Article from April, 2011


Explorers in the field are quite goal-oriented, often with a fixed time to complete the mission. Tromping through jungles, scaling narrow ledges, or seaborne on the open ocean, we are exposed to the elements while enduring physical exertion. In the excitement of the adventure, we tend to forget or ignore that we generate significant heat, which if not dissipated can lead to serious injury or possibly death.

It is critical to recognize heat illness and be prepared to respond rapidly and efficiently. Our metabolism requires a very narrow temperature range for the billions of chemical reactions of basic daily function. Even at rest, our body generates enough heat to raise our core temperature 2.5ºF per hour and strenuous activity can increase that 15 times. We release heat through our skin to the cooler atmosphere but this process slows as the ambient temperature increases toward the 95ºF of skin temperature.

As the external temperature increases and heat loss through skin decreases, sweat glands spread a layer of water on the skin surface, which evaporates and releases heat. Higher temperatures speed up evaporation, but this highly effective cooling system requires a constant source of water. Yet this system is limited because the higher the humidity, the less sweating can release its moisture into the more highly saturated air. The two obvious environments that tax the cooling system are the desert, where high heat and low humidity require greater water intake because of rapid sweat evaporation, and the jungle, where high heat and humidity make sweating relatively less effective (though profuse!).

Other less obvious environments can also be treacherous for heat regulation, such as high altitude, where significantly less humidity than at ground level increases evaporation, and higher oxygen demands cause the body to work harder. In fact, any circumstance of significant exertion even in an optimal environment can cause problems with heat regulation. Studies of exertional heat-related injuries estimate that nearly 55,000 people were treated in U.S. emergency rooms over the decade from 1997–2006. Those particularly vulnerable are the young, the elderly, and people with chronic diseases. Other factors that predispose people to serious heat illness are alcohol and drug use and poor fitness level. The body loses at least 2 liters of water per day in daily maintenance and on a hot day, even at rest, you can use 5 liters.

Activities like hiking can use an additional liter per hour, so it is essential to replace this water loss. If water is not replaced or cannot evaporate, core body temperature rises, leading to a spectrum of heat illnesses. These indications of impending trouble are gradual in onset and commonly occur in the field for other reasons, so it is important to have a high index of suspicion for heat illness. As our body tries to compensate, signs and symptoms of heat exhaustion may begin. The hallmarks of heat exhaustion are a rapid weak pulse, dizziness, nausea, headache, diarrhea, and mild temperature elevation. Some confusion or irrational behavior may manifest. It is very important to know that sweating may be either present or absent and skin of the patient may feel cool to the touch.

Heat stroke is more severe and life-threatening. Heat stroke manifests as extreme confusion, diarrhea, vomiting, dark urine, shortness of breath, bleeding, low blood pressure or shock,seizures, or unconsciousness. The failure of multiple organs is the ultimate cause of mortality, and heat stroke recovery may leave the victim with mental or physical deficits. Currently, heat stroke remains a more preventable than treatable condition. The most important component of treatment is rapid lowering of the core temperature. Oral thermometers do not reliably reflect core temperature, so a rectal thermometer is needed to monitor progress.


• Get the victim to lie down in a shaded area.

• Remove or at least loosen clothing.

• If oral fluids can be taken, encourage intake of water or electrolyte solution. Try to get a liter or two into the victim over the first few hours.

• Wet the victim down and fan vigorously if possible. Use ice packs for the armpits, groin, or around the neck.

• Rectal temperatures should be taken frequently in the initial phase of treatment to avoid overcooling. Once cooled near normal body temperature, be sure to monitor the temperature every half hour or so for the next few hours, as there can be a rebound temperature rise requiring more cooling procedures.

• Restrict all activities that day and monitor closely for recurrence the next day.

• Evacuate suspected heat stroke victims rapidly.


• Do not give oral liquids unless the victim is awake and can swallow upon command. an uncooperative or confused person may choke.

• Do not use aspirin, acetaminophen (Tylenol), antihistamines, antipsychotic drugs, or amphetamines. These all have detrimental effects on a patient in this condition.

Remember, if you can’t stand the heat, you better get out of the kitchen!

This article was published in The Explorers Journal


The Official Quarterly Of The Explorers Club Since 1921
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