How Hyperthermia Works

Unlike a fever, hyperthermia occurs when your body can't regulate your body temperature.
Unlike a fever, hyperthermia occurs when your body can't regulate your body temperature.

You've probably heard that the typical body temperature for a human is 98.6 degrees Fahrenheit (37 degrees Celsius). That's actually an average -- body temperatures fluctuate throughout the day and can depend upon a person's age or activity level. But it's a good rule of thumb -- if your temperature drops lower or rises higher than the average you may begin to experience health problems.

A fever is a good example. Fever is usually a defense mechanism -- it's the body's response to protect against infection. Most bacteria that cause infection thrive at the body's typical temperature. Raising the temperature inhibits the infection. A part of your brain called the hypothalamus is in charge of maintaining body temperature. Think of it as controlling your internal thermostat -- if you get an infection, the hypothalamus cranks up the temperature dial a couple of notches to slow the infection down [source: The Merck Manuals].


Another example is hyperthermia. Hyperthermia is an elevated body temperature, but it's not like a fever. With a fever, the hypothalamus has reset the body's internal thermostat. Hyperthermia is a symptom that sets in when the body isn't able to maintain temperature properly -- it literally overheats. Hyperthermia can be serious. If the body's temperature rises too high, your organs can suffer damage.

Generally, hyperthermia isn't a disease. It's a side effect of another problem, just like itching is a side effect of an allergic reaction to poison ivy. There is a condition called malignant hyperthermia that's an inheritable disease, but it's not the same thing as the symptom hyperthermia.

Hyperthermia isn't always bad, either. Doctors are experimenting with inducing hyperthermia as part of an overall approach to treating cancer. But elevating the body's temperature under medical supervision and experiencing hyperthermia on your own are two different situations. Hyperthermia can be a warning sign that you're about to be in some serious trouble.

Let's look at what causes hyperthermia.


Hyperthermia Causes

Strenuous activity in warm, humid air can overwhelm your body and lead to heat exhaustion.
Strenuous activity in warm, humid air can overwhelm your body and lead to heat exhaustion.

As we mentioned earlier, hyperthermia is what happens when your body is unable to control your internal temperature. Generally, this happens when you're overwhelmed with heat. One of the ways our bodies deal with excess heat is to generate sweat. The sweat absorbs heat from the skin and evaporates, pulling heat away from us. It's like a natural heat sink.

If you're dehydrated or in an environment that's too warm for your body to handle, you could suffer hyperthermia. Your body's temperature rises -- not because the hypothalamus is adjusting the internal thermostat, but because you're overwhelmed. It's one of the many symptoms of heat exhaustion and heat stroke.


If you're suffering from heat exhaustion, you may feel weak and dizzy. Your body will produce lots of sweat in an attempt to cool you down, which can lead to dehydration. You'll also lose a lot of salt as you sweat. Muscle cramps, dizziness, nausea, vomiting and headaches are other common symptoms. Unchecked, heat exhaustion can lead to heat stroke.

Heat stroke is a serious, potentially deadly condition. Symptoms include dizziness, disorientation, heat cramps and heat rash. With heat stroke, your body stops producing sweat. Your skin will feel hot to the touch and will be either moist or dry. Nausea is another common symptom of heat stroke. Heat stroke victims may also experience seizures.

While hyperthermia is just one symptom of heat exhaustion and heat stroke, it's an early indicator that something is wrong. If you feel uncomfortably warm, you may want to take a break and find a cool spot for a rest.

Other factors that can increase the risk of hyperthermia include circulation problems, lung and heart diseases, and diseased or damaged sweat glands. If you're on medication that affects your ability to sweat, you may also experience hyperthermia more readily.

Some drugs can also cause you to become overheated. It's important to discuss drugs and side effects with your doctor so that you can avoid dangerous conditions that could cause you to suffer hyperthermia.

Next, we'll look at ways to treat hyperthermia.


Hyperthermia Treatments

Since hyperthermia happens because your body can't get rid of excess heat, getting into a cooler area is an important element of treatment. If you're outdoors, you should find a shady spot or, preferably, an air-conditioned area to rest in. Reduce your activity so that you don't generate more heat. Drinking a cool, non-alcoholic and caffeine-free drink is also a good idea. If you've been sweating a lot, you may also want to make sure your beverage has some sodium in it to help replenish your salt levels.

If you're overdressed, you should remove articles of clothing to help you cool down. You can also take a cool shower or bath or use a cold, damp washcloth to help cool your skin. If you're suffering severe hyperthermia and experience elevated blood pressure or heart problems, you should seek medical assistance immediately.


The best way to treat hyperthermia is to avoid it. Try not to spend too much time in hot, humid environments -- humidity will slow down or prevent your sweat from evaporating off your skin and cooling you down. Make sure to drink plenty of liquids -- not just water, which can dilute the electrolytes in your body, but other beverages as well. Fruit juices and sports drinks with sodium in them can help.

Wear light, loose-fitting clothing if you're going to be in a warm environment. Take plenty of rest breaks to avoid building up too high a temperature. Pay attention to how you feel -- if something is wrong, you should be able to tell. Don't ignore the signs. Take time to recover and you'll avoid problems like heat exhaustion or heat stroke.

Believe it or not, overheating isn't always a bad thing. There are situations in which a doctor would recommend a controlled application of hyperthermia. In the next section, we'll look at how doctors use hyperthermia in cancer treatments.


Hyperthermia Cancer Treatments

Not all cases of hyperthermia happen in unplanned and uncontrolled situations. Doctors can induce hyperthermia as part of a treatment approach for some types of cancer. Increasing the temperature of certain tumors renders them more susceptible to the effects of chemotherapy or radiotherapy. It may also make cancer cells more vulnerable to certain types of cancer medication [source: National Cancer Institute].

