hyperthermia

Definition

Hyperthermia is the use of therapeutic heat to treat various cancers on and inside the body.

Purpose

The purpose of hyperthermia is to shrink and hopefully destroy cancer without harming noncancerous cells. It can be used to treat cancer in many areas of the body, including the brain, thyroid, lung, breast, and prostate. It is thought that high temperatures, up to 106 degrees Fahrenheit, can help shrink cancerous tumors. Hyperthermia is starting to be more widely used because it does not have side effects like other forms of cancer treatment such as radiation or chemotherapy. In some instances, hyperthermia is used at the same time with other forms of cancer therapy.

Through years of research, it has been found that the effectiveness of some forms of radiation therapy and chemotherapy are enhanced when combined with hyperthermia.

Although the treatment was considered experimental 15–20 years ago, its proponents believe that the treatment has been accepted by many physicians, and that use of hyperthermia will increase as more cancer centers install the high-tech equipment necessary for regional and whole body hyperthermia. (Currently, cancer care centers offering this treatment are limited.) The American Cancer Society acknowledged that hyperthermia can make the cancer cells of some cancers more responsive to treatment, but still considers the treatment experimental, especially in whole-body form. The National Institutes of Health are sponsoring ongoing clinical trials studying hyperthermia.

Precautions

Patients who have extensive metastasis (spreading of the cancer throughout their body) may not be good candidates for hyperthermia. Patients need to be free of major infections and able to tolerate the high temperatures of the treatment. Caution must be used when areas of the body are heated with external heat sources such as heating pads to avoid potentially dangerous burns.

Description

Hyperthermia can be used on the body from very small areas of the body to the entire body itself. Local hyperthermia refers to heating just one area of body, usually where the tumor is located. Heat can be applied from outside the body using microwaves or high-frequency radio waves. Heat can be applied from inside the body or even inside the tumor itself by the use of thin, heated wires, small tubes filled with hot water, or implanted microwave antennae.

If heat is used to treat an entire organ or limb, it is referred to as regional hyperthermia. High-energy magnets or other devices that produce high energy, and thus heat, are placed over the larger areas to be heated. Another method of regional hyperthermia is the use of perfusion. Hyperthermia perfusion uses the patient's own blood; the blood is removed, heated outside the body, then pumped back into the area that contains the cancer.

For treatment of cancers that have spread throughout the body, whole-body hyperthermia can be considered. Various methods are used to heat up a patient's entire body, including warm-water or electric blankets, hot wax, or thermal chambers which are very much like incubators used to warm newborn babies, except much larger.

Preparation

There are generally no advance preparations needed for a patient considering the use of hyperthermia.

Risks

The major risks of hyperthermia use are pain and external burns. Heat applied directly to the skin can cause minor discomfort to significant pain, especially when high temperatures are used. Blistering and actual burning of the skin can also occur at higher temperatures, although with careful application of the hyperthermia, these side effects are very rare.

Normal Results

The goal of hyperthermia is to control the growth and shrink hyperthermia-sensitive tumors. As stated earlier, hyperthermia can also be used to help sensitize tumors to other cancer treatment modalities such as radiation and chemotherapy.

Abnormal Results

There are generally no abnormal results seen with the use of hyperthermia. Side effects, such as pain and burning from external heat sources, can be minimized with careful application of the heat.

Resources

Books

Abeloff, D. Martin, James O. Armitage, Allen S. Lichter, and John E. Niederhuber. Clinical Oncology. New York: Churchill Livingstone, 2004.

—Edward R. Rosick, D.O., M.P.H.

An abnormally high body core temperature (more than 41°C). See also heat stroke.

An extremely high fever brought on by treatment.

Definition

Hyperthermia involves raising the body's core temperature as a means of eradicating tumors. The treatment simulates fever. Some therapies actually bring on fever through the introduction of fever-causing organisms, while others raise body temperature by directly heating the blood.

