NEW YORK (Reuters Health) - Drinking a beverage containing electrolytes and carbohydrates during long airplane flights may be superior to water in preventing the development of potentially dangerous blood clots, Japanese researchers report.

"Consuming (electrolyte and carbohydrate beverage) during flight resulted in lower urine volume and increased fluid retention, when compared to water," lead author Dr. Hirofumi Okoshi, a physician at Japan Airline's Medical Services in Tokyo, Japan, told Reuters Health.

Dehydration is a concern on long airplane flights because it may increase the risk of deep vein thrombosis (DVT), in which blood clots form in the legs. DVT in turn increases the risk of pulmonary embolism, a potentially deadly condition that occurs when a blood clot lodges in the lungs.

The researchers conducted a test of 40 healthy men on a 9-hour overseas flight. The passengers were randomly assigned to drink either the fortified beverage or plain water immediately before takeoff and four times during the flight. In total, the study participants consumed about 1.3 liters of their assigned beverage.

Urine samples were collected every two hours during the flight and blood samples were drawn upon landing. The passengers' body weights were measured before boarding and again after landing.The drink, called Pocari, contains sodium, potassium and carbohydrate, and is manufactured by Otsuka Pharmaceutical Company in Tokyo, Japan, the funders of the study. The findings were published in a research letter in the February 20th issue of the Journal of the American Medical Association.

The researchers reported that those who drank the fortified drink had a significantly greater net fluid balance at the end of the flight. In addition, those who had the electrolyte- and carbohydrate-containing drink were less likely to have an increase in the thickness of the blood in their legs, which may contribute to blood clots.

"Supplying fluid in this situation is to prevent hypovolemia (reduced plasma volume), a factor of blood clotting, and to prevent concomitant elevation of blood viscosity," Okoshi explained.

The researchers conclude that the beverage may be a better method of maintaining hydration than plain water during long airplane flights.

Even if patients can't stay awake in order to consume the beverage every two hours, he noted, a smaller amount may still have some beneficial effect.

However, Okoshi pointed out that an increase in blood viscosity and a reduction in plasma volume are only one of many clotting factors involved in DVT, and preventing them will not guarantee that clots don't form in the legs.

In all situations requiring people to sit for long periods of time, he noted, "it is important for the passengers to be aware of the risk factors, to periodically drink adequate amounts of fluid and to exercise (their) lower extremities as a preventive strategy."

"I certainly believe dehydration as a cause of the thickening of the blood is one of the contributing factors (to DVT)," noted Dr. Bo Eklof, clinical professor of surgery at the University of Hawaii, who recently attended a World Health Organization conference in Geneva on the issue. "Theoretically, to add electrolytes to the fluid is a positive idea. I think we need more research, but the principal is correct."

SOURCE: Journal of the American Medical Association 2002;287:844-845.

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