Hypothermia is a pathological decrease in the central body temperature in men or women (including a newborn), to a level below 35 degrees. The condition is extremely dangerous for a person's life (we are not talking about complications): if you do not provide a person with medical care, death occurs.
The usual temperature indicator of 36.6 degrees is the norm only for the peripheral temperature shell. The central temperature is always higher - 38 degrees, and this is the optimal indicator. So when it happens general hypothermia, the lifespan of brain neurons is sharply reduced, which leads to extremely Negative consequences for human health. In such cases, you must provide urgent Care. The slightest delay can lead to death.
Premature newborns are at risk. In general, age and gender restrictions are given pathological process, of course, does not - certain types of hypothermia can be diagnosed at any age.
In the presence of a pathological process in an adult or a newborn, it is urgent to call an emergency medical team and, along the way, carry out measures to provide first aid. Do not give any drugs, even if the symptoms and signs clearly indicate hypothermia.
Further prognosis will depend on the severity of hypothermia, the age and general clinical parameters of the victim. Extremely negative forecasts will be if there is hypothermia in newborns and in pregnant women - the risk of death is very high. Local hypothermia can lead to tissue necrosis and, as a result, the loss of the affected area of the body (most often it is the limbs). Easy stage hypothermia can lead to pneumonia and other diseases.
By international classification diseases of the tenth revision, hypothermia has its own separate code: ICD-10 code - T68. It should be noted that the concepts of hypothermia and are different things.
Etiology
The optimal body temperature is maintained due to the balance of heat production, that is, the ratio of heat transfer and heat production is observed. If heat transfer prevails over heat production, hypothermia begins.
The main causes of hypothermia:
- prolonged exposure to cold or immersion in cold water at minus or zero body temperature;
- volumetric infusion of cold solutions;
- volumetric infusion of whole blood and drugs;
- prolonged regional or general anesthesia.
In addition to pathological hypothermia, therapeutic or intraoperative hypothermia can occur in men and women of any age, the causes of which are as follows:
- heart failure;
- during heart operations;
- complications of asphyxia;
- brain injury that provoked a neurogenic fever;
- severe damage to the central nervous system;
- neonatal hypoxia.
Neonatal hypothermia is extremely life-threatening, so urgent therapeutic measures are required.
The risk group and predisposing factors for the development of such a pathological process should be identified:
- persons under the influence of alcohol low temperature environment;
- people with poor circulation;
- children;
- aged people;
- immobilized or unconscious.
Separately, it should be said that in men, during hypothermia, the most vulnerable groin area.
Regardless of what caused the development of the pathological process, the victim needs urgent therapeutic measures.
Classification
Physiology distinguishes the classification of the pathological process according to several criteria. Hypothermia in children and older people is divided into several stages depending on the severity of the pathological process:
- light - 35.0–35.2 degrees Celsius;
- medium - 27–32.1 degrees Celsius;
- severe - body temperature is less than 27 degrees Celsius.
The disease in children and older people is divided into two types - moderate and severe. With a moderate form of hypothermia, the patient retains the ability to independently passive or active warming. In a severe form of the pathological process, this is not possible, which means that the risk of death is significantly increased.
Symptoms
The clinical picture will depend on the stage of hypothermia. The mild stage will be characterized by the following symptomatic complex:
- disorientation in space and time;
- lethargy;
- drowsiness;
- rapid breathing;
- muscle tremors;
- impaired coordination of movements;
- low or high blood pressure.
The average form of hypothermia will be characterized by the following clinical picture:
- confusion;
- violation of breathing and heart rhythm;
- trembling in the body;
- violation of coordination of movement;
- slowing down metabolic processes;
- the presence of nausea and vomiting in a child and an adult;
- decrease in mental activity.
At this stage of hypothermia, a person may still be conscious, but for a newborn, this body temperature can be critical. This is especially dangerous during pregnancy.
Signs of hypothermia in the last stage are characterized as follows:
- there is no pupillary reaction to light;
- no tendon reflexes;
- blood pressure drops to critical levels;
- the amount of urine excreted increases;
- frequency respiratory movements reduced to 8-10 per minute;
- symptomatology;
- expressed.
General hypothermia is extremely life-threatening: if a person is not provided with medical assistance in the next few minutes, there is a high probability of death.
