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Wilderness Environ Med. 2015 Mar;26(1):59-61. doi: 10.1016/j.wem.2014.07.010. Epub 2014 Oct 14.

Exercise-associated hyponatremic encephalopathy in an endurance open water swimmer.

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Department of Emergency Medicine, St. John of God Murdoch Hospital and University of Notre Dame, Murdoch (Dr Rogers). Electronic address:
Department of Emergency Medicine, Fremantle Hospital, Fremantle (Dr Grainger).
Department of Emergency Medicine, Fremantle Hospital and University of Western Australia, Fremantle (Dr Nagree), Western Australia, Australia.


Exercise-associated hyponatremia and its more serious form, known as exercise-associated hyponatremic encephalopathy, are recognized as some of the most important medical problems seen in a variety of different forms of endurance exercise. We describe a case of exercise-associated hyponatremic encephalopathy presenting as altered conscious state and seizures in a woman who had completed a 20-km open ocean swim. Her serum sodium measured approximately 1 hour after her seizure was 119 mmol/L on point-of-care testing. With ongoing critical care support and the use of hypertonic saline, she was able to be extubated the next day, neurologically intact, and ultimately was discharged from hospital without neurological sequelae. This case emphasizes both the importance of considering exercise-associated hyponatremic encephalopathy as a cause of neurological impairment in all athletes and the pivotal role of hypertonic saline in the treatment of this condition.


exercise; hyponatremia; open water swimming

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