When runners collapse or get sick at the end of a long race, it
seems logical to give them fluids. Sometimes, however, water is
the last thing these athletes need. All had taken in too much water
during their races, causing sodium levels in the blood to drop.
From there excess water is absorbed into blood and fluid builds
up in the brain. Eventually, fluid accumulates in the lungs, and
athletes become breathless and nauseated.
When runners collapse or become ill, the natural assumption may
be that they are having a heart attack. Yet, rather than being a
sign of heart attack, fluid build-up in the lungs -- called pulmonary
edema -- may signal brain swelling.
The investigators describe the cases of seven marathoners who collapsed
and had nausea and vomiting after their races. When brain scans
revealed swelling, six of the patients were treated with an intravenous
solution containing high amounts of sodium -- a water-depleting
treatment that is directly the opposite of the low-sodium solutions
that runners may receive if they are misdiagnosed. The seventh patient,
who was not diagnosed with brain swelling, later died; an autopsy
revealed that there had indeed been fluid on the brain.
Five of the patients were female, suggesting that women may be
more prone to water intoxication and its effects on the brain and
lungs. All seven had a history of using nonsteroidal anti-inflammatory
drugs -- painkillers that include aspirin. These drugs can block
the excretion of water from the body. Runners who become breathless
and nauseated after drinking large amounts of water during a race
should go the hospital and doctors should check blood sodium levels.
Annals of Internal Medicine 2000;132:711-714