Diagnostics
The main diagnostic measure for hypothermia in children and adults is temperature measurement. However, it should be noted that the measurement of the thermal state of the body is not carried out in the traditional way, but with the help of special electronic thermometers in the following places:
- outdoor ear canal;
- in the rectum;
- in the groin area;
- in the nasopharyngeal region.
The following diagnostic measures are carried out:
- blood sampling for general and biochemical analysis;
- general analysis urine;
- daily measurement of the frequency of diuresis;
- blood tests for electrolyte levels and acid-base balance;
- coagulogram;
- pulse oximetry;
- daily measurement of blood pressure;
- CT or MRI of the brain;
- radiographic study.
In pregnant women, X-rays are performed only in exceptional cases.
Treatment
Treatment will depend on what form of the pathological process has been diagnosed. Required first aid with hypothermia.
First aid for hypothermia includes the following activities:
- If the patient is conscious, it is necessary to give a hot drink and cover with a warm blanket. The victim must be in a dry place and in dry clothes.
- The patient should be warmed up gradually.
- A heating pad or a bottle of warm water should be applied to the body.
- The body and head must be covered dry and warm cloth, clothes.
- If the patient felt sick, after vomiting, turn the person on his side and give warm water. You can't leave him alone.
Important: do not give alcohol and try to warm the victim immediately and completely - this can lead to the development of complications and cardiac arrest. Along with the provision of first aid, a medical team should be called. Reception of antipyretics and other medicines is prohibited.
Treatment of the pathological process in men and women may include the following activities:
- inhalation with warm and moist air;
- intravenous infusion warm crystalloid solution;
- lavage of the stomach, bladder and intestines with a warm solution;
- lavage chest;
- lavage abdominal cavity warm dialysate.
During events, active warming stops if the central temperature reaches 34 degrees Celsius. During the medical measures ECG control is carried out, as there is a high risk of heart rhythm disturbance, which is very dangerous during pregnancy and for the elderly.
Surgical intervention is not excluded if hypothermia of the hands, feet on late stages and, as a result, tissue necrosis.
During pregnancy, the most sparing tactic of therapy is chosen, since the life of not only the mother, but also the child is at risk. If treatment is started in a timely manner and at a mild to moderate stage of the pathological process, complications can be avoided.
Possible Complications
Complications of hypothermia:
- if the inguinal region was affected during hypothermia - the development of diseases from genitourinary system;
- that leads to death;
- Heart arythmy;
- hypovolemic shock.
Most of the consequences can be avoided if therapeutic measures are started in a timely manner.
Prevention
Prevention of hypothermia is as follows:
- dress according to the weather;
- since the inguinal region of a person is especially vulnerable, warm underwear should be worn in cold weather;
- use only dry clothes and shoes;
- if you need to stay in the cold for a long time, be sure to periodically go into a warm room and drink hot more often;
- do not drink alcohol in case of hypothermia or prolonged exposure to the open air at low temperatures;
- strengthening the immune system.
The causes of hypothermia are well known to everyone, so it is enough to simply prevent the development of pathology.
The hypothermic ones are conditions characterized by a decrease in body temperature below normal. Their development is based on the breakdown of thermoregulation mechanisms that ensure the optimal thermal regime of the body. There are cooling of the body (actually hypothermia) and controlled (artificial) hypothermia, or medical hibernation.
Hypothermia- a typical form of heat metabolism disorder - occurs as a result of exposure to low temperature on the body external environment and / or a significant decrease in heat production in it. Hypothermia is characterized by a violation (disruption) of the mechanisms of thermoregulation and is manifested by a decrease in body temperature below normal.
Causes development of body cooling are diverse.
- Low temperature the external environment (water, air, surrounding objects, etc.) is the most common cause of hypothermia. It is important that the development of hypothermia is possible not only at negative (below 0 °C), but also at positive external temperatures.
- Extensive muscle paralysis and / or a decrease in their mass (for example, with their malnutrition or dystrophy). This may be caused by trauma or destruction (eg, post-ischemic, syringomyelia, or other pathological processes) spinal cord, damage to the nerve trunks innervating the striated muscles, as well as some other factors (for example, Ca 2+ deficiency in the muscles, muscle relaxants).
- Metabolic disorders and / or decrease in the efficiency of exothermic metabolic processes. Such conditions most often develop with adrenal insufficiency, leading (among other changes) to a deficiency in the body of catecholamines, with severe hypothyroid conditions, with injuries and dystrophic processes in the centers of the sympathetic nervous system of the hypothalamus.