Origins

Hyperthermia dates back to investigations begun in 1883 by William B. Coley, M.D., a general surgeon at New York City's Memorial Hospital. Coley was intrigued by a paper published in 1868 by an American family physician named Busch. Busch's paper described a patient with an untreatable sarcoma of the face. Though Busch had been unable to help the patient overcome her cancer, the patient went into remission spontaneously after suffering a bout of the skin infection known as erysipelas. The erysipelas resulted in a high fever ranging from 104°F to 105.8°F (40°C to 41°C). Over the next 20 years, Coley performed a series of experiments to study the effects of elevated temperature on various forms of cancer. After experimenting on animals, Coley moved to treating human cancer patients, injecting them with bacteria to induce high fevers. The bacteria he used are known as Coley's toxins. He reported much success with his method, especially against soft-tissue sarcomas and sarcomas of the bone. Yet his treatment also had serious side effects due to the infections he was introducing.

In spite of its drawbacks, Coley's work intrigued a few other researchers. A study published in Cancer Re-search in 1957 showed that in a review of 450 cases of supposed spontaneous remissions of cancer, 150 of the patients had suffered acute infections that raised their body temperatures. In the 1960s, a Cleveland surgeon and breast cancer specialist, George Crile Jr., published several studies of his experiments in eliminating tumors in mice using heat. Another doctor, Harry Leveen of South Carolina, began building machines that used radio frequencies to heat either the whole body or affected parts. But Leveen's machines were not approved by the Food and Drug Administration (FDA) and Leveen took his inventory to the University of Bangor in Wales. Hyperthermia did not receive much attention in the United States after this point, but practitioners in other countries, particularly Germany, Italy, and Mexico, have reported good results with it. An international congress on hyperthermia has been held each year since 1977.

Benefits

Hyperthermia has been shown in several studies to reduce malignant tumors either alone or in combination with chemotherapy. A 1998 study of patients with breast and ovarian cancer found that hyperthermia therapy increased the effectiveness of chemotherapy. This study suggested that patients undergoing hyperthermia might be successfully treated with lower doses of chemotherapy. A 2003 study demonstrated that women with breast cancer were less likely to experience spread of the cancer to distant lymph nodes or the lungs if they received a combination of whole-body hyperthermia and chemotherapy. A form of localized hyperthermia used to treat benign enlarged prostate glands can be performed in a doctor's office in as little as an hour, and this method does not have the side effects, such as impotence and incontinence, that often accompany traditional prostate surgery.

Newer methods of hyperthermia involving noninvasive (no penetration of skin) microwave technology have been introduced in other countries and were making their way to the United States in early 2002. This technology offered excellent results for some cancer patients in improving five-year survival rates for some aggressive forms of cancer when combined with other cancer therapy procedures.

Description

Hyperthermia therapy involves raising the body's internal temperature, and this can be brought about by several methods. Hyperthermia can involve the whole body, or just an affected local region. For reducing an enlarged prostate, doctors use a device approved by the FDA in 1996 that delivers microwaves to the prostate, while water cools the surrounding tissue to prevent burns. For whole-body hyperthermia, a method used in Europe employs a tent-like device that delivers infrared light to the body. The patient is injected with toxins to provoke a mild fever and then monitored under lights. The lights produce a slow rise in temperature, optimally to 107.6°F (42°C). A prominent practitioner of hyperthermia in Mexico directly heats the patient's blood. Under sedation, the doctor inserts a catheter into each leg near the groin. The two catheter tubes are connected to a heat exchanger. The heat exchanger heats the patient's blood, bringing up the entire body temperature. The patient is monitored by thermometers in the esophagus and rectum. Body temperature is raised to 107.6°F (42°C) for about one hour.

Side Effects

The side effects of hyperthermia depend on how it is delivered. Cardiac problems are possible. The patient should be closely monitored during the procedure and after. For treatment of the prostate, localized hyperthermia seems to be without the side effects of traditional prostate surgery.

Research & General Acceptance

Though research into hyperthermia as a cancer treatment began in the United States, most active practitioners are in Europe or Mexico as of 2004. However, the heat therapy for prostate enlargement was approved in the United States in 1996. Localized hyperthermia was being studied in the late 1990s for treatment of other conditions, including menorrhagia (heavy menstrual periods) and malignant tumors of the liver and rectum. Whole body hyperthermia continues to be studied and tested for its impact on cancers, and a test underway in 1999 in Texas examined this therapy for patients with AIDS. Several studies in 2003 showed hyperthermia's positive effects on cellular immune response in cancer patients, especially when used along with chemotherapy. One study suggested that the effectiveness of certain chemotherapy drugs used for leukemia patients could be enhanced by adding hyperthermia to the treatment.

