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Heat exhaustion

• Signs and Symptoms
• What Causes It?
• Who's Most At Risk?
• What to Expect at Your Provider's Office
• Treatment Options
• Prognosis/Possible Complications
• Following Up
• Supporting Research

Heat exhaustion occurs when your body gets too hot. The body's core temperature is controlled by the hypothalamus, the part of the brain that also controls thirst and hunger. Normally, the body gets rid of excess heat by sweating. But if you are exposed to high temperatures (working outdoors in the summer, for example) for a long time and don't replace the fluids you lose, the body systems that regulate temperature become overwhelmed. As a result, your body produces more heat than it can dissipate. Heat exhaustion requires immediate attention, because it can progress to heat stroke, a serious (even fatal) illness.

Signs and Symptoms

Heat exhaustion is accompanied by the following signs and symptoms:

• Heavy sweating
• Fatigue
• Headache
• Pale, clammy skin
• Thirst
• Rapid heartbeat
• Dizziness, fainting
• Nausea, vomiting
• Muscle cramps

If body temperature goes above 104°F, or if coma or seizure occurs, the patient likely has a more serious condition called heat stroke. Heat stroke can quickly lead to heart attack and death if not treated.

What Causes It?

Heat exhaustion occurs most often when you are exposed to high temperatures and become dehydrated, usually from not drinking enough fluids. It also can happen when large volumes of sweat are replaced with fluids that don't contain enough salt.

Who's Most At Risk?

The following factors increase the risk of developing heat exhaustion:

• Being dehydrated
• Age (the elderly and children under 5 years of age)
• Illness or chronic disability
• Obesity
• Pregnancy
• Cardiovascular disease
• Respiratory disease
• Drinking alcohol
• Physical exertion in hot or humid environments (athletes, military personnel, outdoor laborers are particularly at risk)
• Taking medications that interfere with the body's ability to cool itself, including antipsychotics, tranquilizers, antihistamines, tricyclic antidepressants, and some over-the-counter sleeping pills

What to Expect at Your Provider's Office

If you have symptoms of heat exhaustion, you should see a doctor immediately. The doctor will perform a physical examination; check your blood pressure, pulse, and temperature; and assess how dehydrated you are. Lab tests of blood and urine samples may be needed.

Treatment Options

Prevention

If you are working or exercising in the heat, don't wait until you get thirsty to drink fluids. Instead, drink plenty of fluids before, during, and after the activity. Take the following precautions to prevent heat exhaustion:

• Stay in cool or air-conditioned spaces when possible on hot days.
• Drink more fluids than usual. Drinking enough fluids during exercise, for example, helps to improve heart function, maintain kidney function, and lower the body's core temperature. Dehydration can stress the heart and reduce the kidneys' ability to maintain the correct balance of electrolytes (charged elements -- such as potassium, sodium, phosphorous and chloride -- essential for the normal function of every cell in the body).
• Check on those vulnerable to heat exhaustion (the elderly, for example).
• Avoid alcohol, caffeine, and sugar, which can cause dehydration. Drink water or sports drinks sweetened with natural juices.
• Exercise or work outdoors during cooler times of day.
• Take cool baths.
• Wear loose, lightweight clothing.
• Long-term prevention of heat exhaustion includes regular, doctor-approved exercise. Those who exercise regularly over time, allowing their bodies to adjust to hot conditions, may better tolerate exercise on hot days.

Treatment Plan

The primary treatment for heat exhaustion is to rest in a cool environment (a shady spot or, better, an air-conditioned room) and to drink cool (not icy) fluids. Water is usually enough to reverse dehydration, or you can drink a sports drink that contains electrolytes. You can also cool down by spraying yourself with water and fanning.

Health care providers may recommend saline electrolyte solutions, administered orally for mild dehydration and intravenously in more severe cases.

Drug Therapies

Oral or intravenous saline electrolyte solution may be used.

Complementary and Alternative Therapies

Nutrition and Supplements

Health care providers may recommend drinking fluids that contain electrolytes (see Prevention section for more details). Endurance athletes may want to take mineral supplements including:

• Calcium
• Magnesium
• Potassium

Foods high in these nutrients include dark leafy greens, nuts, seeds, whole grains, sea vegetables, blackstrap molasses, and bananas.

