Walking Well: Heat

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Heat illness is quite common, causing from 250 to 1,700 deaths annually in the US. Usually it is classified into two types: heat stroke and heat exhaustion, as in this table adapted from the Merck Manual.

Heat Stroke

Cause Failure of heat-loss mechanism

Warnings Headache, weakness, sudden loss of consciousness

Appearance & signs Hot, red skin; sweating, high temperature, rapid pulse

Management Emergency cooling with; cold water or ice; hospitalize

Heat Exhaustion

Cause Excessive fluid loss leading to shock

Warnings Weakness, nausea, anxiety, much sweating, fainting

Appearance & signs Pale, grayish, clammy skin; weak, slow pulse, low blood pressure, faintness

Management Treat for fainting: head down, replace lost salt and water

This oversimplifies what usually occurs clinically because of other factors such as in this case. Wilderness diagnosis is difficult even for an expert and can only be resolved with reliable clinical data (body temperature, blood pressure, skin appearance, sweating, etc.).

The main heat dangers are:

Temperature: above 90 degrees F
Humidity: above 80 percent relative humidity
Sunlight: full or partial
Exertion: amount, duration and intensity of effort

Other factors contribute, including many kinds of drugs, heavy clothing, and lack of acclimatization.

Prevention is our main concern. Don't hike in extreme heat and especially humidity. Certainly don't overexert in adverse conditions. Pay careful attention to early signs. I recall developing dry mouth, fever, and fatigue (weakness) while leading a group in hot weather. I was out of water so I borrowed and drank some. This promptly abolished the symptoms. I determined never to run out of water in hot weather and routinely carry Gatorade in those situations.

Heat cramps are an important sign of electrolyte depletion. I came into the Nantahala Outdoor Center in Wesser after a hot day and tried to write in my journal. My fingers were in spasm and I could not hold a pen. I put a teaspoonful of salt in a glass of water, drank it, and within three to four minutes the spasms were gone.

What can we learn from this case? We do not know the exact sequence of events, lacking the relevant clinical observations. Crowe probably could not have foreseen the outcome since he was apparently not aware of his heart condition and was confident of his physical ability. The fact that his problems came on very gradually emphasizes that we should be very attentive to even moderate signs of heat illness. As with athletes, we should pay close attention to what our bodies are telling us. Thus I suggest that hikers read up on key subjects such as this one in a good first aid manual before starting out on the trail. Taking a wilderness first aid course is an even better option.