Training & Certification

Practitioners performing hyperthermia are certified medical doctors and such trained assistants as nurses and anesthesiologists.

Resources

Periodicals

"BSD Medical Licenses Right to NIH Non-invasive Deep Hyperthermia Cancer Therapy." BIOTECH Patent News (February 2002).

"Cancer (therapy)." Women's Health Weekly (August 10, 1998): 17.

"Hyperthermia and Ifosfamide Induced Cytotoxicity is Subadditive." Proteomics Weekly (March 24, 2003):10.

"Hyperthermia Improves Immune Response to Human Hepato-cellular Carcinoma." Vaccine Weekly (July 30, 2003):10.

Jack, David. "Waxing Hot and Cold in the Surgical Arena." The Lancet (April 11, 1998): 1110.

Key, Sandra, and Michelle Marble. "Hyperthermia Treatment Evaluated" Cancer Weekly Plus (February 8, 1999): 14.

Walker, Morton. "Medical Journalist Report of Innovative Biologics: Whole Body Hyperthermia Effect on Cancer." Townsend Letter for Doctors & Patients (June 30, 1998): 60–66.

"Whole-body Hyperthermia and Metronomic Chemotherapy Prevent Cancer Metastasis." Angiogenesis Weekly (April 11, 2003):4.

Wu, Corrina, Shannon Brownlee, and Anna Mulrine. "Zapping a Problem Prostate." U.S. News & World Report (May 20, 1996): 71.

[Article by: Angela Woodward; Teresa G. Odle]

An abnormally high body core temperature (more than 40 °C). Compare hypothermia. See also heat stroke.

1. greatly increased body temperature. May have effect as teratogen.
2. heat therapy. Used in the treatment of tumors, often in conjunction with chemotherapy or radiation. Whole body, regional or localized hyperthermia is induced with electromagnetic radiation, radiofrequency current heating or ultrasonic heating.

• epidemic h. — poisoning by Neotyphodium (Acremonium) coenophialum.
• idiopathic h. — term applied in error to the effects of ergotism under conditions of high ambient temperature. See also rye ergot, Neotyphodium (Acremonium) coenophialum.
• malignant h. — a drug induced stress syndrome of pigs which have been treated with halothane or suxamethonium. Isolated cases have been reported in dogs and cats. The clinical syndrome includes muscle rigidity and hyperthermia. It is fatal and susceptibility to it is inherited. See also porcine stress syndrome.

This article is in need of attention from an expert on the subject. WikiProject Medicine or the Medicine Portal may be able to help recruit one. (September 2009)

Hyperthermia is an elevated body temperature due to failed thermoregulation. Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. When the elevated body temperatures are sufficiently high, hyperthermia is a medical emergency and requires immediate treatment to prevent disability and death.

The most common causes are heat stroke and adverse reactions to drugs. Heat stroke is an acute condition of hyperthermia that is caused by prolonged exposure to excessive heat and/or humidity. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to effectively deal with the heat, causing the body temperature to climb uncontrollably. Hyperthermia is a relatively rare side effect of many drugs, particularly those that affect the central nervous system. Malignant hyperthermia is a rare complication of some types of general anesthesia.

Hyperthermia can be created artificially by drugs or medical devices. Hyperthermia therapy may be used to treat some kinds of cancer and other conditions, most commonly in conjunction with radiotherapy.^[1]

Hyperthermia differs from a fever in the mechanism that causes the elevated body temperatures: a fever is caused by a change in the body's temperature set-point.

The opposite of hyperthermia is hypothermia, which occurs when an organism's temperature drops below that required for normal metabolism. Hypothermia is caused by prolonged exposure to low temperatures and is also a medical emergency requiring immediate treatment.