- The extreme degree of exhaustion of the body.
The pathogenesis of hypothermia
The development of hypothermia is a staged process. Its formation is based on a more or less prolonged overvoltage and, as a result, a breakdown of the body's thermoregulation mechanisms. In this regard, in hypothermia, two stages of its development are distinguished: 1) compensation (adaptation) and 2) decompensation (deadaptation). Some authors distinguish the final stage of hypothermia - freezing.
Stage of compensation . The compensation stage is characterized by the activation of emergency adaptive responses aimed at reducing heat transfer and increasing heat production.
Stage of decompensation (deadaptation) thermoregulation processes is the result of a breakdown central mechanisms regulation of heat exchange.
At the stage of decompensation, the body temperature falls below the normal level (in the rectum it drops to 35 ° C and below) and continues to decrease further. Temperature homeostasis of the body is disturbed - the body becomes poikilothermic.
MANAGED HYPOTHERMIA (MEDICAL Hibernation)- a method of controlled decrease in body temperature or part of it in order to reduce the intensity of metabolism, the level of function of tissues, organs and their physiological systems, increasing their resistance to hypoxia.
In case of violation heat balance organisms develop either hyperthermic or hypothermic states. Hyperthermic states are characterized by an increase, and hypothermic states - by a decrease in body temperature above and below normal, respectively.
HYPERTHERMAL CONDITIONS
Hyperthermic conditions include overheating of the body (or hyperthermia itself), heat stroke, sunstroke, fever, and various hyperthermic reactions.
Actually hyperthermia
Hyperthermia- a typical form of a disorder of heat exchange, resulting, as a rule, from the action of a high ambient temperature and a violation of heat transfer.
ETIOLOGY Causes of hyperthermia
There are external and internal causes.
High ambient temperatures can affect the body:
♦ in a roast summer time;
♦ in production conditions (in metallurgical and foundry plants, in glass and steel making);
♦ during fire suppression;
♦ with a long stay in a hot bath.
The decrease in heat transfer is a consequence of:
♦ primary disorder of the thermoregulation system (for example, if the corresponding structures of the hypothalamus are damaged);
♦ violations of heat transfer in environment(for example, at obese people, with a decrease in the moisture permeability of clothing, high humidity).
Risk factors
♦ Effects that increase heat production (intensive muscular work).
♦ Age (hyperthermia develops more easily in children and the elderly, who have reduced the efficiency of the thermoregulation system).
♦ Some diseases ( hypertonic disease, heart failure, endocrinopathies, hyperthyroidism, obesity, vegetovascular dystonia).
♦ Uncoupling of oxidation and phosphorylation processes in cell mitochondria by means of exogenous (2,4-dinitrophenol, dicoumarol, oligomycin, amytal) and endogenous agents (excess of thyroid hormones, catecholamines, progesterone, high fatty acids and mitochondrial uncouplers - thermogenins).
PATHOGENESIS OF HYPERTHERMIA
Under the action of a hyperthermic factor in the body, a triad of emergency adaptive mechanisms is activated: 1) a behavioral response (“avoidance” from the action of the thermal factor); 2) intensification of heat transfer and reduction of heat production; 3) stress. The insufficiency of protective mechanisms is accompanied by overstrain and breakdown of the thermoregulation system with the formation of hyperthermia.
During the development of hyperthermia, two main stages are distinguished: compensation (adaptation) and decompensation (disadaptation) of the mechanisms of thermoregulation of the body. Some authors distinguish the final stage of hyperthermia - hyperthermic coma. Stage of compensation characterized by the activation of emergency mechanisms of adaptation to overheating. These mechanisms are aimed at increasing heat transfer and reducing heat production. Due to this, body temperature remains within the upper limit of the normal range. There is a feeling of heat, dizziness, tinnitus, flashing "flies" and darkening in the eyes. Can develop thermal neurasthenic syndrome, characterized by a drop in efficiency, lethargy, weakness and apathy, drowsiness, physical inactivity, sleep disturbances, irritability, headaches.
Stage of decompensation
The stage of decompensation is characterized by a breakdown and inefficiency of both central and local arrangements thermoregulation, which leads to a violation of the temperature homeostasis of the body. The temperature of the internal environment rises to 41-43 ° C, which is accompanied by changes in the metabolism and functions of organs and their systems.
