The prolonged immobility of flight passengers during long-haul air travel increases the risk of developing blood clots, which could prove fatal especially to people whose travel occurs just prior to major surgery.

The formation of a blood clot within one of the large, deep veins of the pelvis or lower limbs, often in the deep veins of the calf, thigh, knee or pelvis, is referred to as deep vein thrombosis ( DVT ).
A pulmonary embolism can form when the blood clot breaks into smaller pieces, floats in the blood and becomes lodged in the blood vessels supplying the lungs, which may result in sudden death.

Juraj Sprung and colleagues analyzed patient information at Mayo Clinic and found that of 181,765 patients who underwent operations between 1998 and 2002, a total of 3,736 lived outside of the United States, Canada and Mexico and traveled on average more than 5,000 miles prior to surgery.

These long-haul travelers experienced over 30-times-higher incidence of dangerous blood clots or pulmonary embolisms within 28 days of surgery compared to the surgical patients who either did not travel or traveled within North America. The facts that an average age of these patients was much lower, and that blood clots occurred much earlier after surgery suggest that long distance travel before surgery represents an increased risk for dangerous clots ( DVT ) and its severe complications such as pulmonary embolism.

Sprung notes increased awareness among airlines and other agencies about the risks of blood clots forming during long-haul air travel, but additional measures may be needed for those who travel to have the surgery. He says several factors contribute to the risk of blood clots forming in the veins, including long periods of immobility during flight, restriction of leg veins due to compression on the legs from the edge of the seat, and possibly dehydration due to decreased fluid intake or excessive use of alcohol during the flight.

The authors recommend that patients traveling long distances prior to major surgery be told of the potential for increased risk of complications with blood clots. During the flight, patients can take preventive measures by staying well hydrated, exercising and wearing elastic compression stockings. High-risk patients also can benefit from prescribed medications to prevent the problems.

In a second study, researchers noted a marked association between the duration of anesthesia for patients undergoing hip or knee replacement surgery and blood clots in the veins after surgery.

Analysis of the patient data suggests a threshold of anesthesia duration that increased the odds of a patient having blood clots in the veins. The information indicates that 3.5 hours ( 210 minutes ) is the threshold. The longer duration of anesthesia is usually related to how long it takes the orthopedic surgeon to perform a major joint replacement. It makes sense that this raises the risk of blood clots in the veins because the patient is supine and blood pools in the areas.

Daniel Brotman, director of the hospitalist program at Johns Hopkins Hospital, and his colleagues recommend further study to examine the risk and prevention of postoperative blood clots in the veins and the relation to anesthesia duration. Approximately 500,000 patients undergo total joint arthroplasty, either hip or knee, in the United States each year. Patients are treated with drugs to combat the blood clots in the veins during surgery, but up to 38 percent may still develop the condition. And although they are small clots, approximately 5 percent result in a fatal pulmonary embolism.

Source: Mayo Clinic Proceedings, 2005


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