Contents 1 Signs and symptoms 2 Pathophysiology 3 Causes 3.1 Heat stroke 3.2 Drugs 3.3 Personal Protective Equipment 3.4 Other 4 Diagnosis 5 Prevention & Mitigation 6 Treatment 7 Epidemiology 8 See also 9 References 10 External links

Signs and symptoms

The normal human body temperature in a healthy adult can be as high as 37.7°C (99.9°F) in the late afternoon.^[2] Hyperthermia requires an elevation from the temperature that would otherwise be expected. Such elevations range from mild to extreme; body temperatures above 40°C (104 °F) can be life-threatening.

Hot, dry skin is a typical sign of hyperthermia.^[2] The skin will become red and hot as blood vessels dilate in an attempt to increase heat dissipation, sometimes leading to swollen lips. An inability to cool the body through perspiration causes the skin to feel dry. Fever, by contrast, frequently produces cool, damp skin.

Other signs and symptoms vary depending on the cause. The dehydration associated with heat stroke can produce nausea, vomiting, headaches, and low blood pressure. This can lead to fainting or dizziness, especially if the person stands suddenly.

In the case of severe heat stroke, the person may become confused or hostile, and may seem intoxicated. Heart rate and respiration rate will increase (tachycardia and tachypnea) as blood pressure drops and the heart attempts to supply enough oxygen to the body. The decrease in blood pressure can then cause blood vessels to contract, resulting in a pale or bluish skin color in advanced cases of heat stroke. Some victims, especially young children, may have seizures. Eventually, as body organs begin to fail, unconsciousness and coma will result.

Pathophysiology

A summary of the differences between hyperthermia, hypothermia, and fever.
Hyperthermia: Characterized on the left. Normal body temperature (thermoregulatory set-point) is shown in green, while the hyperthermic temperature is shown in red. As can be seen, hyperthermia can be conceptualized as an increase above the thermoregulatory set-point.
Hypothermia: Characterized in the center: Normal body temperature is shown in green, while the hypothermic temperature is shown in blue. As can be seen, hypothermia can be conceptualized as a decrease below the thermoregulatory set-point.
Fever: Characterized on the right: Normal body temperature is shown in green. It reads "New Normal" because the thermoregulatory set-point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic.

A fever occurs when the body sets the core temperature to a higher temperature, through the action of the pre-optic region of the anterior hypothalamus. For example, in response to a bacterial or viral infection, the body will raise its temperature, much like raising the temperature setting on a thermostat.

In contrast, hyperthermia occurs when the body temperature is raised without the consent of the heat control centers.

Causes

Heat stroke

Heat stroke is due to an environmental exposure to heat, resulting in an abnormally high body temperature.^[2] In severe cases, temperatures can exceed 40 C.^[3] Heat stroke may be exertional or non-exertional, depending on whether the person has been exercising in the heat. Significant physical exertion on a very hot day can generate heat beyond a health body's ability to cool itself, because the heat and humidity of the environment reduces the efficiency of the body's normal cooling mechanisms.^[2] Other factors, such as drinking too little water, can exacerbate the condition. Non-exertional heat stroke is typically precipitated by medications that reduce vasodilation, sweating, and other heat-loss mechanisms, such as anticholingeric drugs, antihistamines, and diuretics.^[2] In this situation, the body's tolerance for the excessive environmental temperatures can be too limited to cope with the heat, even while resting.

Drugs

Some drugs cause excessive internal heat production, even in normal temperature environments.^[2] The rate of drug-induced hyperthermia is higher where use of these drugs is higher.^[2]

• Many psychotropic medications, such as selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), and tricyclic antidepressants, can cause hyperthermia.^[2] Serotonin syndrome often presents following exposure to multiple drugs. Similarly, neuroleptic malignant syndrome is an uncommon reaction to neuroleptic agents.^[4] These syndromes are differentiated by the other associated symptoms, such as tremor in serotonin syndrome and "lead-pipe" muscle rigidity in neuroleptic malignant syndrome.^[2]
• Many illicit drugs, including amphetamines,^[5] cocaine,^[6] PCP, LSD, and MDMA can produce hyperthermia as an adverse effect.^[2]
• Malignant hyperthermia is a rare reaction to common anesthetic agents (such as halothane) or a reaction to the paralytic agent succinylcholine. Malignant hyperthermia is a genetic condition, and can be fatal.^[2]

