heat exhaustion

Also found in: Dictionary, Thesaurus, Financial, Encyclopedia, Wikipedia.
Related to heat exhaustion: salt depletion, dehydration, heat cramps


1. a state of extreme mental or physical fatigue.
2. the state of being drained, emptied, consumed, or used up.
heat exhaustion see heat exhaustion.


1. energy that raises the temperature of a body or substance.
2. estrus.
3. a rise in temperature.
4. to cause to increase in temperature.

Heat is associated with molecular motion, and is generated in various ways, including combustion, friction, chemical action, and radiation. The total absence of heat is absolute zero, at which all molecular activity ceases.
Body Heat. Heat Production. Body heat is the byproduct of the metabolic processes of the body. The hormones thyroxine and epinephrine increase metabolism and consequently increase body heat. Muscular activity also produces body heat. At complete rest (basal metabolism) the amount of heat produced from muscular activity may be as low as 25 per cent of the total body heat. During exercise or shivering the percentage may rise to 60 per cent. Body temperature is regulated by the thermostatic center in the hypothalamus. A body temperature above the normal range is called fever.
Heat Loss. Loss of body heat occurs in three ways: by radiation (heat waves), by conduction to air or objects in contact with the body, and by evaporation of perspiration. Some body heat is lost in exhalation of air and in elimination of urine and feces.
Applications of External Heat. Purposes. Local applications of heat may be used to provide warmth and promote comfort, rest, and relaxation. Heat is also applied locally to promote suppuration and drainage from an infected area by hastening the inflammatory process; to relieve congestion and swelling by dilating the blood vessels, thereby increasing circulation; and to improve repair of diseased or injured tissues by increasing local metabolism.
Effects. Factors that determine the physiologic action of heat include the type of heat used, length of time it is applied, age and general condition of the patient, and area of body surface to which the heat is applied. Moist heat is more penetrating than dry heat. Prolonged applications of heat produce an increase in skin secretions, resulting in a softening of the skin and a lowering of its resistance. Extreme heat produces constriction of the blood vessels; moderate heat produces vascular dilation. Repeated applications of heat will result in an increased tolerance to heat so that the individual may be burned without being aware of it. Elderly persons and infants are more susceptible to burns from high temperatures.

Heat applied to an infected area can localize the infection; for this reason, external heat should not be applied to the abdomen when appendicitis is suspected, because it may lead to rupture of the inflamed appendix.
heat exhaustion a disorder resulting from overexposure to heat or to the sun; long exposure to extreme heat or too much activity under a hot sun causes excessive sweating, which removes large amounts of salt and fluid from the body. When salt and fluid levels fall too far below normal, heat exhaustion may result. Called also heat prostration.
Symptoms. The early symptoms are headache and a feeling of weakness and dizziness, usually accompanied by nausea and vomiting. There may also be cramps in the muscles of the arms, legs, or abdomen. These first symptoms are similar to the early signs of sunstroke, or heat stroke, but the disorders are not the same and should be treated differently. In heat exhaustion, the person turns pale and perspires profusely. The skin is cool and moist, pulse and breathing are rapid, and body temperature remains at a normal level or slightly below (in sunstroke the body temperature may be dangerously elevated). The patient may seem confused and may find it difficult to coordinate body movements; loss of consciousness seldom occurs.
Treatment. In cases of heat exhaustion, the victim should lie quietly in a cool place until transported to an emergency facility. The restoration of normal blood volume will be a priority. Stabilization of electrolytes is also important. If the person is able to safely swallow, sips of cool replacement fluid should be provided. Measures to reduce body temperature are employed.

If the condition is accompanied by cramps, the pain may be relieved by lightly stretching the affected muscles in addition to administering replenishing fluids. In cases of severe heat exhaustion and cramps, hospitalization may be necessary. Serum electrolyte levels are monitored to guide adequate replacement.
Prevention. Heat exhaustion and other heat disorders may be prevented by avoiding long exposure to sun or heat. The elderly, the very young, individuals with chronic diseases, and athletes exercising in the sun are at high risk. When the weather is very hot, or when working in an extremely hot place, it is essential to maintain adequate hydration. Regular rest periods are necessary. In the event of weakness or dizziness, persons should stop working at once and rest in a cool place.

