Heat Stroke: Symptoms and Treatment
August 22, 2019
WebMD Medical Reference Reviewed by Carol DerSarkissian
Heatstroke is the most serious form of heat injury and is considered a medical emergency. If you suspect that someone has heat stroke -- also known as sunstroke -- call 911 immediately and give first aid until paramedics arrive.
Heatstroke can kill or cause damage to the brain and other internal organs. Although heat stroke mainly affects people over age 50, it also takes a toll on healthy young athletes.
Heatstroke often occurs as a progression from milder heat-related illnesses such as heat cramps, heat syncope (fainting), and heat exhaustion. But it can strike even if you have no previous signs of heat injury.
Heatstroke results from prolonged exposure to high temperatures -- usually in combination with dehydration -- which leads to failure of the body's temperature control system. The medical definition of heatstroke is a core body temperature greater than 104 degrees Fahrenheit, with complications involving the central nervous system that occur after exposure to high temperatures. Other common symptoms include nausea, seizures, confusion, disorientation, and sometimes loss of consciousness or coma.
The hallmark symptom of heatstroke is a core body temperature above 104 degrees Fahrenheit. But fainting may be the first sign.
Other symptoms may include:
If you suspect that someone has a heat stroke, immediately call 911 or transport the person to a hospital. Any delay seeking medical help can be fatal.
While waiting for the paramedics to arrive, initiate first aid. Move the person to an air-conditioned environment -- or at least a cool, shady area -- and remove any unnecessary clothing.
If possible, take the person's core body temperature and initiate first aid to cool it to 101 to 102 degrees Fahrenheit. (If no thermometers are available, don't hesitate to initiate first aid.)
Try these cooling strategies:
Do not use ice for older patients, young children, patients with chronic illness, or anyone whose heatstroke occurred without vigorous exercise. Doing so can be dangerous.
If emergency response is delayed, call the hospital emergency room for additional instructions.
Heatstroke is most likely to affect older people who live in apartments or homes lacking air conditioning or good airflow. Other high-risk groups include people of any age who don't drink enough water, have chronic diseases, or who drink excessive amounts of alcohol.
Heatstroke is strongly related to the heat index, which is a measurement of how hot you feel when the effects of relative humidity and air temperature are combined. A relative humidity of 60% or more hampers sweat evaporation, which hinders your body's ability to cool itself.
The risk of heat-related illness dramatically increases when the heat index climbs to 90 degrees or more. So it's important -- especially during heat waves -- to pay attention to the reported heat index, and also to remember that exposure to full sunshine can increase the reported heat index by 15 degrees.
If you live in an urban area, you may be especially prone to develop heatstroke during a prolonged heatwave, particularly if there are stagnant atmospheric conditions and poor air quality. In what is known as the "heat island effect," asphalt and concrete store heat during the day and only gradually release it at night, resulting in higher nighttime temperatures.
Other risk factors associated with heat-related illness include:
Age. Infants and children up to age 4, and adults over age 65, are particularly vulnerable because they adjust to heat more slowly than other people.
Health conditions. These include heart, lung, or kidney disease, obesity or underweight, high blood pressure, diabetes, mental illness, sickle cell trait, alcoholism, sunburn, and any conditions that cause fever.
Medications. These include antihistamines, diet pills, diuretics, sedatives, tranquilizers, stimulants, seizure medications (anticonvulsants), heart and blood pressure medications such as beta-blockers and vasoconstrictors, and medications for psychiatric illnesses such as antidepressants and antipsychotics. Illegal drugs such as cocaine and methamphetamine also are associated with increased risk of heat stroke.
People with diabetes -- who are at increased risk of emergency room visits, hospitalization, and death from heat-related illness -- may be especially likely to underestimate their risk during heat waves, according to a recent study presented at the Endocrine Society's annual meeting by researchers from the Mayo Clinic in Arizona, the National Ocean and Atmospheric Administration, and the National Weather Service.
Check with your doctor to see if your health conditions and medications are likely to affect your ability to cope with extreme heat and humidity.
When the heat index is high, it's best to stay in an air-conditioned environment. If you must go outdoors, you can prevent heat stroke by taking these steps:
Other strategies for preventing heat stroke include:
Avoid fluids containing caffeine or alcohol, because both substances can make you lose more fluids and worsen heat-related illness. Also, do not take salt tablets unless your doctor has told you to do so. The easiest and safest way to replace salt and other electrolytes during heat waves is to drink sports beverages or fruit juice.
Check with your doctor before increasing liquid intake if you have epilepsy or heart, kidney, or liver disease; are on fluid-restricted diets, or have a problem with fluid retention.
If you live in an apartment or house without fans or air conditioning, try to spend at least two hours each day -- preferably during the hottest part of the day -- in an air-conditioned environment. At home, draw your curtains, shades, or blinds during the hottest part of the day, and open windows at night on two sides of your building to create cross-ventilation.
If you're a senior who either can't afford to buy or run an air conditioner, check with your local Area Agency on Aging for programs that can assist you. One such program is the Low-Income Home Energy Assistance Program (LIHEAP).
After you've recovered from heat stroke, you'll probably be more sensitive to high temperatures during the following week. So, it's best to avoid hot weather and heavy exercise until your doctor tells you that it's safe to resume your normal activities.