Personal Protective Equipment

People working in industry, the military and first responders must wear Personal Protective Equipment (PPE) to protect themselves from hazardous threats such as chemical agents, gases, fire, small arms and even Improvised Explosive Devices (IEDs). This PPE can include a range of hazmat suits, firefighting turnout gear, body armor and bomb suits, among many other forms. Depending on its design, PPE often ‘encapsulates’ the wearer from a threat and creates what is known as a microclimate, due to an increase in thermal resistance and decrease in vapor permeability. As a person performs physical work, the body’s natural method of thermoregulation (i.e., sweating) becomes ineffective. This is compounded by increased work rates, high ambient temperatures and humidity levels, and direct exposure to the sun. The net effect is that protection from one or more environmental threats inadvertently brings on the threat of heat stress.

Other

Other possible, but rare, causes of hyperthermia are thyrotoxicosis and the presence of a tumor on the adrenal gland, called a pheochromocytoma, both of which can cause increased heat production.^[2] Damage to the central nervous system, such as from a brain hemorrhage, a severe, uncontrolled epileptic seizure called status epilepticus, and other kinds of damage to the hypothalamus can also cause hyperthermia.^[2]

Diagnosis

Hyperthermia is generally diagnosed in the presence of an unexpectedly high body temperature and a history that suggests hyperthermia instead of a fever.^[2] Most commonly this means that the elevated temperature has appeared in a person that was working in a hot, humid environment (heat stroke) or that was taking a drug for which hyperthermia is a known side effect (drug-induced hyperthermia). The presence of other signs and symptoms related to hyperthermia syndromes, such as the extrapyramidal symptoms that are characteristic of neuroleptic malginant syndrome, and the absence of signs and symptoms more commonly related to infection-related fevers, are also considered in making the diagnosis.

If fever-reducing drugs lower the body temperature, even if the temperature does not return entirely to normal, then hyperthermia is excluded.^[2]

Prevention & Mitigation

In cases where heat stress is caused by physical exertion, hot environments or wearing protective equipment it can be prevented or mitigated by taking frequent rest breaks, staying hydrated and carefully monitoring body temperature. However, in situations demanding prolonged exposure to a hot environment or wearing protective equipment, a personal cooling system is required as a matter of health and safety. A variety of active or passive technologies personal cooling systems exist which can be categorized by their power sources and whether they are man or vehicle-mounted.

Due to the broad variety of operating conditions, a personal cooling system must meet specific requirements, such as the rate and duration of cooling, need for physical mobility and autonomy, access to power, and conformance with health & safety regulations. For example, active liquid systems operate on the basis of chilling water and circulating it through a garment that cools the skin surface area that it covers through conduction. This type of system has proven successful in certain Military, Law Enforcement and Industrial applications. Bomb disposal technicians wearing bomb suits to protect against an Improvised Explosive Device (IED) use a small ice-based chiller unit strapped to their leg with a Liquid Circulating Garment, usually a vest, worn over their torso to maintain their core temperature at safe levels. By contrast, soldiers traveling in combat vehicles can face microclimate temperatures in excesss of 150 degrees Fahrenheit and require a multiple-user vehicle-powered cooling system with rapid connection capabilities. Requirements for Hazmat teams, the medical community and workers in heavy-industry will vary further.

Treatment

Treatment for hyperthermia depends on its cause, as the underlying cause must be corrected. Mild hyperthemia caused by exertion on a hot day might be adequately treated through self-care measures, such as drinking water and resting in a cool place. Hyperthermia that results from drug exposures is frequently treated by cessation of that drug, and occasionally by other drugs to counteract them. Fever-reducing drugs such as paracetamol and aspirin have no value in treating hyperthermia.^[2]

When the body temperature is significantly elevated, mechanical methods of cooling are used to remove heat from the body and to restore the body's ability to regulate its own temperatures.^[2] Passive cooling techniques, such as resting in a cool, shady area and removing clothing can be applied immediately. Active cooling methods, such as sponging the head, neck, and trunk with cool water, remove heat from the body and thereby speed the body's return to normal temperatures. Drinking water and turning a fan or dehumidifying air conditioning unit on the affected person may improve the effectiveness of the body's evaporative cooling mechanisms (sweating).

