OVERHEATING OF THE ORGANISM

From Big Medical Encyclopedia

OVERHEATING OF THE ORGANISM (synonym hyperthermia) — the condition of an organism which is characterized by disturbance of a heat balance, increase in heat content of an organism. The item of the lake arises under the influence of high temperature of the environment, and also factors complicating return to the environment of the heat which is constantly formed in an organism or coming to it from the outside. The main way of a thermolysis at P. of the lake of the person — evaporation of moisture from a body surface and respiratory tracts. By the item of the lake it is not connected with primary dysfunction of thermal control.

The item of the lake of the person is observed on productions with high temperature of the environment or in the conditions complicating a thermolysis from a body surface and also in districts with hot climate. At high temperature of the environment of P. of the lake promote growth of the heat production arising during the muscular work, especially in clothes, impenetrable for water vapors, high humidity and an immovability of air. In difficult conditions for a thermolysis children of early age easily overheat, at to-rykh the system of thermal control, and also adults with the broken function of sweating is insufficiently created.

Artificially caused hyperthermia can be applied to treatment of nek-ry diseases (see. Pyrotherapy ) and as a functional trial for definition of stability of an organism and it fiziol. functions to overheating, napr, at professional selection of mine rescuers.

The mechanism of action on an organism of different types of heat

the Mechanism of action on an organism of different types of heat (convection, conduction, radiation) is not identical. Convection and conduction heat, being transferred from a molecule to a molecule, causes superficial heating of fabrics and the blood circulating in them, edges are transferred by heat to deeper fabrics and bodies. Radiation heat (infrared radiation of various spectral structure and intensity) can deeply get into tissues of the person and an animal. Releaser of reactions physical and chemical thermal controls (see) the thermal irritation skin and vascular is thermoreceptors (see) with the subsequent response to it of the center of thermal control. At considerable P. of the lake change fiziol, functions happens also owing to effect of heated blood on c. N of page. At ambient temperature above comfortable (i.e. temperatures, at a cut functional activity of systems of an organism is in limits fiziol, norms) blood vessels of skin extend, their krovenapolneniye increases, temperature of skin increases. The weighted average temperature of skin (temperature of skin taken at the same time in several points taking into account the area of each site of a body surface) 34 — 35 ° is border of comfortable heatfeeling; exceeding leads it to discomfort and active secretion of sweat (see. Sweating ).

As a result of temperature increase of the environment the thermolysis radiation, convection, a conduction decreases and the thermolysis evaporation of moisture from a body surface increases (see. Thermolysis ). According to a number of researchers, at temperature increase of an ambient air from 16 to 30 ° and moderately severe work at the dressed person the share of a thermolysis as convection and radiation decreases from 73 to 8% of the total value of a thermolysis, and the thermolysis evaporation of moisture increases from 27 to 92%. Heat output from a body surface convection and radiation stops at ambient temperature apprx. 33 °.

Indicators of thermal exchange at the person (inspected at rest, dressed in a summer suit at t ° 30 — 80 °, relative humidity of 15 — 25%, the speed of the movement of air of 0,2 — 0,3 m/s): 1 — heat production of an organism, 2 — thermal storage in an organism, 3 — a thermolysis evaporation of moisture, 4 — external thermal loading, 5 — the general thermal loading; on abscissa axis — ambient temperature, on ordinate axis — heat energy.

The conducted researches of action of high temperatures on the nature of changes of thermal exchange (fig.), cardiovascular and respiratory systems allowed to allocate four degrees of P. of the lake for a human body (inspected were in summer suits, at rest, at t ° 30 — 80 °, relative humidity of 15 — 25%, the speed of the movement of air 0,2 — 0,3m/sec.). This classification is offered by A. N. Azhayev.

The I degree of P. of the lake (so-called steady adaptation) is observed at ambient temperature apprx. 40 °; at the same time the thermolysis is carried out only by evaporation of moisture from a body surface and respiratory tracts. So far the thermolysis is equal to the general thermal loading developing of heat production of an organism (see. Heat production ) and external thermal loading, heat content of an organism and body temperature do not increase. At temperature increase of a body surface, napr, at the complicated evaporation of sweat, heat content in an organism can increase also at the I degree of P. of the lake, and body temperature can reach 37,5 °, there is a nek-swarm a decrease in the ABP (systolic and diastolic), lung ventilation, oxygen consumption and release of carbonic acid; the minute volume of heart increases, pulse becomes frequent on 15 — 20 beats/min; the hyperemia and moistening of skin is observed. The general satisfactory condition, complaints generally come down to a caumesthesia, are quite often noted, slackness and drowsiness, unwillingness to work and move.

