Sodium status of collapsed marathon runners

Recommendations for prevention and treatment of medical emergencies in participants in marathon races center on maintenance of adequate hydration status and administration of fluids. Recently, new recommendations for fluid replacement for marathon runners were promulgated by medical and athletic societies. These new guidelines encourage runners to drink ad libitum between 400 and 800 mL/h as opposed to the previous "as much as possible" advice. To assess the sodium and hydration (plasma osmolality) status of collapsed marathon runners after the promulgation of new hydration guidelines. Plasma sodium and osmolality values of runners who presented to the medical tent at the finish line of the 2003 Boston Marathon were measured. Using reference ranges derived from the general population, of 140 collapsed runners, 35 (25%) were hypernatremic (sodium, >146 mEq/L) and 6 (12%) were hyperosmolar (osmolality, >296 mOsm/kg H(2)O), whereas 9 (6%) were hyponatremic (sodium,