Acute mental status changes following an ultramarathon

Exercise-associated hyponatraemia is an abnormally low blood sodium concentration occurring during or up to 24 hours after physical activity. It is relatively common in some activities, and has been the cause of death across a wide array of activities. Exercise-associated hyponatraemia is recognisable through patient presentation and a history consistent with excessive fluid intake, and may even occur with considerable sodium intake during the exercise or sporting event. We present a case of an ultramarathon runner who was seen post-race displaying the classic signs of exercise-associated hyponatraemia, and rapidly responded to appropriate treatment with oral 3% hypertonic saline and fluid restriction without requiring further intervention. Although 9% oral saline solution has been documented to effectively treat mild to moderate symptomatic exercise-associated hyponatraemia, this case report provides evidence that oral 3% hypertonic saline can also be effective in such cases.