♦ Sweating is reduced often only scanty sticky sweat is noted; the skin becomes dry and hot. Dry skin is considered an important sign of hyperthermia decompensation.
♦ Increased hypohydration. The body loses a large number of liquids as a result of increased sweating and urination at the stage of compensation, which leads to hypohydration of the body. The loss of 9-10% of the fluid is combined with significant life disorders. This state is referred to as desert sickness syndrome.
♦ Hyperthermic cardiovascular syndrome develops: tachycardia increases, cardiac output decreases, cardiac output is maintained due to increased heart rate, systolic blood pressure may briefly increase, and diastolic blood pressure decreases; microcirculation disorders develop.
♦ Growing signs of exhaustion mechanisms stress and the underlying adrenal and thyroid insufficiency: hypodynamia, muscle weakness, a decrease in myocardial contractility, the development of hypotension, up to collapse are observed.
♦ The rheological properties of blood change: its viscosity increases, signs of sludge syndrome, disseminated intravascular coagulation of blood proteins (DIC) and fibrinolysis appear.
♦ Metabolic and physico-chemical disorders develop: Cl - , K+, Ca 2 +, Na+, Mg 2 + and other ions are lost; water-soluble vitamins are excreted from the body.
♦ Acidosis is registered. In connection with the increase in acidosis, ventilation of the lungs and the release of carbon dioxide increase; increased oxygen consumption; the dissociation of HbO 2 decreases.
♦ Increasing concentration in the blood plasma of the so-called average mass molecules(from 500 to 5,000 Da) - oligosaccharides, polyamines, peptides, nucleotides, glyco- and nucleoproteins. These compounds have high cytotoxicity.
♦ Squirrels appear heat shock.
♦ Significantly modified physical and chemical lipid state. SPOL is activated, the fluidity of membrane lipids increases, which violates the functional properties of membranes.
♦ In the tissues of the brain, liver, lungs, muscles, increased content of lipid peroxidation products- diene conjugates and lipid hydroperoxides.
The state of health at this stage deteriorates sharply, there is increasing weakness, palpitations, throbbing headache, feeling extreme heat and feeling of thirst, mental agitation and restlessness, nausea and vomiting.
Hyperthermia can be accompanied (especially in hyperthermic coma) by edema of the brain and its membranes, death of neurons, myocardial dystrophy, liver, kidneys, venous hyperemia and petechial hemorrhages in the brain, heart, kidneys and other organs. Some patients experience significant neuropsychiatric disorders(delusions, hallucinations).
With hyperthermic coma develops stupor and loss of consciousness; clonic and tetanic convulsions, nystagmus, dilated pupils, followed by their constriction, can be observed.
OUTCOMES
With an unfavorable course of hyperthermia and the absence of medical assistance, the victims die as a result of circulatory failure, cessation of cardiac activity (ventricular fibrillation and asystole) and breathing.
Heatstroke
Heatstroke- acute form hyperthermia with the achievement of life-threatening body temperatures of 42-43 ° C (rectal) for a short time.
Etiology
The action of high intensity heat.
Low efficiency of the mechanisms of adaptation of the body to elevated ambient temperature.
Pathogenesis
Heatstroke - hyperthermia with a short stage of compensation, quickly turning into a stage of decompensation. Body temperature tends to approach the temperature of the environment. Lethality at heat stroke reaches 30%. The death of patients is the result of acute progressive intoxication, heart failure and respiratory arrest.
Body intoxication molecules of average mass is accompanied by hemolysis of erythrocytes, an increase in the permeability of the walls of blood vessels, the development DIC syndrome.
Acute heart failure is the result of acute dystrophic changes in the myocardium, disorders of actomyosin interaction and energy supply cardiomyocytes.
Respiratory arrest may be a consequence of increasing hypoxia of the brain, edema and hemorrhage in the brain.
Sunstroke
Sunstroke- hyperthermic state, caused by the direct impact of solar radiation energy on the body.
Etiology. Cause sunstroke- excessive insolation. The infrared part has the greatest pathogenic effect. solar radiation, i.e. radiation heat. The latter, in contrast to convection and conduction heat, simultaneously warms up the superficial and deep tissues of the body, including brain tissue.
