1. energy that raises the temperature of a body or substance.
3. a rise in temperature.
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.
. Heat Production.
Body heat is the byproduct of the metabolic processes of the body. The hormones thyroxine
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
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.
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
. 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.
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.
a temporary eruption on the skin.
butterfly rash a skin eruption across the nose and adjacent areas of the cheeks in the pattern of a butterfly, as in lupus erythematosus and seborrheic dermatitis. (See Atlas 2, Part B).
in the area in contact with the diaper in infants, often sparing the genitocrural folds, occurring as a reaction to prolonged contact with urine and feces, retained soaps and topical preparations, and friction and maceration, and commonly associated with secondary bacterial and yeast infections, especially with Candida albicans
. Some consider irritation by the ammoniac decomposition products of urine to be a contributing factor. Called also diaper dermatitis.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
rash (rash) [Fr. rasche, skin eruption]
A general term for any eruption that appears on the skin transiently (as opposed to durable skin lesions such as scars, tattoos, or moles). Synonym: exanthem
Assessments are made of the location and characteristics of the lesion: color; size (height and diameter); pattern, whether discrete or coalesced; and any secondary changes (crusting, scaling, lichenification). Associated symptoms such as pruritus or discomfort, temporal elements, history of known allergies, drugs used, and contacts with communicable diseases during prior 2-week period also are assessed. Suspected drugs are discontinued, and the potential communicable disease patient is isolated and assessed. Cool compresses are applied to relieve itching. Topical preparations and dressings are applied and systemic medications administered as prescribed. The patient is instructed to keep hands clean and nails short and even, and to avoid scratching. The patient also is taught about the treatment regimen, its actions, and its side effects and evaluates for desired effects and side effects.
A rash on both cheeks joined by an extension across the bridge of the nose. It is seen in systemic lupus erythematosus, esp. after the patient's face has been exposed to sunlight, and in seborrheic dermatitis, tuberous sclerosis, and dermatomyositis. See: discoid lupus erythematosus
DIAPER RASH: (A) mild diaper rash, (B) severe yeast infection in diaper area
Irritant contact dermatitis as a reaction to friction, maceration, and prolonged contact with urine, feces, soap retained in diapers, and topical preparations. A persistent diaper rash may be colonized by yeast or bacteria. Synonym: diaper dermatitis
Treatment is symptomatic. Diapers should be changed frequently. If washable cloth diapers are used, they should be thoroughly washed and rinsed; occlusive plastic pants should not be used over diapers; the perianal and genital areas should be washed with warm water and mild, nonperfumed soap. If these measures and the application of a bland protective agent (such as zinc oxide paste) do not promote healing, then a small amount of 0.5% to 1% topical hydrocortisone cream should be applied to the area after each diaper change until the rash has completely resolved.
drug rashDrug eruption.
ecchymotic rashHemorrhagic rash.
A red papular eruption on an infant's chin and anterior chest area seen during teething. It is a form of miliaria due to excess saliva coming in contact with the skin. Synonym: red rash; tooth rash
heat rashPrickly heat.
A rash consisting chiefly of bleeding or bruising into or under the skin. Synonym: ecchymotic rash
A rash in which the lesions are flat and level with the surrounding skin.
A rash in which there are discrete macular and papular lesions or a combination of both.
A rash caused by local application of mercurial preparations.
A dusky rash seen in typhus.
red rashGum rash.
A pruritic hivelike rash (urticaria or angioedema) or a vasculitis (palpable purpura) that accompanies serum sickness, usually caused by a hypersensitivity reaction to drugs or immune globulins obtained from animals. Malaise, joint pains, fevers, and other symptoms may accompany the rash. See: serum sickness
splash rashHot tub folliculitis.
A macular rash resembling the reddened skin characteristic of a severe sunburn. See: exfoliative dermatitis; toxic shock syndrome
tooth rashGum rash.
wandering rashGeographic tongue.
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