A near-fatal case of exercise-associated hyponatremia

A 42-year-old woman presented to our emergency department with headache, nausea, and confusion after completing an Ironman triathlon. She performed the race at a slow pace, in hot and dry weather. The first medical examination reported confusion with a Glasgow Coma Scale score of 13. A few minutes later, she presented with seizures. A cerebral computed tomographic (CT) scan showed major cerebral edema. Blood analysis showed severe acute hyponatremia (123 mEq/L) with hypotonicity (255 mEq/L). Her clinical condition quickly worsened, leading to a Glasgow Coma Scale score of 3 with fixed dilated pupils. After intubation and mechanical ventilation, she was transferred to the intensive care unit. A transcranial Doppler ultrasonography (TCD) showed intracranial hypertension signs motivating emergency osmotherapy by infusion of 20% mannitol over 15 minutes. To guide the therapeutics, an intracranial pressure monitoring was inserted, showing a value of 30 mm Hg. A few minutes later, intracranial pressure (ICP) increased to 68 mm Hg with a low cerebral perfusion pressure. Concomitantly, another TCD reported critical flows with poor cerebral perfusion. A second infusion of mannitol led to an ICP lowering and a decrease in pupil size after 10 minutes. During the next hours, the patient stayed stable without further intervention. Sixteen hours later, natremia was normal, mainly due to hyperdiuresis. On day 2, the tracheal tube was removed. A cerebral CT scan showed disappearance of cerebral edema. One month later, the patient had good recovery apart from some residual memory problems. Six months later, she was able to come back to work.