The Dangers of Extreme Heat


Summertime in Texas means temperatures that are commonly 100 degrees or hotter. Whether you are actively exercising outdoors or cleaning out the garage on a hot weekend day, it pays to be smart about heat-related illnesses.

Timothy Jones, M.D., an emergency medicine physician on the medical staff at Baylor All Saints Medical Center at Fort Worth, answers some questions and provides some tips on recognizing heat stroke.

Q:  What is heat stroke?

Heat stroke is the most severe form of heat illness, a series of progressive conditions related to the body’s inability to deal with the heat. Heat illness begins with minor symptoms such as swelling and rash (prickly heat), and progresses to cramps, uncontrolled muscle spasms, dizziness and fainting, and ultimately heat stroke.

Heat stroke is typically defined as a body temperature greater than 106 degrees Fahrenheit, and is associated with absence of sweating and neurologic symptoms, typically unresponsiveness or severe confusion.

When a person reaches a state of heat stroke his or her body is no longer able to self-regulate temperature, and without prompt medical treatment one’s life is in peril.

Q:  What happens as a result of exposure to extreme heat?

In normal circumstances, temperature sensors in the skin, muscles and spinal column send signals to the temperature regulation part of the brain, the hypothalamus, saying, “we’re getting hot, cool us down!”

This triggers predictable behavioral and physiologic changes in the body. Thirst is stimulated, and our discomfort prompts us to seek shelter from the heat.

Meanwhile, sweat glands are stimulated, and the body dilates or enlarges capillary beds and increases blood flow to the skin, the major heat-dissipating organ of the body, allowing heat to be transferred from the body to one’s immediate environment via radiation and evaporation.

When one or more of these temperature regulation mechanisms falter, heat gain exceeds heat loss, and body temperature rises.

At very high temperatures, cells throughout the body begin to break down. Cellular proteins become denatured, cell membranes fail, and organs stop working. 

Q:  Who is at greater risk for heat-related illness?

The very young, the elderly, and people with chronic medical conditions are at greatest risk of heat-related illness.

Infants and young children are at risk because of inefficient sweating, an increased metabolism that generates heat even at rest, and a limited ability to control one’s environment. Elderly are at risk because the loss of fluids through sweat and redistribution of blood away from central organs to the skin places a tremendous burden on the heart.

Certain medications can also impair one’s ability to sweat. People who live in mild or cool climates whose bodies have not acclimatized to heat are especially at risk when exposed to a sudden change in temperature such as from a regional heat wave or air travel to a hot climate.

Lastly, young athletes who engage in strenuous outdoor activities for an extended period of time in hot weather are susceptible to a specific type of heat illness called exertional heat stroke.

Whereas classic heat stroke occurs because the body’s physical ability to dissipate heat is compromised, exertional heat stroke occurs because the athlete generates heat at a greater rate than the body is able to remove.

Exertional heat stroke is the third most common cause of death among high school students.

Q:  What are the warning signs of a heat stroke?

Typical symptoms of heat-related illness are muscle cramps, abdominal cramps, nausea, vomiting, diarrhea, headache, dizziness, shortness of breath and weakness.

However, when a person begins to show signs of neurologic involvement such as irritability, irrational behavior, confusion, hallucinations or difficulty being aroused, heat stroke should strongly be considered and immediate medical attention should be sought.

About the author

Susan Hall
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Susan joined Baylor many years ago when Baylor University Medical Center at Dallas was the only Baylor facility in the area. When not at work, she’s outside – Big Bend National Park is her favorite with Glacier National Park a close second.

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The Dangers of Extreme Heat