Heat Stroke: A-to-Z Guide from Diagnosis to Treatment to Prevention

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. If not taken care of quickly, these sun injuries may progress to heat stroke which is a medical emergency. 

What is heat stroke?

Heat stroke happens when our bodies get too hot –when our natural cooling mechanisms are overwhelmed. 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.  We sweat. Sweating is a vital cooling mechanism for our bodies. 

If the surrounding air temperature is hot and humid, if the air is not moving, and if the person is getting dehydrated, heat becomes dangerous as our cooling methods may become overwhelmed, causing the body temperature to quickly rise. 

Who gets heat stroke?

There are two types of heat stroke; classic and exertional.  Those at risk for classic heat stroke include the very young, the elderly, and those on certain classes of medication. Classic heat stroke happens when the environmental temperature is high, and the body isn’t able to keep up with cooling. The smaller the child, the less likely he is to be able to tolerate heat (immature thermoregulatory systems combined with a high body surface area to mass ratio), especially if he is already a bit dehydrated or has a fever, and if there is poor air circulation.

The elderly are also particularly at risk for classic heat stroke, again related to their less effective thermoregulatory systems and chronic conditions.

People who have a prior history of heat injury, who are taking certain 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.

Exertional heat stroke is directly related to physical activity and can affect young healthy athletes or those working in heavy clothing in a hot outdoor environment. It most commonly affects athletes, soldiers, construction workers, and agricultural workers. Exertional heat stroke happens within the first hour of exercise in a hot environment. It is critical to recognize the risks and early warning signs in order to prevent full progression. When caught early enough heat stroke from exertion has a much better prognosis than classic heat stroke with a less than 5% mortality rate. 

What are the symptoms of heat stroke?

Heat stroke is the end of a spectrum of heat-related illnesses. Although symptoms may start mild, they can progress quickly. It is important to recognize and treat even early symptoms of any heat-related illness in order to prevent a medical emergency.  Heat rash, heat edema (swelling of hands and feet), cramping of muscles (especially arms and legs), heat tetany (tingling, especially of wrists), fast breathing,  and an increase heart rate are all signs that a person’s body is having trouble cooling off. 

Heat exhaustion happens right before heat stroke and 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.

Once heat stroke sets in, a person’s condition is very serious. Their temperature rises over 104 degrees, and he or she has an altered mental status.   Immediate treatment is needed. 

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 and recognizing 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. During heat waves, stay in air-conditioned spaces whenever possible. Taking cool showers can be helpful in maintaining a healthy body temperature. Drinking cool liquids frequently is important for hydration.  Check on your elderly neighbors. Children should never be left alone in a car. Take care when spending time outdoors in the hot sun and wear sunscreen, as sunburns can put you more at risk for heat-related illnesses.

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. Coaches and parent volunteers need to offer frequent water breaks to ensure all athletes stay well hydrated. It is also critical to take athletes out of the game or practice if they start showing any signs of heat-related illnesses. Work with coaches and teams to try to time practices to avoid the hottest parts of the day, and this may even mean rescheduling games during extreme heat waves. 

Lightweight clothes that breathe are preferable, and athletes should have time out of helmets at least every 30 minutes.

Heat stroke can be devastating, but it can also be prevented by early recognition and prompt treatment. 

Resources and References

Epstein, Y, et al. Heatstroke. The New England Journal of Medicine 2019; 380(25):2449–2459.