Kids (and pets) left alone in cars have died from heat stroke on days as cool as 70 degrees Fahrenheit. How can this be? We all know that on hot August afternoons the inside of cars can become unbearably hot. But researchers at Stanford University School of Medicine have shown that parked cars can heat just as quickly on mild days – even if the windows are cracked open.

Their study, published in the July 2005 Pediatrics, documented that on sunny days, even if the temperature is a relatively cool 72 degrees, the inside temperature of the car will reach 117 degrees within 60 minutes of turning the car off (and will top 108 degrees within 30 minutes!). Leaving the windows open 1.5 inches made no difference in the final temperature or the rate of rise. Cooling the car with an air conditioner before parking made no difference in the final temperature, but did delay the peak by 8 minutes. On hot days, the rate of rise is the same, but dangerous temperatures can be reached within 5 minutes of closing the car doors, even if the windows are cracked. Overall, when the outside temperature was anywhere between 72 and 96 degrees, the inside temperature rose by an average of 32 degrees in the first 30 minutes.

The results of this can be devastating. First comes heat stress, the discomfort and strain from being left in the hot car. Next, heat exhaustion, where the children or pets can’t get rid of their extra heat and their body temperatures begins to rise. Heat exhaustion often includes intense thirst, anxiety, weakness, headache, nausea, dizziness, and fainting.

Finally, there is heat stroke when the body temperature tops 104 degrees, with no way to get rid of the excess heat (unlike fevers of 104 degrees). For half of those with heat stroke, it results in delirium, convulsions, coma, and death. Even with heat warnings, children die from heat stroke in parked cars every year. It can happen even if the temperature on the other side of the car window is a balmy 72 degrees. Laws regarding leaving young children unattended in cars exist in 9 of the United States. Regardless of the law where you live, preventing heat stroke is straightforward: don’t leave young children or pets unattended in the car. Even for a few minutes.

It’s summer in the Northern Hemisphere – and hot, really hot, in many areas.  We are warm-blooded. Our bodies produce heat. When a muscle contracts, only about 25 percent of the energy is used for the muscle work. A surprising 75 percent of the energy is turned into heat to keep our temperature up. If we didn’t have a way to get rid of extra body heat, our temperatures would keep on climbing.

Strenuous exercise would raise the body temperature by about 2 degrees every five minutes, reaching fatal levels in only about 20 minutes. We get rid of extra heat by radiating it to the cooler surrounding environment, by evaporating extra fluid, and by letting air currents carry it away through convection. If the surrounding air temperature is hot, if the air is not moving, and if the person is getting dehydrated, heat becomes dangerous.

Whether it’s a baby at the beach on a hot day, a toddler left in a sweltering car, or a budding young athlete at an exhausting practice in the sun, heat injuries are more common than people think and prevention is easier than treatment.

Related concepts:

Heat cramps, heat exhaustion, heat prostration

Introduction to heat stroke:

Whether it’s a baby at the beach on a hot day, a toddler left in a sweltering car, or a budding young athlete at an exhausting practice in the sun, heat injuries are more common than people think.

What is heat stroke?

We are warm-blooded. Our bodies produce heat. When a muscle contracts, only about 25 percent of the energy is used for the muscle work. A surprising 75 percent of the energy is turned into heat to keep our temperature up.
If we didn’t have a way to get rid of extra body heat, our temperatures would keep on climbing. Strenuous exercise would raise the body temperature by about 2 degrees every five minutes, reaching fatal levels in only about 20 minutes.
We get rid of extra heat by radiating it to the cooler surrounding environment, by evaporating extra fluid, and by letting air currents carry it away through convection.
If the surrounding air temperature is hot, if the air is not moving, and if the person is getting dehydrated, heat becomes dangerous.

Who gets heat stroke?

The smaller the child, the less likely he is to be able to tolerate heat, especially if he is already a bit dehydrated or has a fever, and if there is poor air circulation.
Heat injuries can occur at any age. Sports and physical activity are generally beneficial and healthy for adolescents; nevertheless, heat injuries are among the leading causes of sports deaths.
People who have a prior history of heat injury, who are taking medicines or drugs (including antihistamines, Ritalin, thyroid hormone, some colic medicines, bed-wetting medicines, diuretics, or laxatives), or who have underlying illnesses (such as diabetes, cystic fibrosis, vomiting, diarrhea, bronchiolitis, or a variety of skin disorders) are at higher risk.

