BIKE: Hydration can be fatal

[Patrick Goetz]

http://www.nytimes.com/2005/04/14/opinion/14thu2.html?th&emc=th


Brain-Dead From Sports Drinks
Published: April 14, 2005

For years now, we've been hearing about the importance of hydration to 
avoid heat stroke during prolonged exercise in hot weather. Now, it 
turns out, too much hydration can kill you.

A study published today in The New England Journal of Medicine should 
give weekend warriors reason to rethink the wisdom of quaffing vast 
amounts of water or sports drinks while exercising vigorously - at least 
if they are engaging in such endurance tests as a marathon. The study 
found that a marathon runner could dangerously dilute the blood with an 
overdose of liquids, risking a coma and even death. The problem has also 
been detected during long military maneuvers, extended bike rides and 
blistering hikes through the desert.

An article by Gina Kolata in The Times today describes the slow and 
belated recognition of the problem. A South African expert who has been 
warning of the dangers for more than two decades told Ms. Kolata that he 
had not found a single case when an athlete had died from dehydration in 
a competitive race, but that some people had sickened and died from 
drinking too much. Typically, an overdose of water dilutes their blood 
and reduces the concentration of sodium. Water enters the cells, causing 
them to swell, and engorged brain cells press into the skull; such 
pressure can lead to confusion, seizures and a loss of vital functions.

All too often, friends, coaches or emergency personnel assume that the 
problem is dehydration and administer yet more liquid, making the 
problem worse. The best treatment is a small volume of a concentrated 
salt solution, given intravenously, to increase blood sodium 
concentrations. Sports drinks containing electrolytes may not help much 
as they are mostly liquid themselves.

In the 2002 Boston Marathon, for example, a 28-year-old woman found 
herself exhausted after running for five hours and gulping sports drinks 
along the way. Wrongly assuming that she was dehydrated, she chugged 
down 16 more ounces of a sports drink. She promptly collapsed and was 
later declared brain-dead. The concentration of salt in her blood was 
found to be lethally low.

In the study published today, researchers at various Harvard-affiliated 
institutions tested 488 of the nearly 15,000 runners who completed the 
2002 Boston Marathon. They found that 13 percent had blood with 
abnormally low sodium levels, and that three runners were in danger of 
dying. It was not the elite runners who were at risk - it was those who 
had taken four hours or more to finish the race, allowing plenty of time 
to imbibe excess fluid.

Sports authorities have already issued warnings and tips to avoid 
excessive drinking, and rescue workers in the Grand Canyon now carry 
devices to test collapsed hikers for low blood sodium. But the solution 
is for overly eager endurance runners and hikers to forget the old 
mantra that they should drink-drink-drink. Too much liquid can be lethal.