Summer heat - it can kill you if you are not careful

Thomas Secrest's picture
Your brain in the sun: Photo by Thomas Secrest

As I write this, temperatures around Phoenix are between 105 and 116 F. In parts of southern California temperatures are expected to reach into the middle 120s today.

These are the kinds of temperatures that can kill you. Your body has only one real mechanism for ridding itself of excess heat and that is through sweating. By putting water on the surface of your body and then having the water convert to water vapor removes a great deal of heat. But there is a limit to the efficiency of this mechanism. One limiting factor is the amount of water in your body that can be spared for heat removal. Another factor is how much fat you carry in your dermis. The fat under your skin is like having a blanket around your body. Not the best of ideas on hot days. And lastly, your age and health determine how well you can cope with high temperatures.

At extreme temperatures, your body must be adapted in order to survive. In the U.S. we live in a well air conditioned environment, and for most, our body has never become adapted for extreme heat. Therefore when extreme heat arrives, we need to be extremely cautious, because an unadapted body won’t be able to handle the heat, no matter how much water you drink.

What is the difference between heat exhaustion and heat stroke?

Heat exhaustion

As I mentioned above, your body tries to cool itself through sweating. As the ambient temperature increases your body starts to sweat. Your body is constantly making heat and the cool air around you acts as a heat sink that helps keep your temperature at 98.6 F. Because we really can’t stop producing heat and because we are well insulated, the ambient temperature at which our body can balance its heat loss and heat production is well below 98.6. I start sweating when the ambient temperature is in the 70s and if I am doing something physical, sweating can easily take place in the 50s. When the ambient temperature reaches 98.6 F, most people are sweating profusely. At 98.6 the air and our skin come into thermal equilibrium. This basically means convective heat flow is equal in both directions i.e. heat flow from air to skin and from skin to air. You sweat heavily (evaporation heat loss) when the ambient temperature is at 98.6 because you are producing heat faster than you can transfer it to the environment through radiation, conduction, and convection. Recall that heat flows from areas of high heat to areas of low heat; therefore, after the ambient temperature goes above body temperature, the air begins to transfer heat to your body and you have to sweat even more to compensate for it. The key, you now realize is sweating. If you can sweat enough you can do an amazing job at cooling yourself, even when temperatures are well over 100 F. However strange it may sound, sweating takes training. Someone who is well conditioned can go out and play football in the summer time. If someone who is not conditioned tries it, there is a chance they could die. In general, most people are not well conditioned to cool themselves in the summer. It means their bodies just can’t produce enough sweat to keep the body cool even if you drink lots of water. Additionally, there are physiologic changes that must take place, and they don’t happen overnight. If you are not adapted to the heat, your inability to sweat enough to cool your body leads to a rising body temperature. As the temperature climbs toward 104 F the following symptoms will start to appear:

• Muscle cramping (heat cramps) these are often the first signs of hyperthermia; failure to treat at this point may lead to heat exhaustion

Symptoms of Heat exhaustion:

• Cool, moist skin
• Profuse sweating
• Feeling faint
• Feeling dizzy
• Headache
• Rapid pulse
• Falling blood pressure, especially when standing or when standing up
• Nausea

All these symptoms are side effects of sweating, loss of electrolytes and the body trying to cool itself by shunting blood from the core of the body to the extremities.

Heat exhaustion is serious, but is not considered life threatening. However, the transition between heat exhaustion and heat stroke, which is a life threatening medical emergency, can be swift and subtle.

Treatment of heat exhaustion:

• Stop physical activity (activity generates internal heat)
• Rest in a cool place (remember, when temperatures are over 100 F, there are no cool places outside)
• Cool the body with water (cool areas with high blood flow e.g. neck, face, head, arm pits, wrists)
• Increasing air flow over the body, especially in conjunction with cool water, can rapidly reduce body temperatures.
• Drink fluids to replace those lost during sweating (do not drink alcoholic beverages)
• Remove any clothing acting as an insulator, the body needs to radiate heat as much as possible


Heat Stroke

As I mentioned above, heat stoke is a medical emergency. As the body temperature climbs steadily, the bodies thermoregulatory system will start to fail. When this happens, the body temperature will begin to increase even faster. Temperatures over 104 F can cause brain damage and if not reversed are fatal. The period of time a person can withstand these temperatures varies from person to person.

Symptoms of a heat stroke include:

• Body temperature over 104 F
• Lack of sweating with warm, dry skin (this is a critical sign of failure of the thermoregulatory system)
• Continued or new muscle cramping (due to loss of electrolytes)
• Headache
• Confusion or unconsciousness
• Very rapid heart rate
• Panting (rapid breathing)
• Skin feels warm and looks flushed


Remember, heat stroke is a medical emergency and required aggressive, immediate treatment.

• Call 911
• Get the victim into water or spray them with water or get them and keep them as wet as possible
• Air flow is very important, once the victim is wet start to fan them with whatever is available. The increased air flow combine with water evaporation is a powerful cooling mechanism.
• Apply ice to the head, neck, armpits, groin, back of knees and front of wrists.
• Be very careful to monitor for shivering or other indications that the victim feels cold. Recall that the thermoregulatory system has failed and the rapid cooling of the body may trigger shivering. Shivering can generate a tremendous amount of internal heat and must be avoided. Even without shivering, if the victim reports feeling cold you should moderate your cooling methods. It is important to avoid generalized vasoconstriction from cold, which will redirect blood flow away from the skin and toward the body core, in effect, conserving body heat.
• Remember, the victim may be confused and uncooperative, you must be persistent.

Who is at risk?

Generally, the young and the old are most at risk of heat exhaustion and heat stroke. Their bodies are least able to handle the cooling requirements of high temperatures and they are least able to handle the physiologic stress of high temperatures. Babies in particular have immature thermoregulatory systems and can become hyperthermic very quickly.

So this summer, be careful, stay informed about high temperatures. Remember that black top parking lots and city centers can be well above the forecast high and the inside of a car can reach the 150s in just a matter of minutes, when in direct sun. Stay hydrated, but don’t drink alcohol. Drink fluids like Gatorade to replace electrolytes. If you’re going to be out in the heat, wet your shirt and hat often to help your body cool itself. On days when the humidity is over 75% sweating becomes ineffective; this means you have to be extra careful, since you will overheat much faster. If you feel yourself starting to overheat, take steps quickly to reverse the process. When it comes to heat, never was there a truer saying than ‘a stitch in time saves nine.’

This summer, play it safe, play it cool. Know the warning signs of hyperthermia and stop it in its tracks BEFORE it stops you.

Dogs get heat stroke too

Please don’t forget about the family pet. Dogs are no more adapted for the heat than most people. All the warnings mentioned above also apply to dogs. Dogs can’t tell you they are feeling ill and their eagerness to be around you means they will push themselves beyond their limits. You've got to think for them, since they can’t think for themselves.

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