The II degree of P. of the lake (so-called partial adaptation) arises at ambient temperature apprx. 50 °, at the same time the general thermal loading is not compensated by evaporation of moisture any more, and thermal storage in an organism happens owing to the termination of return to the environment of heat which is formed in an organism. Body temperature can reach 38,5 °; systolic pressure increases by 5 — 15 mm of mercury., and diastolic — decreases by 10 — 20 mm of mercury.; the minute and systolic volume of heart, lung ventilation, amount of absorbed oxygen and the emitted carbonic acid increase; pulse becomes frequent on 40 — 60 beats/min; the sharp dermahemia, profuse sweating, feeling of a heat are observed.

The III degree of P. of the lake (so-called failure of adaptation) is observed at influence of high temperatures St. 60 °, at the same time external thermal loading prevails over a thermolysis evaporation of moisture from a body surface and respiratory tracts. Increase in heat content of an organism comes owing to the difficulty of heat output which is formed in an organism and receipt it from the environment. Body temperature can reach 39,5 — 40 °, systolic pressure increases by 20 — 30 mm of mercury., and diastolic decreases by 30 — 40 mm of mercury., the effect of «infinite tone» (zero diastolic pressure) can be listened. Relative reduction of systolic volume of heart at the continuing increase of cordial reductions is observed. At a considerable part inspected (steady against overheating), despite decrease in systolic volume of heart, minute volume continues to increase due to increase of cordial reductions. Lung ventilation amplifies, the amount of absorbed oxygen and the emitted carbonic acid increases. Pulse becomes frequent twice and more in comparison with initial size, reaching on average 160 beats/min. The health worsens that is shown in feeling of a strong heat, heartbeat, a pulsation and pressure in temples, quite often weight in the head and a headache. Excitement, motive concern is noted; skin is sharply hyperemic, sweat flows down drops, the strengthened cardiac impulse, a pulsation of carotid and temporal arteries is observed. At

At the IV degree of P. of the lake (so-called lack of adaptation) limit thermal storage in an organism can average 80 kcal on 1 m 2 body surfaces, or 2 kcal on 1 kg of the weight (weight) of a body; at the persons steady against overheating, it reaches 95 — 100 kcal on 1 sq.m of a body surface, or 2,3 — 2,5 kcal on 1 kg of body weight. At the IV degree of P. of the lake there is a disturbance of activity of cardiovascular system and ts.n.s. (see. Thermal shock ).

P.'s degree of the lake depends on duration of influence of high temperature: I, II, III degrees of P. of the lake arise at temperatures apprx. 40 °, 50 °, 60 ° within 140, 120, 100 min. according to. However at t ° 40 °, influencing within 180 min. and more, there can be the II degree of P. of the lake; at t ° 50 ° and 60 ° within respectively 300 — 350 and 120 — 180 one or III min. P.'s degree of the lake. At ambient temperature 70 and 80 °, influencing respectively within 70 — 100 and 40 — 60 min., the IV degree of P. of the lake is observed.

High humidity and an immovability of air, physical activity, vapor-tight clothes and other factors, and also disturbances of a functional condition of an organism, its systems and separate bodies, e.g. a thyroid gland, considerably accelerate P. of the lake. So, patients with a thyrotoxicosis are less steady against action of high temperature.

At P. of the lake in most cases the respiration rate practically does not change, at persons (is more often at full), high temperatures, less steady against influence, small increase of breath is found (from 18 to 29 dykhaniye in 1 min.); lung ventilation (see) increases generally at the expense of depth of breath. Only hard physical activity at high temperature of the environment causes increase of breath to 40 — 50 dykhaniye in 1 min.

At the person at P. of the lake tension of CO changes 2 and O 2 in blood, and also acid-base equilibrium. At ambient temperature 70 ° pH of blood (at rest) increases on 0,07; tension of carbonic acid in blood decreases by 25%, oxygen — at 7,4% of initial sizes. Washing away of carbonic acid from an organism, except a hyperventilation of lungs, is promoted also by decline in the ability of blood to connect CO 2 at increase in its temperature. Undervoltage of oxygen in blood at P. of the lake is a consequence of circulator disturbances in cardiovascular system. It is possible that a certain value in emergence of an anoxemia during the overheating has expansion of a capillary and venous bed of skin and decrease in extent of dissociation of oxyhemoglobin because of washing away of carbonic acid and change of pH of blood towards an alkalosis.