Some types of cancer cells suffer damage when heated above a particular temperature. Depending on the cancer, this temperature may be low enough to safely use hyperthermia to weaken cancer cells without also damaging healthy tissue. The method of increasing the body's temperature is also important.


One way to induce hyperthermia is to use thermal chambers or hot water blankets. These devices will heat the entire body, raising its temperature. Doctors use these devices to treat metastatic cancers -- these cancers spread from the point of origin to other parts of the body.

Doctors can also target specific regions to induce hyperthermia and treat cancer cells. One technique is perfusion, which involves removing some of the cancer patient's blood, heating the blood and reintroducing it into the body part that contains the cancer. Another approach is continuous hyperthermic peritoneal perfusion (CHPP). Using this method, doctors introduce heated anticancer drugs into the peritoneal cavity -- that's the part of your body that contains your liver, intestines and stomach. They introduce the drugs during surgery.

Doctors can also use microwaves, radiofrequencies or ultrasound to energize cancer cells and induce heat. These methods are very precise -- doctors can concentrate hyperthermia therapy to just the cancer cells and minimize the effects on healthy tissue.

Typically, doctors will pair hyperthermia treatments with some other form of cancer treatment. The doctors will usually apply hyperthermia approaches as a separate treatment -- it's rare to have both chemotherapy or radiation therapy and hyperthermia therapy at the same time.

There are potential side effects. Doctors are introducing heat to a patient's body. There's the potential for burns and blisters. Most side effects are only temporary and not severe [source: National Cancer Institute].


Malignant Hyperthermia

People with malignant hyperthermia have a severe reaction to certain anesthetics.
People with malignant hyperthermia have a severe reaction to certain anesthetics.

While hyperthermia is a symptom indicative of some other problem like heat stroke, malignant hyperthermia is another story. Malignant hyperthermia is an inherited condition. Only one parent has to carry the gene for malignant hyperthermia for a child to inherit it. Doctors can look for signs that someone has malignant hyperthermia by looking for damage in the RYR1 gene [source: U.S. National Library of Medicine].

People with malignant hyperthermia react poorly to some types of anesthesia. A common symptom is a rapid increase in body temperature. Other symptoms can include bleeding, muscle pains or tightness, and the patient's urine turning a dark brown color. People with malignant hyperthermia may also have other muscular diseases.


Malignant hyperthermia is a serious condition and can be life threatening if the patient requires surgery. Often, the first time patients discover they have malignant hyperthermia is when they are given anesthesia. A severe reaction may include an irregular heartbeat.and may cause the patient's kidneys to shut down.

Doctors can use drugs to help regulate the patient's heartbeat and keep the kidneys operating. They can also use special cooling blankets to help manage the patient's body temperature. If the doctors know ahead of time about the condition, they can use anesthetics that don't trigger malignant hyperthermia reactions. The U.S. National Library of Medicine recommends that people with a family history of malignant hyperthermia seek out genetic counseling.

People with malignant hyperthermia can lead normal lives. They can be blood or organ donors. The Malignant Hyperthermia Association of the United States (MHAUS) recommends that adults with malignant hyperthermia wear medical ID tags to let emergency medical technicians know about the condition. A person with malignant hyperthermia has a 50-percent chance to pass it on to his or her child (assuming the other parent doesn't have malignant hyperthermia). Because of that, MHAUS recommends that parents with malignant hyperthermia get a medical ID bracelet for their children.

Medicine has made great progress in identifying and treating people with malignant hyperthermia. According to the Orphanet Journal of Rare Diseases, the mortality rate for patients with malignant hyperthermia dropped from 80 percent to just 5 percent over the last 30 years [source: OJRD].

Learn more about health conditions and how to manage them by following the links on the next page.


Lots More Information

Related Articles

  • American Cancer Soceity. "Hyperthermia." (Sept. 30, 2010)
  • Doerr, Steven. "Hyperthermia and Heat-Related Illnesses." (Sept. 30, 2010)
  • Duke University School of Medicine. "Hyperthermia Treatment." 2007. (Sept. 30, 2010)
  • Heller, Jacob L. and Zieve, David. "Malignant hyperthermia." U.S. National Library of Medicine. July 8, 2009. (Sept. 29, 2010) Kaneshiro, Neil K. and Zieve, David. "Fever." U.S. National Library of Medicine. Jan 29, 2009. (Sept. 29, 2010)
  • Malignant Hyperthermia Association of the United States. "MH Susceptible Patient FAQs." February 2005. (Sept. 29, 2010)
  • Mayo Clinic. "Diuretics." Dec. 17, 2008. (Sept. 30, 2010)
  • National Cancer Institute. "Hyperthermia in Cancer Treatment: Questions and Answers." Aug. 12, 2004. (Sept. 30, 2010)
  • National Cancer Institute. "Metastatic Cancer : Questions and Answers." Sept. 1, 2004. (Sept. 30, 2010)
  • National Institute on Aging. "Hyperthermia: Too Hot for Your Health." Sept. 16, 2010. (Sept. 30, 2010)
  • Rosenberg, Henry, et al. "Malignant hyperthermia." Orphanet Journal of Rare Diseases. April 24, 2007. (Sept. 29, 2010)
  • Tunkel, Allan R. "Defenses Against Infection." The Merck Manuals. October 2008. (Sept. 30, 2010)
  • Vorvick, Linda and Zieve, David. "Body temperature normals." U.S. National Library of Medicine. Feb. 1, 2009. (Sept. 29, 2010)