Hyponatremia in recreational hikers in Grand Canyon National Park

Symptomatic hyponatremia has been reported in athletes participating in marathon and ultra-marathon events. We report four cases of symptomatic hyponatremia in hikers in the Grand Canyon. These are the first cases reported in recreational hikers in a wilderness setting. The overall fluid status of these patients is not well defined. In most instances this probably represents dilutional hyponatremia from sweat loss replaced with plain water. Recreational wilderness participants may require electrolyte replacement similar to endurance athletes.