Heat Exhaustion

The body's core temperature is controlled by the hypothalamus, the region of the brain that also controls thirst, hunger, and sexual function. Under normal conditions, the body dissipates excess heat, primarily through the skin and to a lesser extent through the lungs. With heat exhaustion, body systems that regulate temperature become overwhelmed and the body produces more heat than it can dissipate. Approximately 380 deaths result from extreme temperatures each year in the United States, with half of these deaths among people age 65 or older.

Signs and Symptoms

Heat exhaustion is accompanied by the following signs and symptoms:

• Fatigue and malaise
• Headache
• Fever (not exceeding 104°F)
• Dehydration
• Rapid heartbeat
• Dizziness, fainting
• Nausea, vomiting
• Muscle cramps
• Heavy sweating or no sweating at all

When body temperature exceeds 104°F, or if coma or seizure occurs, this indicates that heat exhaustion has progressed to a condition called heat stroke. Heat stroke is a much more serious condition, placing the individual at imminent risk of cardiovascular collapse and death if not promptly reversed.

What Causes It?

Heat exhaustion results most frequently from exposure to high temperature, accompanied by dehydration, usually from not drinking enough fluids. It also can happen when large volumes of sweat are replaced with fluids that contain too little salt.

Who's Most At Risk?

The following factors increase the risk of developing heat exhaustion:

• Dehydration
• Age (the elderly and children under 5 years of age)
• Illness or chronic disability
• Obesity
• Pregnancy
• Cardiovascular disease
• Respiratory disease
• Alcohol consumption
• Physical exertion in hot environments (athletes, military personnel, outdoor laborers are particularly at risk)
• Being unaccustomed to a warm or humid environment
• Medications that interfere with the body's heat-regulation system, including antipsychotics, tranquilizers, antihistamines, tricyclic antidepressants, and some over-the-counter sleeping pills

What to Expect at Your Provider's Office

If you are experiencing symptoms associated with heat exhaustion, you should see your healthcare provider immediately. He or she will perform a physical examination; check your blood pressure, pulse, and temperature; and assess your level of dehydration. Lab tests of blood and urine samples may be needed.

Treatment Options

Prevention

Thirst is not a reliable indicator of impending dehydration; individuals working and exercising in the heat, therefore, should drink plenty of fluids before, during, and after the activity as well as adhere to the following precautions to prevent heat exhaustion:

• Stay in cool or air-conditioned environments when possible on hot days.
• Increase fluid intake; drinking adequate fluids during exercise, for example, prevents heat exhaustion and its complications including muscle damage and kidney failure; dehydration can stress the heart and impair the kidneys' ability to maintain the correct level of fluids and balance of electrolyte (electrolytes are charged elements—like potassium, sodium, phosporous and chloride—essential for the normal function of every cell in the body); drinking fluids during exercise helps to improve heart function, maintain kidney function, and lower the body's core temperature.
• Check on those vulnerable to heat exhaustion (the elderly, for example).
• Avoid alcohol, caffeine and sugar which may all be dehydrating; drink sports drinks that are sweetened with natural juices.
• Exercise or work outdoors during cooler times of day.
• Take cool baths.
• Wear loose, lightweight clothing.
• Athletes should consume 500 ml of fluids before an event and 200 to 300 ml at regular intervals.
• According to the Centers for Disease Control and Prevention, long term prevention of heat exhaustion includes regular, physician approved exercise; novice athletes who are not well conditioned and suddenly participate in prolonged, strenuous activities on a hot day may be at increased risk for heat exhaustion and sudden kidney failure; those who participate in regular exercise over time, allowing their bodies to adjust to hot conditions, may better tolerate exercise on hot days.

Treatment Plan

The primary strategies for treating heat exhaustion are to rest in a cool environment and to take in fluids. Water is adequate under most circumstances. Healthcare 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
Most conventional healthcare providers recommend electrolytes in fluid replacement products for people at risk of heat exhaustion (see Prevention section for more details). Others also suggest that endurance athletes 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
Although studies have not been conducted to look at the application for 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 dissipate heat
• Elder flower (Sambucus nigra) – used to treat fever in Germany and Great Britain; used in combination with peppermint leaf (Mentha x piperita) in the United States and Canada to treat fever
• Subprostrata (Euchresta formosana) – used in traditional Chinese medicine to reduce temperature by dilating blood vessels
• Willow bark (Salix spp.) — used to treat fever in Europe as well as by native Americans and eskimos
• Yarrow (Achillea millefolium) – used to treat fever in Great Britain and other parts of Europe as well as traditional cultures in North America; also used as an Ayurvedic medicine

Also of note:

• Cayenne pepper (Capsicum spp.) contains the ingredient known as capsaicin that may lower body temperature by stimulating sweat glands; many cultures, particularly those in hot climates, incorporate red pepper into their cuisine.

Homeopathy
As with herbs, the use of homeopathic remedies has yet to be scientifically investigated in the treatment of heat exhaustion. However, some common remedies for overheating include:

• Belladonna (Deadly nightshade) – 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 (Nitroglycerin) – 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.

An experienced homeopath would consider your individual case and may recommend treatments to address both the underlying condition and any current symptoms.

Prognosis/Possible Complications

Prognosis is good (24- to 48-hour recovery) if heat stroke is avoided. During rehydration, clinicians will often check fluid and electrolyte levels to avoid complications. Depending on the severity of heat exhaustion, this may require hospitalization. Following Up Your healthcare provider will want to check the fluid levels in your body to see if electrolyte replacement should be continued.

References

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

Baclofen. NMIHI. Accessed at http://www.nmihi.com/b/baclofen.html on July 20, 2018.

Atorvastatin. NMIHI. Accessed at http://www.nmihi.com/a/atorvastatin.html on July 26, 2018.

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.

Clopidogrel. NMIHI. Accessed at http://www.nmihi.com/c/clopidogrel.html on July 20, 2018.

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.

Heat Illness. MedlinePlus. Accessed at https://medlineplus.gov/ on July 20, 2018.

Heat Exhaustion and Heatstroke. American Academy of Family Physicians Accessed at https://familydoctor.org/ on July 20, 2018.

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.

What is heat exhaustion? MedicalNews. Accessed at https://www.medicalnewstoday.com/ on July 20, 2018.