Pathogenesis. The leading link in the pathogenesis is the defeat of the central nervous system.
Initially, arterial hyperemia of the brain develops. This leads to an increase in education interstitial fluid and to compression of the substance of the brain. Compression of the venous vessels and sinuses located in the cranial cavity contributes to the development of venous hyperemia of the brain. In its turn, venous congestion leads to hypoxia, edema and small focal hemorrhages in the brain. As a result, focal symptoms appear in the form of violations of sensitivity, movement and autonomic functions.
Increasing disturbances in metabolism, energy supply and plastic processes in brain neurons potentiate decompensation of thermoregulation mechanisms, dysfunctions of the cardiovascular system, respiration, endocrine glands, blood, other systems and organs.
Sunstroke is fraught with a high probability of death (due to dysfunction of the cardiovascular system and the respiratory system), as well as the development of paralysis, sensory disorders and nervous trophism.
Principles of therapy and prevention of hyperthermic conditions
Treatment of victims is organized taking into account the etiotropic, pathogenetic and symptomatic principles.
Etiotropic treatment aimed at stopping the cause of hyperthermia and eliminating risk factors. For this purpose, methods are used aimed at normalizing heat transfer, stopping the action of high temperature and uncouplers of oxidative phosphorylation.
Pathogenetic therapy aims to block the key mechanisms of hyperthermia and stimulate adaptive processes (compensation, protection, recovery). These goals are achieved through:
Normalization of CCC functions, respiration, blood volume and viscosity, mechanisms of neurohumoral regulation of sweat gland function.
Elimination of shifts in the most important parameters of homeostasis (pH, osmotic and oncotic blood pressure, blood pressure).
Detoxification of the body (hemodilution and stimulation of the excretory function of the kidneys).
Symptomatic treatment in hyperthermic conditions, it is aimed at eliminating unpleasant and painful sensations that aggravate the condition of the victim (“unbearable” headache, increased sensitivity of the skin and mucous membranes to heat, feelings of fear of death and depression); treatment of complications and associated pathological processes.
Prevention of hyperthermic conditions It is aimed at preventing excessive exposure to the body of the thermal factor.
HYPERTHERMAL REACTIONS
Hyperthermic reactions are manifested by a temporary increase in body temperature due to the transient predominance of heat production over heat transfer while maintaining the mechanisms of thermoregulation.
According to the criterion of origin, endogenous, exogenous and combined hyperthermic reactions (malignant hyperthermia) are distinguished. Endogenous hyperthermic reactions subdivided into psychogenic, neurogenic and endocrine.
Psychogenic hyperthermic reactions develop when severe stress and psychopathological conditions.
Neurogenic hyperthermic reactions are divided into centrogenic and reflex.
♦ Centrogenic hyperthermic reactions develop with direct stimulation of the neurons of the thermoregulation center responsible for heat production.
♦ Reflex hyperthermic reactions occur with strong irritation of various organs and tissues: bile ducts of the liver and bile ducts; pelvis of the kidneys and urinary tract during the passage of stones through them.
Endocrine hyperthermic reactions develop as a result of hyperproduction of catecholamines (with pheochromocytoma) or thyroid hormones (with hyperthyroid conditions). The leading mechanism is the activation of exothermic metabolic processes, including the formation of oxidation and phosphorylation uncouplers.
Exogenous hyperthermic reactions divided into medicinal and non-medicinal.
Medicinal (drug, pharmacological) hyperthermic reactions are caused by drugs that have an uncoupling effect.
effect: sympathomimetics (caffeine, ephedrine, dopamine), Ca 2 + - containing drugs.
Non-drug hyperthermic reactions are caused by substances that have a thermogenic effect: 2,4-dinitrophenol, cyanides, amytal. These substances activate the sympathetic-adrenal and thyroid systems.
FEVER
Fever- a typical pathological process characterized by a temporary increase in body temperature due to the dynamic restructuring of the thermoregulation system under the action of pyrogens.
ETIOLOGY
The cause of fever is pyrogen. According to the source of occurrence and mechanism of action, primary and secondary pyrogens are distinguished.
Primary pyrogens
Primary pyrogens themselves do not affect the thermoregulatory center, but cause the expression of genes encoding the synthesis of cytokines (pyrogenic leukokines).
By origin, infectious and non-infectious primary pyrogens are distinguished.
