Copyright 2002
Wilderness Drum, Inc.
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The Prevention and Treatment of Heat Illness
Steve Beyer

Definitions

Heat illness or hyperthermia is what happens when you are too hot. There are two serious types of hyperthermia – heat exhaustion and heat stroke. The two conditions are points on a continuum which runs from being hot to being deathly ill. The primary difference between heat exhaustion and heat stroke is that in heat exhaustion the body’s heat dissipating mechanism has been overworked, while in heat stroke the body’s heat dissipating mechanism has been overwhelmed.

Prevention

It is important to remember that, in a wilderness setting, both heat exhaustion and heat stroke can often be prevented simply by adequate hydration. Whoever designed the human body made two major mistakes – the knee, which comes apart under even moderate lateral pressure, and the thirst mechanism. The trigger for thirst is a beginning electrolyte balance – that is, when you get thirsty, it is already too late. That is why it is important to drink lots of water in the wilderness, and to drink it before you get thirsty. Pound it down. Force yourself. Drop a tea bag in your water bottle to give the water some taste. Set up a rule that if one person drinks, everyone has to drink.

Heat exhaustion

Heat exhaustion is actually an early stage of hypovolemic shock. The body’s fluid levels have dropped sufficiently that organs are not getting enough oxygen carried to them by the blood. The fluid pressure has dropped because of a combination of excessive sweating, dilation of surface blood vessels, and inadequate water intake. Since the brain is one of the first organs affected by inadequate perfusion, one of the first signs of heat exhaustion is often a change in level of consciousness – spaciness, forgetfulness, confusion, odd speech, restlessness, anxiety, and changes in behavior, sometimes subtle. Other signs and symptoms are thirst, weakness, headache, nausea, dizziness, rapid pulse, rapid breathing, exhaustion, and profuse sweating. Patients can sweat so much that they feel cold, have goose bumps, and complain of chills. The skin is cool and pale.

The treatment for heat exhaustion is simple. Get the patient cool. Move the patient to the shade of a tree, fan her, pour water on her head. Remove heavy clothing. Have the patient lie down. If the patient is alert and able to swallow, give him water; or, if you have it, Gatorade diluted three to four times; or about a half-teaspoon of salt dissolved in a quart of water, maybe with a pinch or two of sugar. Have the patient drink as much as a quart of water over the next hour. Recovery should be rapid and without consequences. If the patient does not improve promptly, then the condition may in fact be an early stage of heat stroke, and immediate evacuation should be seriously considered.

Always suspect heat exhaustion when a person becomes ill in hot conditions, especially during physical exertion, and particularly if accompanied by changes in level of consciousness. Heat exhaustion should be treated aggressively. More important, it should be prevented by drinking lots of water in the wilderness.

Heat stroke

Heat stroke, as opposed to heat exhaustion, is a life-threatening illness that requires immediate evacuation. It has many of the same signs and symptoms as heat exhaustion, but they are more severe. There is an altered level of consciousness, rapid heart rate, and increased respiratory rate. The altered level of consciousness can be dramatic – disorientation, irritability, combativeness, delusions, incoherent speech. There can even be loss of coordination and convulsions. The patient may or may not be sweating, but will complain of being hot rather than cold. The skin is hot, red, and wet rather than pale and cool. The body’s core temperature has risen to above 105 degrees. It will be obvious that something is very wrong.

The treatment for heat stroke is the same as the treatment for heat exhaustion. Cool the patient off as rapidly as possible. Remove heavy clothing. Cover her with wet cotton clothing and fan her vigorously. Apply ice if it is available, and at least pour the coldest available water over her. Concentrate on cooling the head and neck. It is probably not a good idea to try to immerse the patient in a river or stream, because a disoriented, combative, or convulsing patient is hard to manage and may drown. Do not delay. Be aggressive. You are saving her life. Cardiovascular and neurologic collapse are imminent. Evacuate immediately, and continue cooling procedures during evacuation.

A few other points. Keep good records of vital signs, especially body temperature. The temperature may go down during cooling, and then rise again when you have stopped active cooling measures. If the patient becomes unresponsive, pay particular attention to keeping an open airway. If shock occurs, elevate the patient’s legs twelve inches.

Is it possible to cool off a hyperthermic patient too fast?

In the wilderness, I do not think that cooling off a heat stroke victim too fast is a problem; more likely the problem will be trying to figure out how to cool him off fast enough. I generally do not pack ice into the wilderness; those little squeeze bags for cooling off orthopedic injuries, if you have packed them in, do not generate a lot of cold. And remember: your heat stroke patient is, literally, dying. As his core temperature continues to rise, vital organs, such as the brain and kidneys, start to shut down. I believe that the risk posed by the heat illness is much more immediate than the risk of inducing some kind of cardiac arrhythmia or hypothermia. As always, judgment is important, and the patient’s temperature should be as carefully monitored as possible. Remember that cooling may be effective in lowering body temperature, but the temperature may rise again when cooling efforts cease.

Can you drink too much water?

It is, theoretically, possible to drink too much water and die. The problem would be that water, in sufficient quantities, could dilute the necessary electrolytes in the blood to the point where organ systems would start to shut down, especially if electrolyte levels have already been depleted by sweating. Hyponatremia, or too little sodium in the blood, is defined as a blood sodium concentration of less than the normal range of about 136-143 mmol/L (as always, healthy individuals can vary somewhat from the norm). Symptoms of hyponatremia appear in stages – weakness, disorientation, seizures, and coma if the condition is not reversed. However, I believe the condition is unlikely to occur in the wilderness setting, and, certainly, fear of drinking too much water should never keep people from adequately hydrating themselves. Studies of marathon runners and other people who exercise in the heat, sweat out lots of sodium, and drink lots of water – in one study, two gallons during six hours of exercise – do not show significantly lowered sodium concentrations. One study showed normal electrolyte balances maintained when subjects consumed only 30 percent as much potassium as they normally would while losing three to four liters of sweat daily for eight consecutive days. The few reported cases of hyponatremia have apparently been in ultra-marathon runners, whose physiology becomes weird anyway, and do not, I believe, indicate a risk during normal or even extreme wilderness activity. So keep pounding down that water.

Bear in mind that I am talking about wilderness emergency care, or care where resources are extremely limited – no ice, no normal saline, no IV start kit, no ambulance, no hospital. I will defer to others about urban street medicine, or patient management where such resources are readily available.

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