Case Report
Hiker Fatality From Severe Hyponatremia in Grand Canyon National Park

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We present the case of a hiker who died of severe hyponatremia at Grand Canyon National Park. The woman collapsed on the rim shortly after finishing a 5-hour hike into the Canyon during which she was reported to have consumed large quantities of water. First responders transported her to the nearest hospital. En route, she became unresponsive, and subsequent treatment included intravenous normal saline. Imaging and laboratory data at the hospital confirmed hypervolemic hyponatremia with encephalopathy. She never regained consciousness and died of severe cerebral edema less than 24 hours later. We believe this is the first report of a fatality due to acute hyponatremia associated with hiking in a wilderness setting. This case demonstrates the typical pathophysiology, which includes overconsumption of fluids, and demonstrates the challenges of diagnosis and the importance of appropriate acute management. Current treatment guidelines indicate that symptomatic exercise-associated hyponatremia should be acutely managed with hypertonic saline and can be done so without concern over central pontine myelinolysis, whereas treatment with high volumes of isotonic fluids may delay recovery and has even resulted in deaths.

Introduction

Exercise-associated hyponatremia (EAH) has been long recognized as a possible complication of endurance exercise that can have a fatal outcome.1, 2, 3, 4, 5 The first documented EAH death was of a marathoner in 1993,4 and EAH has also been identified as a potential problem among hikers for more than 2 decades.6, 7, 8, 9, 10, 11, 12, 13, 14 As far as we are aware, the present report is the first documented fatal case of EAH in a hiker. We share this case because proper initial management of EAH can be critical to the outcome, and there is evidence that current treatment guidelines for EAH have yet to be universally adopted.9, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

Section snippets

Case presentation

On September 3, 2008, a previously healthy 47-year-old woman from London, England, hiked for approximately 10 km on the South Kaibab Trail in Grand Canyon National Park, descending and then ascending roughly 900 m in elevation over a 5-hour period. The day was clear and sunny. Temperatures were near 10°C at the start of the hike at approximately 0800 hours, and 26.6°C at the end of the hike near 1300 hours. During the hike, her husband reported she “drank a large amount of water and ate very

Discussion

Exercise-associated hyponatremia is a potentially serious condition that is now generally known to be due to overhydration in combination with fluid retention from nonosmotic stimulation of arginine vasopressin (AVP) secretion.25, 26 Nonosmotic stimuli for secretion of AVP include intense exercise, nausea or vomiting, hypoglycemia, and nonspecific stresses such as pain and emotion.27, 28, 29 Excessive losses of urine sodium due to secretion of brain natriuretic peptide may also contribute to

Acknowledgments

This work was supported by the resources and use of facilities of the Grand Canyon National Park Preventive Search and Rescue Team, Grand Canyon Clinic North Country Community Healthcare, and the VA Northern California Health Care System.

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