Definition

Hyperthermia is a condition where the body temperature becomes excessively high, or overheated. It is the opposite of hypothermia, where the body becomes too cold. The normal human body temperature is around 37°C. A body temperature above 37.7°C is considered elevated.

Hyperthermia is not the same as fever. In hyperthermia, the body’s temperature rises beyond a certain threshold that is regulated by the hypothalamus (the part of the brain controlling various bodily functions). In contrast, during a fever, the hypothalamus intentionally raises the body's temperature threshold to help fight off illness or infection.

There is also a condition known as malignant hyperthermia. This is a genetic disorder where a person is susceptible to hyperthermia if they receive specific combinations of certain medications. In such cases, the person's body temperature can rise significantly during or after medication administration.

Read more about hypothermia, here: Hypothermia—Definition, Cause, Symptoms And Treatment

Causes

Hyperthermia occurs when the body absorbs or generates more heat than it can dissipate. Sweating is the body's natural cooling mechanism, but sometimes sweating is insufficient to maintain a normal body temperature. When this happens, the body’s temperature may rise.

Physical activity in extremely hot and humid weather is the most common cause of hyperthermia.

There are several different types of hyperthermia, including:

• Heat cramps: Muscle cramps occur when the body loses electrolytes (salts and other essential substances in body fluids) through sweat. Heat cramps often affect the arms, hands, calves, and feet.
• Heat exhaustion: This is more serious than heat cramps, with body temperatures reaching up to 40°C. Heat exhaustion can progress to heatstroke.
• Heat rash: Prolonged sweating in hot and humid weather can cause skin irritation known as heat rash. It appears as small red pimples or blisters, typically in areas like the elbow creases, under the breasts, near the groin, or on the upper chest and neck.
• Heat stress: This can affect people who work in hot environments, such as firefighters, miners, and construction workers. Heat stress may lead to heat exhaustion or heatstroke.
• Heatstroke: The most severe type of hyperthermia, heatstroke is a life-threatening condition where the body temperature exceeds 40°C. Heatstroke is especially dangerous when body temperature reaches over 41.1°C.

Risk Factor

Everyone can develop hyperthermia, but you are at higher risk if you:

• Are dehydrated
• Are over 65 years old or younger than 4 years old
• Engage in strenuous physical activity in hot weather
• Consume excessive alcohol
• Have an electrolyte imbalance
• Have several medical conditions such as heart, lung, kidney, liver, thyroid, or vascular disorders, or are overweight or underweight
• Take certain medications, such as diuretics, stimulants, sedatives, tranquilizers, heart medication, or blood pressure drugs
• Wear thick clothing in hot weather

Symptoms

Heat cramps typically cause sudden muscle cramps in the legs, calves, thighs, hands, or arms. These cramps can be painful or intense, with muscle soreness after the cramps subside.

Symptoms of heat exhaustion include:

• Blurred vision
• Dizziness
• Fatigue or weakness
• Low blood pressure (hypotension)
• Rapid breathing or heart rate
• Headache
• Muscle pain or cramps
• Lightheadedness or fainting
• Nausea and vomiting

If you want to know more about hypotension, you can read it here: Hypotension—Definition, Cause, Symptoms And Treatment

Heatstroke symptoms often resemble those of heat exhaustion but may also include:

• Dry, non-sweating skin
• Loss of balance
• Confusion or disorientation
• Hot, red, or extremely pale skin
• Low or high blood pressure
• Seizures

Diagnosis

Doctors diagnose hyperthermia through a combination of medical interviews (anamnesis), physical examinations, and additional tests if necessary.

Medical Interview

During the medical interview, the doctor will ask about your symptoms, previous illnesses, and family medical history.

Physical Examination

This includes measuring blood pressure, respiratory rate, pulse, and body temperature.

Diagnostic Tests

After asking questions and conducting a physical examination, the doctor may suggest additional examinations, that is, laboratory tests. If needed, your doctor may recommend laboratory tests like blood or urine tests.

If you want to know more about urine tests, you can read it here: Complete Urinalysis - Indications, Contraindications, Results and Recommendations

Management

If you experience mild to moderate hyperthermia, you should:

• Stop physical activity and rest in a cool, well-ventilated place
• Remove heavy clothing
• Drink fluids with a little salt to replace lost electrolytes. You can drink isotonic fluids or water mixed with a few teaspoons of salt. Avoid caffeinated drinks.
• Apply cold compresses to your skin
• Keep irritated skin dry by using powders or ointments to alleviate discomfort from rashes
• Gently stretch the cramped muscles

In most cases, this can be treated at home. In some situations, the doctor may recommend intravenous fluids.

However, heatstroke is a medical emergency that requires hospital treatment. While waiting for an ambulance or en route to the hospital, try to cool the person as much as possible by:

• Immersing the person in cool water, if possible
• Spraying them with water and fanning them (this is known as evaporative cooling)
• Applying ice packs to the neck, groin, and armpits
• Avoid giving medications, including aspirin and acetaminophen

Complications

Most people recover fully from hyperthermia after resting in a cool place and replacing lost electrolytes. However, individuals with heatstroke may suffer from shock, coma, organ failure, or even death.

Prevention

Most types of hyperthermia are preventable. To reduce your risk:

• Avoid physical activity in hot and humid conditions
• Drink isotonic fluids or water with a little salt
• Never leave children in hot, enclosed spaces, such as cars
• Stay in cool or well-ventilated areas during heat waves
• Wear light, loose, and light-colored clothing when going out in the heat

If you need to work or exercise in hot conditions, allow your body to gradually acclimate. Begin with light work or exercise for about two weeks before progressing to more intense activities. Gradually increase your body's ability to handle higher temperatures. If possible, schedule activities for the cooler parts of the day, such as the morning.

When to See a Doctor?

Contact a doctor if you experience:

• High fever
• Difficulty walking, breathing, or speaking
• Excessive sweating
• Decreased consciousness
• Confusion or disorientation

If you have symptoms of heatstroke, seek medical help immediately.

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