What does extreme heat do to the human body?

By Tyler Losier, AccuWeather staff writer

Summer is quickly approaching, which means millions of people across the country are once again filling swimming pools and cranking up air conditioning units to help deal with the hot weather.

As most people already know, extreme heat can be rather uncomfortable. But what actually happens to the human body as the mercury rises?

“Your body absorbs heat from the environment, and as your temperature starts to rise, your body will naturally do a number of things to get rid of that excessive heat,” said Dr. Peter Shearer, an emergency medicine expert at The Mount Sinai Hospital in New York. “As you get up to higher levels of body temperature, or prolonged exposure, your body may lose that ability.”

According to the Mayo Clinic, the most serious level of temperature dysregulation is called heat stroke, and it occurs when the body’s temperature reaches an excess of 104 degrees Fahrenheit.

During heat stroke, body functions grind to a halt, as the hypothalamus region of the brain shuts down the body’s natural coolant system, perspiration. Without sweat, the body can no longer keep its temperature in check, which causes a devastating chain reaction that can be fatal without timely medical intervention.

Heat Infographic Updated

Original illustration by Dorling Kindersley/Getty Images

From a neurological standpoint, heat stroke causes the brain to swell, leading to headaches and even seizures in more extreme cases. Victims also experience an altered level of consciousness, including confusion, delirium, hallucinations, agitation and even unconsciousness.

The cardiovascular system is affected as well. Heat stroke causes blood pressure to drop and the heart to beat faster and more irregularly, heightening the risk for high-output cardiac failure. Small blood clots can also form in blood vessels, preventing healthy circulation and cutting off blood flow to other parts of the body.

With regards to the renal system, heat stroke decreases urine output and causes a condition known as acute tubular necrosis, in which the kidneys fail to receive enough oxygenated blood to support proper function. If untreated, heat stroke can eventually cause the kidneys to fail.

“This is why people sometimes die during heat waves,” Shearer said. “They can lead to devastating injury.”

Shearer also warned about the dangers of high humidity.

“A 94-degree day in Arizona is different than a 94-degree day in southern Georgia,” he said. “When there’s an increase in humidity, your body’s ability to lose heat to the environment through sweating is diminished.”

Thermometer heat wave

Heat wave (Marccophoto/Getty Images)

In addition to humidity, there are a few other factors that can exacerbate the risk of heat-related illness.

Age plays a big role in the body’s ability to regulate heat. Young children and the elderly are not only more susceptible to high temperatures due to their lower-functioning nervous systems, but they may also have more difficulty removing themselves from a hot situation.

“In a heat wave, if you’re elderly and your air conditioner is not working, your ability to go get it fixed is maybe diminished,” Shearer said. “So, you may be exposed to an extreme of heat for a longer period of time.”

Exertion is an important factor to consider as well. Strenuous exercise heightens the risk of heat stroke, especially if an individual is not used to training in hot weather.

Those with conditions such as heart or lung disease, obesity or a history of prior heat stroke are more at risk than their healthier counterparts. Other diseases that affect circulation, such as diabetes, can also be problematic. Anyone who suffers from these ailments should be watched closely in hot weather, and if they begin to show signs of heat stroke, medical attention should be rendered immediately.

Lastly, certain drugs and medications can also be a contributing factor in heat stroke. Alcohol, stimulants, vasoconstrictors, beta blockers, diuretics, anti-depressants and anti-psychotics all detract from the body’s ability to cool itself.

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Prevention of heat stroke primarily involves limiting the amount of heat that the body can absorb from the surrounding environment.

Individuals going out in the sun should wear loose-fitting, light-weight clothes, drink plenty of fluids, apply sunscreen regularly and listen to their body’s warning signs. If nausea, headaches, fatigue or any other indicators of heat illness present themselves, it’s time to go inside.

Treatment of heat stroke involves lowering a victim’s body temperature as quickly as possible.

“You want to do all the things you can to cool them down. The first would be to remove them from a hot situation, whether that be pulling them inside to a cooler place or getting them out of the sunlight into the shade,” Shearer said. “Then you’d want to help them to try to regulate better and increase any convection going past them. If you can, you would actually fan them to help blow off some excessive heat.”

Again, heat stroke is a medical emergency. It is important to dial 911 at the first sign of illness, as timely intervention can be the only thing separating life and death in many circumstances.

For more safety and preparedness tips, visit AccuWeather.com/Ready.

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