heat exhaustion

exhaustion /ex·haus·tion/ (eg-zaws´chun)

1. a state of extreme mental or physical fatigue.

2. the state of being drained, emptied, or consumed.

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heat exhaustion  an effect of excessive exposure to heat, marked by subnormal body temperature with dizziness, headache, nausea, and sometimes delirium and/or collapse.

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heat exhaustion

n.

A condition caused by exposure to heat, marked by prostration, weakness, and collapse, resulting from unrecognized or unavoidable dehydration. Also called heat prostration.

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heat exhaustion,

an abnormal condition characterized by weakness, vertigo, nausea, muscle cramps, and loss of consciousness, caused by depletion of body fluid and electrolytes that results from exposure to intense heat or inability to acclimatize to heat. Body temperature is near normal; blood pressure may drop but usually returns to normal as the person is placed in a recumbent position. The skin is cool, damp, and pale. The person usually recovers with rest and replacement of water and electrolytes. Also called heat prostration. Compare heat hyperpyrexia. See also heat cramp.

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exhaustion [eg-zaws´chun]

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.

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heat [hēt]

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.

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exhaustion

privation of energy with consequent inability to respond to stimuli; lassitude.

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heat exhaustion

an effect of excessive exposure to heat. See also heat exhaustion.

physical exhaustion

occurs most commonly in horses engaged in endurance or marathon events. Also in males engaged in territorial combats; bulls and boars are the usual combatants. There are some lacerations but exhaustion is the main problem. Manifested by lethargy, dehydration, hyperthermia, hyperpnea, tachycardia, muscle tremor and some muscle spasm, restlessness, anal relaxation, unwillingness to stand, fidgeting while down, pale cyanotic mucosa and poor capillary refill time.

exhaustion syndrome

in a fit horse normal levels of function in the cardiopulmonary system should be regained within 30 to 60 minutes of stopping work. This is unlikely with horses that are exhausted and which have the following clinical signs—lethargy, dehydration, hyperthermia, hyperpnea, tachycardia, muscle tremor, restlessness, relaxation of the anal sphincter, reluctance to stand, pale mucosa, poor capillary refill and a respiratory to cardiac rate ratio of greater than 2:1. Called also exhausted horse syndrome.

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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