Pyrogens of infectious origin is the most common cause of fever. Infectious pyrogens include lipopolysaccharides, lipoteichoic acid, and exotoxins acting as superantigens.
♦ Lipopolysaccharides(LPS, endotoxins) have the highest pyrogenicity LPS is part of the membranes of microorganisms, mainly gram-negative. The pyrogenic effect is characteristic of lipid A, which is part of LPS.
♦ Lipoteichoic acid. Gram-positive microbes contain lipoteichoic acid and peptidoglycans, which have pyrogenic properties.
By structure, pyrogens of non-infectious origin are more often proteins, fats, less often - nucleic acids or nucleoproteins. These substances can come from outside ( parenteral administration blood components, vaccines, fat emulsions into the body) or be formed in the body itself (with non-infectious inflammation, myocardial infarction, tumor decay, erythrocyte hemolysis, allergic reactions).
secondary pyrogens. Under the influence of primary pyrogens, cytokines (leukokines) are formed in leukocytes, which have pyrogenic activity in a negligible dose. Pyrogenic leukokines are called
are secondary, true, or leukocyte pyrogens. These substances directly affect the thermoregulatory center, changing its functional activity. Pyrogenic cytokines include IL1 (previously referred to as "endogenous pyrogen"), IL6, TNFα, IFN-γ.
FEVER PATHOGENESIS
Fever is a dynamic and phasic process. According to the criterion of changes in body temperature, three stages of fever are distinguished: I- rise in temperature, II- standing temperature on elevated level And III- lowering the temperature to the normal range.
Temperature rise stage
Stage of rise in body temperature (stage I, st. incrementi) It is characterized by the accumulation of an additional amount of heat in the body due to the predominance of heat production over heat transfer.
Pyrogenic leukokines from the blood penetrate the blood-brain barrier and in the preoptic zone of the anterior hypothalamus interact with the receptors of nerve cells of the thermoregulation center. As a result, membrane-bound phospholipase A 2 is activated and arachidonic acid is released.
In the neurons of the thermoregulation center, the activity of cyclooxygenase significantly increases. The result of metabolism arachidonic acid along the cyclooxygenase pathway is an increase in the concentration of PgE 2.
Formation of PgE 2- one of the key links in the development of fever.
The argument for this is the fact that fever is prevented by suppressing the activity of cyclooxygenase with non-steroidal anti-inflammatory drugs (NSAIDs, for example, acetylsalicylic acid or diclofenac).
PgE 2 activates adenylate cyclase, which catalyzes the formation of cyclic 3,5'-adenosine monophosphate (cAMP) in neurons. This, in turn, increases the activity of cAMP-dependent protein kinases, which leads to a decrease in the excitability threshold of cold receptors (i.e., an increase in their sensitivity).
Due to this, the normal blood temperature is perceived as low: the impulsation of cold-sensitive neurons to the effector neurons of the posterior hypothalamus increases significantly. For this reason, the so-called "Set temperature point" the center of thermoregulation increases.
The changes described above are the central link in the mechanism of development of stage I fever. They trigger peripheral mechanisms of thermoregulation.
Heat transfer is reduced as a result of activation of neurons in the nuclei of the sympathetic-adrenal system located in the posterior parts of the hypothalamus.
♦ An increase in sympathetic-adrenal influences leads to a generalized narrowing of the lumen of skin arterioles and subcutaneous tissue, reducing their blood supply, which significantly reduces heat transfer.
♦ A decrease in skin temperature causes an increase in impulses from its cold receptors to the neurons of the thermoregulation center, as well as to the reticular formation.
Activation of heat production mechanisms (contractile and non-contractile thermogenesis).
♦ Activation of the structures of the reticular formation stimulates contractile muscle thermogenesis processes in connection with the excitation of γ- and α-motor neurons of the spinal cord. A thermoregulatory myotonic state develops - tonic tension of the skeletal muscles, which is accompanied by an increase in heat production in the muscles.
♦ The increasing efferent impulsation of the neurons of the posterior hypothalamus and the reticular formation of the brain stem causes the synchronization of contractions of individual muscle bundles of the skeletal muscles, which manifests itself as muscle trembling.
♦ Non-shivering (metabolic) thermogenesis- another important mechanism of heat production in fever. Its causes: activation of sympathetic influences on metabolic processes and an increase in the level of thyroid hormones in the blood.