It is possible for indoor temperatures to exceed the outdoor temperature. Poor ventilation can lead to an unhealthy situation that contributes to heat exhaustion. For this reason, adequate temperature control indoors is important in prevention of serious health problems.
latent heat the amount of heat absorbed or given off by a body without changing temperature, as when it undergoes a change of state.
prickly heat (heat rash) miliaria.
specific heat the ratio of the heat capacity of a substance to that of water; it is equivalent to the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius, since the corresponding value for water is defined as 1.0.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

heat ex·haus·tion

a form of reaction to heat, marked by prostration, weakness, and collapse, resulting from severe dehydration.
Farlex Partner Medical Dictionary © Farlex 2012

heat exhaustion

A condition caused by exposure to heat, resulting in the depletion of body fluids and causing weakness, dizziness, nausea, and often collapse. The condition can be alleviated by rest and the administration of fluids and electrolytes to compensate for those lost through excessive sweating. Also called heat prostration.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

heat stress disease

Critical care A group of conditions due to overexposure to or overexertion in excess environmental temperatures
Heat stress-forms in increasing severity
Heat cramps Non-emergent and treated by salt replacement
Heat exhaustion More serious, treated with fluid and salt replacement
Heat stroke Most commonly affecting extremes of ages, especially the elderly, accompanied by convulsions, delusions, coma and treated by cooling the body and replacement of fluids and salts
Note: The body's reaction to heat is a function of controllable–use of anticholinergics, phenothiazines, alcohol, heavy exercise, clothing, obesity, direct exposure and acclimatization and uncontrollable factors–high ambient temperatures or humidity, lack of air circulation, underlying fever, old age or infancy, ectodermal dysplasia  
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

heat ex·haus·tion

(hēt eg-zaws'chŭn)
A form of reaction to heat marked by prostration, weakness, and collapse, resulting from severe dehydration.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

heat exhaustion

A disorder usually caused by undue exertion in a hot climate with inadequate water and salt intake. Heat exhaustion features severe weakness, headache, nausea, sweating, vertigo, collapse and failure of the peripheral circulation from loss of fluid content in the blood. Treatment involves urgent fluid and salt replacement.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

heat exhaustion

the failure of cooling mechanisms resulting from an excessive rise in body temperature in warm-blooded animals, characterized by cramp and dizziness.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Monitor your personal condition and anyone that is outside with you for symptoms that may indicate heat exhaustion or heatstroke

"While heat exhaustion can be easily managed and prevented from reaching the heat stroke stage, once that stage happens, it becomes difficult to treat," said Dr Cheriyan.
Coaches must understand that heat exhaustion, when left untreated, can lead to heat stroke -- a significantly more dangerous condition.
No matter what age you are, you can get overheated very quickly and the move from heat exhaustion to heat stroke can happen a whole lot faster than many people appreciate," Dr.
Well-placed sources told the GDN that the spate of cases was registered on Monday and Tuesday at Salmaniya Medical Complex (SMC), in which labourers working at outdoor worksites during the hottest hours of the day suffered fatigue and heat exhaustion.
Al Ansari, around 25 children in Qatar were treated at HMC in 2016 for heat exhaustion and heat stroke.
According to Pagasa, a heat index of 32 degrees to 41 degrees calls for 'extreme caution,' exposure to which could cause heat cramps and heat exhaustion. Continuing activity in such hot conditions could result in heat stroke.
Of the cases we receive, most are heat exhaustion cases, and very few are heat strokes."
Workers should also take a break to prevent heat exhaustion," they said.
Though many GCC countries have implemented work bans during peak hours, which have helped reduce the risk of accidents, heat exhaustion and heat stroke, the risks remain for anyone exposed to the intense summer temperatures for prolonged periods.
HEAT EXHAUSTION: If you start getting a headache, feel nauseous, have pale clammy skin, cramps or a rapid, weakening pulse - you may be suffering from heat exhaustion.
Hundreds of outdoor workers visited a major hospital in Bahrain for heat exhaustion in the last week, sparking a call by health officials for employers to take a proactive approach towards protection of their workers against the rising heat.