Herbs

The most important treatment for heat exhaustion is replacing lost fluids by drinking water or a sports drink. Some herbs may help reduce body temperature, but if you have symptoms of heat exhaustion you should talk to your health care provider before taking anything. Although no studies have examined using herbs to treat heat exhaustion specifically, herbs traditionally used to reduce fever or lower body temperature include:

• Chinese skullcap ( Scutellaria baicalensis ) -- used in traditional Chinese medicine to reduce temperature by dilating blood vessels near the surface of the skin, which helps the body get rid of heat
• Elder flower ( Sambucus nigra) -- used to treat fever, sometimes combined with peppermint leaf ( Mentha x piperita )
• Willow bark ( Salix spp. ) -- used to treat fever. Do not take willow bark if you are allergic to aspirin, and do not give it to children under 16 because of risk of developing Reyes syndrome, a serious illness.
• Yarrow (Achillea millefolium ) -- used to treat fever
• Cayenne pepper (Capsicum spp. ) -- contains capsaicin, which may lower body temperature by stimulating sweat glands

Homeopathy

Although very few studies have examined the effectiveness of specific homeopathic therapies, professional homeopaths may consider the following remedies for the treatment of fevers based on their knowledge and experience. Before prescribing a remedy, homeopaths take into account a person's constitutional type -- your physical, emotional, and psychological makeup. An experienced homeopath assesses all of these factors when determining the most appropriate treatment for each individual.

• Belladonna -- often used for fever, particularly if flushed with bright red skin and dulled mentation. The person for whom this treatment is appropriate does not usually feel thirsty even though his or her mouth and skin are dry
• Glonoinum -- used for fever if the person is flushed and sweaty. The person for whom this is appropriate may complain of a hot face but cold extremities, as well as irritability, headache, and confusion. It is often used for ailments brought on by overexposure to the sun.

Prognosis/Possible Complications

If you avoid heat stroke, recovering from heat exhaustion usually takes 24 - 48 hours. Depending on the severity of heat exhaustion, you may be hospitalized so your fluid and electrolyte levels can be monitored to avoid complications.

Following Up

Your health care provider will want to check the fluid levels in your body to see if electrolyte replacement should be continued.

Supporting Research

Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs . Newton, Mass: Integrative Medicine Communications; 2000:103-105; 419-423.

Cecil RI, Plum F, Bennett JC, eds. Cecil Textbook of Medicine . 20th ed. Philadelphia, Pa: W.B. Saunders; 1996.

Centers for Disease Control and Prevention. Heat-related illnesses and deaths -- Missouri, 1998, and United States, 1997–1996. JAMA . 1999;282(3):227-228.

Dambro MR, ed. Griffith's 5 Minute Clinical Consult . Baltimore, Md: Lippincott Williams & Wilkins; 1999.

Dib B. Effects of intrathecal capsaicin on autonomic and behavioral heat loss responses in the rat. Pharmacol Biochem Behav. 1987;28(1):65-70.

Duthie EH, Katz PR, Kersey R, eds. Practice of Geriatrics . 3rd ed. Philadelphia, Pa: W.B. Saunders; 1998.

Eichner ER. Treatment of suspected heat illness. Int J Sports Med . 1998;19(suppl 2):S150-S153.

Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine . 14th ed. New York, NY: McGraw-Hill Book Co; 1998.

Fishbane S. Exercise-induced renal and electrolyte changes. Phys Sportsmedicine . 1995;23(8):39-40, 42-46.

Furman JA, Assell C. Acute, exercise-induced compartment syndrome, rhabdomyolysis, and renal failure—a case report . Nutr Clin Pract. 1999;14(6):296-298.

Glazer JL. Management of heatstroke and heat exhaustion. Am Fam Physician . 2005 Jun 1;71(11):2133-40.

Lin MT, Ho ML, Chandra A, Hsu HK. Serotoninergic mechanisms of the hypothermia induced by Clerodenron fragrans (Ventenaceae) in the rat . Am J Chin Med. 1981;9(2):144-154.

McCormick CC, Garlich JD. The interaction of phosphorus nutrition and fasting on the survival time of young chickens acutely exposed to high temperature. Poult Sci. 1982;61(2):331-336.

Rakel RE, ed. Conn's Current Therapy . 51st ed. Philadelphia, Pa: W.B. Saunders Co; 1999.

Rosen P, Barkin R, eds. Emergency Medicine: Concepts and Clinical Management . 4th ed. St. Louis, Mo: Mosby-Year Book; 1998.

Semenza JC, McCullough JE, Flanders WD, McGeehin MA, Lumpkin JR. Excess hospital admissions during the July 1995 heat wave in Chicago. Am J Prev Med . 1999;16(4):269-277.

Simon HB. Hyperthermia. N Engl J Med . 1993;329(7):483-487.

Von Duvillard SP, Braun WA, Markofski M, Beneke R, Leithauser R. Fluids and hydration in prolonged endurance performance. Nutrition . 2004 Jul-Aug;20(7-8):651-6.

• Review Date: 12/10/2006
• Reviewed By: Steven D. Ehrlich, N.M.D., private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.

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