The increase in temperature is due to the simultaneous increase in heat production and the limitation of heat transfer, although the significance of each of these components may be different. In stage I fever, an increase in basal metabolic rate increases body temperature by 10-20%, and the rest is the result of a decrease in skin heat transfer due to vasoconstriction.
The ambient temperature has a relatively small effect on the development of fever and the dynamics of body temperature. Consequently, with the development of fever, the thermoregulation system does not get upset, but dynamically rebuilds and works on a new functional level. This distinguishes fever from all other hyperthermic conditions.
The stage of standing body temperature at an elevated level
Stage of standing body temperature at an elevated level (stage II, st. fastigii) characterized by a relative balance of heat production and heat transfer at a level significantly exceeding the pre-fever.
Thermal balance established through the following mechanisms:
♦ increased activity of heat receptors in the preoptic zone of the anterior hypothalamus, caused by elevated temperature blood;
♦ temperature activation of peripheral thermosensors internal organs helps to establish a balance between adrenergic influences and increasing cholinergic effects;
♦ increased heat transfer is achieved by expanding the arterioles of the skin and subcutaneous tissue and increased sweating;
♦ decrease in heat production occurs due to a decrease in the intensity of metabolism.
The totality of daily and stage dynamics in fever is denoted as temperature curve. There are several typical types of temperature curve.
♦ Constant. With it, the daily range of fluctuations in body temperature does not exceed 1 ° C. This type of curve is often found in patients with lobar pneumonia or typhoid fever.
♦ Remitting. Characterized by daily fluctuations in temperature of more than 1 °C, but without a return to the normal range (often observed at viral diseases).
♦ laxative, or intermittent. Fluctuations in body temperature during the day reach 1-2 ° C, and it can return to normal for several hours, followed by its increase. This type of temperature curve is often recorded with abscesses of the lungs, liver, purulent infection, tuberculosis.
♦ exhausting, or hectic. It is characterized by repeated rises in temperature during the day by more than 2-3 ° C with its rapid subsequent declines. This pattern is often observed in sepsis.
There are also some other types of temperature curves. Given that the temperature curve in infectious fever to a large extent depends on the characteristics of the microorganism, determining its type can be of diagnostic value.
During fever, several degrees of increase in body temperature:
♦ weak, or subfebrile (in the range of 37-38 °C);
♦ moderate, or febrile (38-39 °C);
♦ high, or pyretic (39-41 °C);
♦ excessive, or hyperpyretic (above 41 °C).
The stage of decreasing body temperature to normal
The stage of lowering the body temperature to the values of the normal range (stage III fever, st. decrementi) characterized by a gradual decrease in the production of leukokines.
Cause: the termination of the action of the primary pyrogen due to the destruction of microorganisms or non-infectious pyrogenic substances.
Consequences: the content of leukokines and their influence on the thermoregulatory center decrease, as a result of which the “setting temperature point” decreases.
Varieties of temperature reduction at stage III fever:
♦ gradual decline, or lytic(more often);
♦ rapid decline, or critical(less often).
METABOLISM IN FEVER
The development of fever is accompanied by a number of metabolic changes.
BX at stages I and II, fever increases due to the activation of the sympathetic-adrenal system, the release of iodine-containing thyroid hormones into the blood, and thermal stimulation of metabolism. This provides energy and metabolic substrates for the increased functioning of a number of organs and contributes to an increase in body temperature. At stage III fever, the basal metabolic rate decreases.
carbohydrate metabolism It is characterized by a significant activation of glycogenolysis and glycolysis, but (due to the action of uncouplers) it is combined with its low energy efficiency. This greatly stimulates the breakdown of lipids.
Fat metabolism with fever, it is characterized by a predominance of catabolic processes, especially with prolonged stage II. In fever, lipid oxidation is blocked at the stages of intermediate products, mainly CT, which contributes to the development of acidosis. For the prevention of these disorders with long-term feverish conditions patients should consume large amounts of carbohydrates.
Protein metabolism in acute moderate fever with an increase in temperature up to 39 ° C, it is not significantly upset. The prolonged course of fever, especially with a significant increase in body temperature, leads to disruption of plastic processes, the development of dystrophies in various bodies and exacerbate disorders of the body as a whole.
Water-electrolyte exchange subject to significant changes.