At long stay in conditions of elevated temperature the human body loses a significant amount of water preferential in the form of urine and sweat (see. Dehydration of an organism ). At residents of Central Asia in the summer the bigger amount of water is removed with then, and release of urine makes 0,3 — 0,6 l a day (at norm apprx. 1,5 l). At the healthy person the condition of water exhaustion comes after loss of 5 — 6% of initial body weight. Loss more than 10% of water leads to the symptoms menacing for life (to a so-called desert disease).

At the persons working at high temperature of the environment despite the strengthened water consumption, deficit of body weight because of considerable sweating and reduced appetite is observed. Weight reduction of a body for 3 — 4% of initial can come during the summer period of year at bystry movement of the person from the area with a temperate or frigid climate in hot. On vodnosolevy exchange high temperature in the first week of stay of the person in hot climate has adverse effect, in the subsequent thirst and water loss from a body surface decreases, the amount of urine increases. The size of sweating, except ambient temperature, is influenced also by humidity and speed of the movement of air, degree of physical tension, heat-insulating qualities of clothes.

With temperature increase of the environment from 30 ° to 80 ° the general moisture loss of an organism increases, at the same time the amount of not evaporated sweat (profuse sweating) increases. At low air humidity considerable reduction of effective sweating (the relation of moisture loss by evaporation to the general of moisture loss expressed as a percentage) is noted at £ °55 — 60 °. At relative humidity of air, the equal 80 — 90%, these changes come already at £ °35 ° and 40 °. Sweating is followed by removal from an organism of organic and inorganic matters. Main component sweat (see) water, and from dense substances — sodium chloride is.

Depletion of an organism water is shown by feeling thirst (see), a cut is followed by dryness of lips, oral cavities and drinks. Thirst arises at the losses of water making 1 — 2% of body weight. At this degree of dehydration concentration of sodium chloride in blood begins to decrease. Changes physical. - chemical properties of blood, coming owing to depletion of an organism water, exert impact on the drinking center, supporting its excitement. Water content in tissues of a brain and heart at influence of high temperatures almost does not change. It is promoted by redistribution of water in intestines, skin, muscles, to-rye deposit water and salts and by that promote their preservation in an organism for needs of thermal control.

The mechanism of action of high temperatures is investigated on animals; it has the features. So, a thermal asthma (polypnea) is characteristic of dogs, the edge at the person is not observed. The polypnea is less effective device of physical thermal control in comparison with function of the sweat glands playing the main role in a thermolysis of an organism at the person, primacies and one-hoofs. Lack of sweat glands at a dog and other animals causes rather weak resilience them to overheating. At superheated dogs the considerable hyperventilation leads to a hypocapny and shift of pH of blood towards an alkalosis (loss of C02 up to 50 — 60%, increase in pH of blood on 0,2 — 0,3). Gipertireoidizirovan-ny animals are less steady against action of high temperature, and ti-reoidektomirovanny animals transfer P. of the lake easier, than gipertireoi-dizirovanny.

At emergence of overheating it is necessary to liquidate the conditions which caused it. At emergence of the IV degree of P. of the lake medical aid is necessary (see. Thermal shock ).

Prevention

P.'s Prevention by the lake consists in the prevention of loss by an organism of water and salts. For working at high temperature of the environment the water-salt mode is developed. At a lose of weight of a body more than 4 — 4,5 kg (for a 8-hour shift) additional reception of sodium chloride is recommended. Water consumption shall be sufficient for a satisfying of thirst; it is considered fractional .priy waters in small amounts most expedient (see. Drinking mode ). The population of Central Asia has green tea, to-ry more slowly in the summer, than black, is brought from an organism, being good adipsous means. During reception of hot tea evaporation of water from a body surface is much higher, than at consumption of cold tea. The best condition of a water salt metabolism is reached at the use of carbohydrate and carbohydrate and proteinaceous food; according to a number of researchers, it promotes smaller water consumption and its bigger delay in an organism. Due to the oppression at P. dry and fresh fruit and vegetables decoctions, and also kvass, a fruit drink and tomato juice are recommended to the lake of secretory and motor function of a stomach and intestines; at the same time preference is given to easily digested products. In districts with hot climate it is necessary to consider selectivity of appetite — acute, spicy snack, borsch, Russian cabbage soup from fresh or salty cabbage, okroshka, beetroot soup, fried potatoes, stewed vegetables, compote, lactic products are better eaten. Working in the conditions of high temperatures it is desirable to reduce the caloric content of a lunch, having increased the caloric content of a dinner or breakfast. For the prevention of overheating and dehydration of an organism arrived in the summer to the district with hot climate from other climatic zones and performing physical activity in the open air during an initial stage acclimatization (see) shall be under the strengthened medical control (thermometry, weighing).

