, since the risk of DVT goes up with age.
People who get a knee or hip replacement, however, become even more prone to DVT, according to the new research, but a blood thinner reduces risk.
One study led by Diana M. Sobieraj, a professor of pharmacy at the University of Connecticut School of Pharmacy, found that prolonged treatment with blood thinners reduced the risk of blood clots and pulmonary embolism in people who had major orthopedic surgery, such as a joint replacement or hip surgery.
Another study in the same issue found that a class of anticoagulant drugs known as oral direct factor Xa inhibitors provided slightly better protection against DVT.
"Our review showed that the difference in terms of efficacy between the classic drugs for preventing thrombosis after hip or knee replacement and these new drugs is quite small," said Dr. Ignacio Neumann of McMaster University in Canada. "But the big advantage is the direct factor Xa inhibitors are pills, while the low molecular weight heparins are injections."
He also said that better surgical techniques and postsurgical physical therapy, along with new anticoagulants, have reduced the risk of DVT in people who have had a joint replacement. Among people who receive a joint replacement and receive blood thinners, "probably only 1 patient in 100 will have a thrombosis in the 3 months after surgery," Neumann said.
But DVT isn't the only threat you face when you get on an airplane.
Although airplanes are pressurized, cabin pressure tends to drop at high altitudes, which means you'll inhale less oxygen with each breath — a potential problem for passengers with cardiovascular disease, according to Australian physicians James A. Low and Daniel K.Y. Chan, who have written a paper on the strains that air travel places on the aging body. Prolonged low oxygen conditions also could produce changes in thinking, they add, and cause fainting, which is one of the most common in-flight medical emergencies, especially among the elderly.
Low cabin pressure also may allow expansion of gases in body cavities such as the sinuses, the middle ear, intestines and even the teeth. This can cause pain.
Low humidity can dry out the eyes and the nasal membranes and cause dehydration. Drinking water helps, according to Low and Chan, but you might want to avoid alcohol and diuretics to reduce trips to the bathroom.
Also, prolonged sitting, besides increasing the risk of DVT, can aggravate arthritis and cause swelling in the lower leg.
"More older people are traveling by air, and most will complete their journeys uneventfully," Low and Chan write. "Certain actions may help to minimize problems."
Tom Valeo writes frequently about health matters. He can be reached at firstname.lastname@example.org.