Following a 56-mile ride on May 18, Snyder developed hyponatremia, a potentially fatal condition that occurs when the body's sodium level gets too low. As in most cases, Snyder's problem resulted from drinking too much liquid--about six pints over 5 1/2 hours. Sensing something was wrong--she was dizzy and vomited twice after arriving home--she dialed 911. The paramedic who found her collapsed in the front yard could barely feel her pulse. "I could have been a goner," Snyder says.
Hyponatremia isn't as common as dehydration, which, in severe cases, can lead to heat stroke. But health professionals say they're seeing more cases of hyponatremia at marathons, triathlons, lengthy charity walks, and other endurance events that last four hours or more. That's because more would-be athletes are participating and following age-old advice to drink a lot to avoid dehydration.
Liquids are important. But it's easy for the sometime athlete, whose body isn't acclimated to such strenuous exertion, to overdo it. "It's critical to understand that too much liquid can have severe consequences that may be more dangerous than taking in too little fluid," says William Roberts, a White Bear Lake (Minn.) physician and medical director for the Twin Cities Marathon. While it helps to down sports drinks, such as Gatorade, that replenish some sodium, even too much of those can put you in jeopardy.
Hyponatremia occurs when the sodium level in the fluid between cells falls below the normal range of 135 to 145 milli-equivalents per liter. Sodium plays an important role in balancing the fluids between the outside and inside of cells and in retaining the right amount of water. But this balance can get dangerously out of whack when a person consumes liquids at a faster rate than the body excretes them, either through sweat or urination.
Symptoms start when cells take in more water to stay in balance with the higher water concentration in the intercellular fluid. The brain is particularly vulnerable as its cells swell and push against the skull. That's why the first signs include headaches, nausea, vomiting, and mental confusion. Too much pressure can cause seizures, setting off complications that can lead to death.
Experts say taking sports drinks during the event and adding extra salt to your food in the days before the event can help prevent hyponatremia. The best precaution, however, is to know your sweat rate and replace only the fluid you excrete (table). Many marathons and triathlons now warn contestants about drinking too much. A few events have even begun spacing water stations farther apart as a precaution.
Once symptoms start, it can take just minutes for the condition to spiral out of control. Snyder was lucky on two counts. As disoriented as she was when she entered her home, she had the presence of mind to call 911. Then, when she arrived at the hospital, the emergency room doctor correctly diagnosed hyponatremia and treated her with intravenous salt-replacement fluids.
Not every doctor might have made the right call. Warren Scott, a Soquel (Calif.) physician on the medical team of the Hawaiian Ironman Triathlon, says he has reviewed six cases in which ER docs assumed the patient was dehydrated from exertion. "The doctors worsened the situation by giving fluids to someone who was fluid-overloaded," he says. "Luckily, they realized this and were able to reverse it."
Snyder spent two days in the hospital. While she missed the charity ride, she plans to go for it next year. But next time, she'll know better than to guzzle water till she's fit to burst. By Robert Berner