Heat-Related Illness

HEAT-RELATED ILLNESS

Extremes of heat and cold are part and parcel of a long-term survival scenario. In long-term survival settings or even in normal times, you may find yourself without shelter to protect you from the elements.  If you don’t take the weather into account, you have made it your enemy; it’ll be something you regret very quickly.

In the heat of summer, you might encounter someone suffering from the ill effects of overheating, otherwise known as hyperthermia.  Even in cold weather, significant physical exertion in an over-dressed and under-hydrated individual could be life-threatening.

Heat-related illness runs the spectrum from simple muscle cramps to shock. If mild to moderate, the condition is referred to as “heat exhaustion”. If severe, “heat stroke”. Heat exhaustion usually does not result in permanent damage, but heat stroke does; indeed, it can permanently disable or even kill its victim.  The effects of very high body core temperatures constitute a medical emergency that must be diagnosed and treated promptly.

The risk of heat stroke correlates strongly to the “heat index”, a measurement of the effects of air temperature combined with high humidity.  Above 60% relative humidity, loss of heat by perspiration is impaired, increasing the risk of hyperthermia.  Exposure to full sun increases the reported heat index by as much as 10-15 degrees F. In other words, the equivalent of being out in much hotter weather.

Simply having muscle cramps or a fainting spell does not necessarily signify a major heat-related medical event. You will see “heat cramps” often in children that have been running around on a hot day.  Getting them out of the sun, massaging the affected muscles, and providing hydration will usually resolve the problem.

A significant rise in the body’s core temperature is required to make the diagnosis of heat exhaustion. As many heat-related symptoms mimic other conditions, you should include an accurate thermometer as part of your medical supplies.

In addition to muscle cramps and/or fainting, heat exhaustion is characterized by:

• Confusion
• Rapid pulse
• Flushing
• Profuse sweating
• Nausea and Vomiting
• Headache
• Temperature elevation up to 105 degrees F

If no action is taken to cool the victim, heat stroke may ensue. Heat stroke, in addition to all the possible signs and symptoms of heat exhaustion, will manifest as loss of consciousness, seizures, or even bleeding (seen in the urine or vomit).  Breathing becomes rapid and shallow. You’ll notice that the skin turns red, not necessarily because it is burned, but because the blood vessels are dilating in an effort to dissipate some of the heat.

The skin will likely be hot to the touch, but in some circumstances, the patient’s skin may actually seem cool.  A person in shock may feel “cold and clammy”, but it’s important to realize that it is the body core temperature that is elevated. Taking a reading with your thermometer will reveal the patient’s true status.

Heat stroke differs from heat exhaustion in that sweating might be absent. This is a significant change, as the body uses sweating as a mechanism to cool itself down. Once the core reaches a temperature of about 106 degrees, thermoregulation breaks down and the body’s ability to use sweating as a natural temperature regulator fails. In heat stroke, the body core can rise to 110 degrees Fahrenheit or more. If not dealt with quickly, expect shock and organ failure, with death as the final outcome.

When overheated patients are no longer able to cool themselves, it is up to their rescuers to do the job. If hyperthermia is suspected, the victim should immediately:

• Be removed from the heat source (for example, the sun).
• Have their clothing removed.
• Be drenched with cool water (or ice, if available).
• Have their legs elevated above the level of their heart (the shock position).
• Be fanned or otherwise ventilated to help with heat evaporation.
• Have moist cold compresses placed in the neck, armpit and groin areas.

Why the neck, armpit and groin? Major blood vessels pass close to the skin in these areas, and you will more efficiently cool the body core. In the wilderness, immersion in a cold stream may be all you have in terms of a cooling strategy. This is a worthwhile option as long as you are closely monitoring your patient.

Oral rehydration is useful to replace fluids lost, but only if the patient is awake and alert. If your patient has altered mental status, fluids may enter their airways. This is called “aspiration” and makes the situation much worse.

You might think that acetaminophen or ibuprofen could help to lower temperatures, but this is actually not the case.  These medications are meant to lower fevers caused by an infection, and they don’t work as well if the fever was not caused by one.

Hyperthermia is largely preventable with some planning. Wear clothing appropriate for the weather.  Tightly swaddling an infant with blankets, simply because that is “what’s done” with a baby, is a recipe for disaster in hot weather. Have everyone wear a head covering. A bandanna soaked in water, for example, would be effective against the heat. Much of the sweating we do comes from our face and head, so towel off frequently to aid in heat evaporation.

If you can avoid dehydration, you will likely avoid heat exhaustion or heat stroke. Work or exercise in hot weather (especially by someone in poor physical condition) will easily cause a person to lose body water content.  Consider at least a pint or two of fluids (preferably Gatorade or another electrolyte-rich product) per hour while working in the sun. Keep a close eye on the elderly, who are at high risk for heat-related illness.

Carefully planning your outdoor work in the summer heat and keeping up with fluids will be a major step in keeping healthy and avoiding heat-related illness.  Monitor the workload (and the workers) and you’ll stay out of trouble.

Joe Alton MD

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