Water Intoxication Case in Hiker

While emphasis is often placed on keeping athletes and outdoor enthusiasts properly hydrated, too much water can be just as dangerous. Exercise-associated hyponatremia (EAH), a form of water intoxication, results in an extreme, and potentially fatal, sodium imbalance.

In the latest issue of Wilderness & Environmental Medicine, investigators detail the case of a hiker who died as an illustration of the potential danger of endurance exercise and excessive water intake lowering serum sodium to a dangerous level. There have been several deaths from EAH associated with various sports. This is one of few reported fatalities due to EAH in a wilderness setting.

The study details the death of a 47-year-old female hiker who passed out after a 10 km hike on the South Kaibab Trail in Grand Canyon National Park in 2008. Over a five-hour period, the woman consumed a large amount of water but ate very little food. She collapsed approximately an hour after finishing the hike. Despite the efforts of emergency medical personnel, the patient was pronounced dead 19 hours later from cerebral edema brought on by water intoxication.

As outdoor endurance recreation grows in popularity, so does the risk of EAH. Early symptoms of EAH often mimic dehydration and include nausea, vomiting, malaise, and headache. If left untreated, the condition can lead to an altered mental status, seizures, and death. Unfortunately, many practitioners have difficulty recognizing the condition and treating it appropriately.

“EAH results from overhydration, and avoiding additional fluid overload is critically important in treatment,” explained co-investigator Martin D. Hoffman, MD. “Because dehydration is often a reflex diagnosis for a symptomatic exerciser in a hot environment, the usual treatment of oral or IV isotonic or hypotonic fluids needs to be resisted if there is a strong likelihood that the underlying condition is EAH.”

What can we use from this in teaching undergraduate A&P?

• When discussing fluid/electrolyte balance, we can introduce the concepts of water intoxication and EAH


• This particular case can be discussed as an example of water intoxication


• This particular case could be adapted into a case-study activity in your course—or a case-study problem on a test.


• The fact that early symptoms of EAH mimic dehydration, creates a clinical issue.  Class discussions regarding this—including suggested solutions from the research article—could be fruitful in increasing the understanding of basic principles of fluid/electrolyte balance in the body—as well as critical thinking skills.


• This is a good example of practical applications of fluid/electrolyte balance, thus answering the common question, "why do we have to learn all this?!"


• Everybody should know this, right?

Quick points about water intoxication (EAH)

EAH symptoms

• Impaired exercise performance
• Nausea and vomiting
• Headache
• Altered level of consciousness
• Seizure (convulsion)
• Muscle cell breakdown (rhabdomyolysis) with the development of acute kidney failure

NOT symptoms of neither EAH nor dehydration

• Dizziness and fainting
• Muscle cramping
• Wheezy breathing

Risk factors of EAH

• Overdrinking water, sports drinks, and other hypotonic beverages
• Weight gain during exercise
• Exercise duration of more than 4 hours
• Event inexperience or inadequate training
• Slow performance pace
• High or low body mass index
• Readily available fluids

Want to know more?

Hiker Fatality From Severe Hyponatremia in Grand Canyon National Park

• Thomas M. Myers, MD, and Martin D. Hoffman, MD. Wilderness & Environmental Medicine, Volume 26, Issue 3 (September 2015) DOI: http://dx.doi.org/10.1016/j.wem.2015.03.001
• Research article outlining the case, including causes, outcomes, and suggestions for successful diagnosis and treatment of EAH.
• my-ap.us/1h7J3Qy

Seven clear symptoms of Exercise-Associated Hyponatremia

• Timothy Noakes. Human Kinetics. Accessed 28 Sep 2015. 
• Excerpt from the book Waterlogged: The Serious Problem of Overhydration in Endurance Sports (ISBN-13: 9781450424974) Source of the symptoms "quick points" listed above.
• my-ap.us/1h7JeeJ

Guidelines Released for Exercise-Associated Hyponatremia

• Diana Phillips. Medscape Medical News. July 03, 2015
• Summary of recent guidelines published in a statement developed at this year's Third International Exercise-Associated Hyponatremia Consensus Development Conference. Source of the risk factors in the "quick points" listed above.
• my-ap.us/1P41yTN

Some text adapted from an Elsevier press release
Top photo: Sanja Gjeero
Bottom photo: Sara Hammeraback