Marathon runner's death linked to excessive fluid intake

By Stephen Smith, Globe Staff, 8/13/2002

The 28-year-old runner who collapsed and died in this year's Boston Marathon was felled by a precipitous cascade of medical events brought on in part by drinking too much fluid, the state medical examiner's office concluded yesterday.

Cynthia Lucero, who in the week before the April marathon completed her doctoral dissertation on how marathons help runners grieve, died from a condition known as hyponatremic encephalopathy, which happens when the brain becomes swollen because of a critical imbalance of sodium. She was only the second runner to die in the 106-year history of the race.

''This is a relatively rare catastrophic complication,'' said Dr. Ronenn Roubenoff, associate professor of medicine and nutrition and director of human studies at the Jean Mayer USDA Human Nutrition Research Center at Tufts University. ''It really is a tragedy because it's such a preventable thing.''

For the neighborhood jogger taking to the baking pavement in the August heat, the death of Lucero provides a graphic illustration of the dangers of drinking too much water or even sports drinks. Runners have long known the importance of replenishing fluids, but they may not know that it is also vital to maintain a balance in sodium levels to keep cells healthy. If runners drink too much fluid, they can dangerously dilute their blood sodium levels.

That condition is called hyponatremia. Although people seldom die from hyponatremic encephalopathy, health-threatening sodium deficiencies are more common among athletes than doctors once believed. Roubenoff cites one study, for example, that tracked 18,000 marathoners and found that among those seeking medical care after the race, 9 percent suffered from the condition. Deaths are sufficiently rare that specialists can recount them individually.

Until recently, hyponatremia was a little-known, even less-understood medical condition. But researchers, including Dr. Arthur J. Siegel of McLean Hospital, are learning more about hyponatremia, known more commonly as water intoxication.

Siegel is deeply familiar with Lucero's case, having obtained with her parents' permission a blood sample drawn at Brigham and Women's Hospital, where the runner was taken after she collapsed. He and other scientists are hopeful that, in death, Lucero will yield medical evidence that can prevent other runners from the fate that befell her.

''We want as Cynthia's legacy a better understanding of this problem so that we can work out strategies to make it less likely that these cases will happen in the future,'' said Siegel, director of internal medicine at McLean.

The 2002 Boston race was Lucero's second marathon. The previous one was two years earlier in San Diego, a race she completed in about 41/2 hours. She was running the Boston Marathon to raise money for the Massachusetts chapter of the Leukemia and Lymphoma Society.

On that April Monday, friends tracked her progress. They said that Lucero, wearing bib number 15,611, drank large amounts of Gatorade and looked well as she loped through the bottom of Heartbreak Hill in Newton, about six miles from the finish.

But with Cleveland Circle in sight, Lucero began to falter, those friends recalled. One of them hopped into the race next to her and Lucero told the friend that she felt dehydrated and rubber-legged. Lucero tumbled to the pavement. When she reached Brigham and Women's, she was comatose.

Lucero's parents, who'd traveled from Ecuador to mark the completion of her dissertation, had been waiting at the finish line.

The precise causes of the syndrome that killed Lucero remain somewhat mysterious, and dispute persists among researchers over whether the predominant triggering mechanism is related to too much fluid or extreme dehydration. Increasingly, though, scientists believe that the problem transcends a simple equation of too much or too little water.

They believe it's vastly more complex. Siegel and other researchers theorize that marathoners, triathletes, and other athletes who engage in extreme sporting competition often deplete the fuel that powers the body's cells. When this happens, a hormone called arginine vasopressin gets released. Part of its function is to tell the kidneys to hold on to fluids.

That, in turn, precipitates an imbalance in sodium levels in the blood. But as salt drops in the blood, it does not do so in cells. The body, in its constant pursuit of equilibrium, attempts to force salt out of cells by flooding them. That causes swelling. Muscles can endure such swelling because they can bulge outward. The brain, though, cannot.

''The brain lives in a box - the skull - and it doesn't have anywhere to go when this swelling starts,'' Roubenoff said.

Lucero's death showed that even runners who drink sodium-laden sports drinks remain at risk of the condition, which Siegel cites as evidence that the syndrome is more complicated than simply taking in too much fluid. That is why he and people who organize races are working on ways to improve measures of runners' health, including weighing them before and after races to make sure they haven't lost too much fluid or, conversely, consumed too much.

''We are moving toward understanding this problem,'' Siegel said, ''and if we can make some headway, maybe we can prevent more losses like Cynthia's.''

Stephen Smith can be reached at stsmith@globe.com.

This story ran on page A1 of the Boston Globe on 8/13/2002.
) Copyright 2002 Globe Newspaper Company.