Summer, salt and sun

There is a true story that gets circulated among those interested in wilderness medicine of three elderly women who set out on a guided trip down the Colorado river in the Grand Canyon, along with about a dozen other passengers. As expected, they were counseled on the risks of dehydration in the arid desert environment. As the story goes, all the women followed instructions to increase their fluid intake, only occasionally using an electrolyte replacement solution. Surely, they figured, more is better than less when it comes to rehydration.

Within a couple of days, each of these three women went on to develop severe symptoms including diarrhea, vomiting, confusion and disorientation, and eventually for one, severe seizures. The source of these symptoms was at first a mystery to those involved. After helicopter evacuation to the closest hospital, it was discovered that they all suffered from a severe type of under-recognized heat injury – hyponatremia, or low sodium levels.

As it turns out, there’s a lot more to heat than being hot. In the summer season, when we’re sweltering in the stands of a sports event, pouring sweat while enjoying our favorite waterway, or just cursing the heat and humidity when escaping work for a walk outside, it can be easy to forget that warmer weather can bring other conditions besides just getting overheated.

Traditional types of heat injury include simple dehydration, heat exhaustion, heat syncope (fainting) and heat stroke. All of these have some overlap of symptoms, and the mainstay of treatment consists of cooling off and providing fluids. However, as demonstrated by the story of the elderly river rafters, there is more to heat injuries than what is typically known.

Often referred to as exercise-associated hyponatremia or water toxicity, low sodium can be a life-threatening condition. Its root cause comes from ingestion of too much water without enough salt, often in conjunction with heavy exertion that causes a person to produce sweat that has a high salt concentration. The combination of these factors leads to serious depletion of sodium, and can cause confusion, vomiting and potentially fatal seizures.

It used to be believed that this particular condition only occurred in elite endurance athletes, but several case reports have revealed its presence among even the most benign of activities under the right conditions, including lawn bowling. All types of heat injury can also overlap with a condition called rhabomyolysis, which is critical breakdown of muscle tissue that can lead to kidney failure.

Your mother used to tell you that an ounce of prevention is worth a pound of cure. The adage holds true when it comes to heat illnesses as well. The best way to avoid getting hyponatremia or any of the other heat-related illnesses is to avoid overheating to begin with. It is advisable to take breaks when exercising or spending time outdoors, and find a place in the shade or indoors to cool off. Certainly, if you begin to feel faint or weak, a rest is mandatory. If you don’t feel better after resting, or if confusion develops, the situation has become critical and medical care should be sought. When judging fluid intake, it is important to drink to the level of thirst that is developed, and not more than that.

Summertime is a great time of the year to get out and enjoy everything the region offers, but it can also create conditions that might subtly cause some serious health issues. Have fun, enjoy the weather, but stay cool.

Keep in touch with the Prisma Health Blog to see more topics on wilderness and environmental medicine. This unique specialty within medicine covers topics from lightning injuries to sea anemones, and from bear attacks to bee stings.

As the Department of Emergency Medicine at Prisma Health Upstate expands, its academic offerings for wilderness medicine are expanding with it. Starting this academic year, some residents will receive formal wilderness training as part of their residency curriculum. The department will be sponsoring the area’s first Advanced Wilderness Life Support (AWLS) course for medical professionals, hosted at the USC School of Medicine Greenville Nov. 2–4. Visit for more details or to register for the course.

Post author Dr. Nathaniel Mann is an emergency medicine physician with Prisma Health. He has a special interest in wilderness medicine.

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