Sitting in a bathtub of tepid or cool water (immersion method) can remove a significant amount of heat in a relatively short period of time. However, immersion in very cold water is counterproductive, as it causes vasoconstriction in the skin and thereby prevents heat from escaping the body core.

When the body temperature reaches about 40 C, or if the affected person is unconscious or showing signs of confusion, hyperthermia is considered a medical emergency that requires treatment in a proper medical facility. In a hospital, more aggressive cooling measures are available, including intravenous hydration, gastric lavage with iced saline, and even hemodialysis to cool the blood.^[2]

Epidemiology

The frequency of environmental hyperthermia can vary significantly from year to year depending on factors such as heat waves.

See also

• Dehydration
• Heat cramps
• Hypernatremia
• Hyperpyrexia
• Hyponatremia

References

1. ^ Information from the U.S. National Cancer Institute
2. ^ ^{a b c d e f g h i j k l m n o p q r} Fauci, Anthony, et al. (2008). Harrison's Principles of Internal Medicine (17 ed.). McGraw-Hill Professional. pp. 117-121. ISBN 9780071466332. 
3. ^ Tintinalli, Judith (2004). Emergency Medicine: A Comprehensive Study Guide, Sixth edition. McGraw-Hill Professional. p. 1187. ISBN 0071388753. 
4. ^ Tintinalli, Judith (2004). Emergency Medicine: A Comprehensive Study Guide, Sixth edition. McGraw-Hill Professional. p. 1818. ISBN 0071388753. 
5. ^ Marx, John (2006). Rosen's emergency medicine: concepts and clinical practice. Mosby/Elsevier. p. 2894. ISBN 9780323028455. 
6. ^ Marx, John (2006). Rosen's emergency medicine: concepts and clinical practice. Mosby/Elsevier. p. 2388. ISBN 9780323028455. 

v • d • e Consequences of external causes (T66-T88, 990-999) Temperature/radiation elevated: Hyperthermia · Heat syncope · Radiation poisoning reduced: Hypothermia · Immersion foot · Chilblain Air Hypoxia/Asphyxia · Barotrauma (Aerosinusitis, Decompression sickness) · Altitude sickness/Chronic mountain sickness Food Starvation Maltreatment Physical abuse · Sexual abuse · Psychological abuse Emesis Motion sickness · Seasickness · Airsickness · Space adaptation syndrome Other Electric shock · Anaphylaxis · Angioedema Hypersensitivity (Allergy, Arthus reaction) Subcutaneous emphysema Certain early complications of trauma embolism (Air, Fat) Crush syndrome/Rhabdomyolysis Contracture/Volkmann's contracture/Compartment syndrome Complications of surgical and medical care transfusion reactions: Transfusion hemosiderosis · TRALI · TACO · TA-GvHD · FNHTR · Acute/Delayed hemolytic transfusion reaction other: Serum sickness · Malignant hyperthermia · Herxheimer reaction · Graft-versus-host disease · Tumor lysis syndrome

External links

• Recognizing Heath Stroke, Institute for Good Medicine at the Pennsylvania Medical Society
• International Red Cross Information on Heat Stroke
• Hiking and Camping Note Book Heat Stroke Advice
• BBC Heat Illness News and Information
• Environment Canada's Heat Index (humidex) Chart
• Working in Hot Environments, from the United States' National Institute for Occupational Safety and Health (NIOSH)
• Excessive Heat Events Guidebook, from the United States' Environmental Protection Agency (EPA)
• Enhanced Home & Family Heatwave Preparedness
• Cold Water Immersion: The Gold Standard for Exertional Heatstroke Treatment
• Physiological Responses to Exercise in the Heat -- Chapter 3 of Nutritional Needs in Hot Environments by the Institute of Medicine of the U.S. National Academies (of Science) (N.B.: entire book is available in HTML format via this link)
• US Army Natick Soldier Center: In-Theatre Microclimate Cooling
• Microclimate Cooling Systems for Military, First Responders and Industrial Personnel

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