Short-term rest (10 — 15 min.) in the places protected from direct solar radiation near the place of work (canopies, tents, and also the figurative lodges or motor vans supplied with fans, conditioners, shower installations) is periodically necessary for protection against adverse action of high temperatures working in the open air. For protection against direct solar radiation of a window of rooms are equipped with wide eaves and visors. Workers shall be provided in enough with drinking water, drinks, and also vozdu-ho-and vapor-permeable overalls. Reasonablly to plan work for cool morning and evening hours in the open air, and the hottest time of day (from 13 to 16 hours) to take away for rest and work indoors.

For P.'s prevention by the lake in production rooms with high temperature spraying of water is recommended and having blown in air. Restrooms should be equipped with panel cooling or air conditioning system and ventilation.

Overheating of an organism at children.

Tendency of children unlike adults to overheating, especially newborns and children till 1 year of life, is explained by feature of their heat exchange and thermal control. Throughout all children's age evolution of processes of heat exchange is observed, edges consists not only in change of heat generation and a thermolysis, but also in gradual development of the central mechanisms of thermal control. At newborn children of reaction of chemical thermal control are rather developed; reactions of physical thermal control are presented poorly, fever is a little expressed (is atypical) and rises in temperature are more often connected with P. the lake. With age regulation of heat exchange becomes more economic and purposeful.

Overheating of an organism at babies is promoted by temperature increase of air and excessive wrapping, seniors have a long stay in the hot, stuffy room, right in the sun (the conditions complicating a thermolysis), steady physical stress, napr, tourist campaigns, page - x. works without the corresponding equipment, and other conditions influencing increase in heat generation.

Stay of children at the age of 6 — 7 years indoors with air temperature 29 — 31 ° and walls 27 — 28 ° during 6 — 8 hours causes temperature increase of their body to 37,1 — 37,6 °. Solar overheating proceeds with dominance of primary disturbances from c. the N page, and fervescence has important, though not paramount value.

At babies of P. of the lake it is shown by slackness, a sharp adynamia, a sleep disorder, a loss of appetite, vomiting, in some cases frustration went. - kish. path; at survey the hyperemia of integuments, perspiration, increase of breath and pulse rate, muting of cardiac sounds and decrease in the ABP is noted. At children of more advanced age the headache, dizziness, the general weakness, drowsiness, fatigue, block is observed, nausea, vomiting, spasms, a short-term loss of consciousness are possible, there can be fervescence to 40 — 41 °.

Islands carry out differential diagnosis of P. with a feverish hyperthermia (see. Hyper thermal syndrome ), at a cut symptoms of an acute infection usually come to light, and fervescence is connected with a fever and primary restriction of a thermolysis. During the overheating along with the increased heat production increase in a thermolysis, sweating is observed, etc.

Treatment

P.'s Treatment by the lake is directed first of all to fight against a hyperthermia and normalization of activity of cardiovascular system: wet packs, at spasms — cold on the head, bathtubs with a temperature not lower than 37 °. Plentiful drink is recommended: to children up to 2 years at the rate of 100 — 130 ml on 1 kg of weight; to the senior children — 3 — 4 l a day. Solution of glucose, Ringer's solution enter parenterally together with vitamins. At a collapse the oxygenotherapy and administration of adrenaline subcutaneously are shown; at acute cardiovascular insufficiency — administration of intravenously cardiac glycosides (box-g of l an icon, strophanthin), and also the hyposensibilizing means. The milk and vegetable Diet is recommended.

Prevention consists in elimination of the reasons causing P. of the lake.


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A. H. Azhayev; I. P. Bryazgunov (ped.).

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