What are the symptoms of heat stroke?

Children’s skin can be quite sensitive to heat. Nursing mom’s often discover this, especially in the summertime, when their baby’s face turns red where it is against the mother’s skin. This redness comes from blood vessels in the area dilating to cool the skin down. Cooling the skin usually makes the rash disappear within hours, or even sooner. Prickly heat (miliaria rubra) is a type of heat rash that lasts.
Heat cramps are common with physical exertion. They usually affect the calf or hamstring muscles.
Heat syncope is fainting due to heat/dehydration.
Heat edema is swelling of the hands or feet from heat. People sometimes get this condition when initially exposed to hot weather.
Heat tetany is tingling, especially of the wrists. Hyperventilation in hot weather can cause heat tetany.
Heat exhaustion usually entails a body temperature of 101 to 104, headache, nausea, vomiting, dizziness, and fainting. It is important to recognize and treat heat exhaustion immediately.
Heat stroke is very serious. A person’s temperature rises over 104 degrees and he or she has an altered mental status. 50 percent of those with heat stroke die from it. There are two types of heat stroke: exertional, with profuse sweating; and classic, in which the skin is hot and dry. Classic heat stroke builds up over days and is most common in infants and in the elderly. It is a true emergency.

Is heat stroke contagious?

Although the desire to appear “tough” on a sports team can be contagious, heat injuries themselves are not contagious.

How long does heat stroke last?

Heat injuries generally last until the body temperature and fluids have been corrected, and any complications treated.

How is heat stroke diagnosed?

The diagnosis is suspected by paying close attention to temperature, airflow, exertion, and hydration. Watching for early symptoms is the key to prompt diagnosis.

How is heat stroke treated?

Heat cramps usually respond to gentle stretching and to re-hydration, especially with an electrolyte solution.
Heat syncope usually responds to cooling (a sponge bath), lying down, and drinking fluids.
Heat edema often goes away on its own, as the person adjusts to the heat.
Heat exhaustion is an emergency. Treatment includes cooling, fans, drinking liquids, and applying ice over the groin and armpits. People typically respond well but prompt treatment is necessary in order to prevent the condition from progressing to heat stroke where treatment may no longer be effective.
Heat stroke is very serious. Call 911. Initial attention should be paid to basic CPR (airway, breathing, and circulation). Aggressive cooling is important, with cooling fans and ice. The patient needs liquids as soon as possible, preferably IV fluids.

How can heat stroke be prevented?

Heat injuries can be prevented. Ensuring good hydration and air circulation are vital. Children should never be left alone in a car. Take care when spending time outdoors in the hot sun.
Children should drink before exercise or sports, and every 20 minutes throughout. Cool liquids are better than warm. Water is fine for exercise up to an hour, but electrolyte solutions are better for exercise that is more strenuous. Keep in mind that most children will not drink this frequently on their own while playing or exercising – they need frequent reminders to ensure that they stay well hydrated.
Lightweight clothes that breathe are preferable, and athletes should have time out of helmets at least every 30 minutes.

Related A-to-Z Information:

Dehydration, Diarrhea, Headache, Miliaria, Vomiting

I’ve been in earthquakes, firestorms, and hurricanes. I’ve been in a storm cellar when a tornado passed outside. All of these natural disasters are powerful dramas, taking and changing lives where they appear. But in the United States, heat waves kill more people each year than all other natural disasters combined!

A wonderful article in the August 13, 2002 New York Times chronicles the statistics. In a heat wave, the temperature is higher than normal for that area. Whether it’s a baby at the beach on a hot day, a toddler left in a sweltering car, or a budding young athlete at an exhausting practice in the sun, heat injuries are real problems for children. Usually, the smaller the child, the less likely he is to be able to tolerate heat, especially if he is already a bit dehydrated or has a fever, and if there is poor air circulation. But heat injuries can occur at any age.

Sports and physical activity are generally beneficial and healthy for adolescents; nevertheless, heat injuries are among the leading causes of sports deaths.

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