♦ Stage I increases fluid loss due to increased sweat and urine production, accompanied by loss of Na+, Ca 2+, Cl - .
♦ Stage II activates the release of corticosteroids from the adrenal glands (including aldosterone) and ADH from the pituitary gland. These hormones activate the reabsorption of water and salts in the tubules of the kidneys.
♦ At stage III, the content of aldosterone and ADH decreases, the water and electrolyte balance normalizes.
Signs of renal, hepatic or heart failure, various endocrinopathies, malabsorption syndromes appear with fever with significant damage to the relevant organs.
FUNCTIONS OF ORGANS AND THEIR SYSTEMS IN FEVER
With fever, the functions of organs and physiological systems change. Causes:
♦ impact on the body of the primary pyrogenic agent;
♦ fluctuations in body temperature;
♦ the influence of the body's regulatory systems;
♦ involvement of organs in the implementation of various thermoregulatory reactions.
Consequently, this or that deviation of the functions of organs during fever is their integrative reaction to the above factors.
Manifestations
Nervous system
♦ Nonspecific neuropsychiatric disorders: irritability, poor sleep, drowsiness, headache; confusion, lethargy, sometimes hallucinations.
♦ Hypersensitivity skin and mucous membranes.
♦ Violation of reflexes.
♦ Change pain sensitivity, neuropathy.
Endocrine system
♦ Activation of the hypothalamic-pituitary complex leads to an increase in the synthesis of individual liberins, as well as ADH in the hypothalamus.
♦ Increased production of ACTH and TSH in the adenohypophysis.
♦ Increase in blood levels of corticosteroids, catecholamines, T 3 and T 4 , insulin.
♦ Changes in the content of tissue (local) biologically active substances - Pg, leukotrienes, kinins and others.
♦ Tachycardia. The degree of increase in heart rate is directly proportional to the increase in body temperature.
♦ Often - arrhythmias, hypertensive reactions, centralization of blood flow.
external respiration
♦ Normally, as body temperature rises, ventilation increases. The main stimulants of respiration are an increase in pCO 2 and a decrease in blood pH.
♦ The frequency and depth of breaths change in different ways: unidirectional or multidirectional, ie. an increase in the depth of breathing can be combined with a decrease in its frequency and vice versa.
Digestion
♦ Decreased appetite.
♦ Decreased salivation, secretory and motor function(the result of activation of the sympathetic-adrenal system, intoxication and elevated body temperature).
♦ Suppression of education digestive enzymes pancreas and bile by the liver.
Kidneys. The revealed changes reflect only the restructuring of various regulatory mechanisms and functions of other organs and systems during fever.
THE SIGNIFICANCE OF FEVER
Fever is an adaptive process, but under certain conditions it can be accompanied by pathogenic effects.
Adaptive effects of fever
♦ Direct bacteriostatic and bactericidal effects: coagulation of foreign proteins and reduction of microbial activity.
♦ Indirect effects: potentiation of specific and non-specific factors of the IBN system, initiation of stress.
Pathogenic effects of fever
♦ The direct damaging effect of high temperature consists in the coagulation of its own proteins, disruption of electrogenesis, and an increase in FOL.
♦ Indirect damaging effect: functional overload of organs and their systems can lead to the development of pathological reactions.
DIFFERENCES FROM OTHER HYPERTHERMIC CONDITIONS
Hyperthermia is caused by high ambient temperature, impaired heat transfer and heat production, and the cause of fever is pyrogens.
When the body overheats, a violation of the mechanisms of thermoregulation occurs, with hyperthermic reactions - an inappropriate increase in heat production, and with fever, the thermoregulation system is adaptively rebuilt.
With overheating, the body temperature rises passively, and with a fever, it rises actively, at a cost. significant amount energy.
PRINCIPLES AND METHODS OF THE TREATMENT OF FEVER
It must be remembered that a moderate increase in body temperature during fever has an adaptive value, consisting in the activation of a complex of protective, adaptive and compensatory reactions aimed at destroying or weakening pathogenic agents. Conducting antipyretic therapy is advisable only when there is or possibly a damaging effect of hyperthermia on the vital activity of the body:
♦ with excessive (more than 38.5 °C) increase in body temperature;
♦ in patients with decompensated diabetes or circulatory failure;
♦ in newborns, children infancy and the elderly due to the imperfection of the body's thermoregulation system.
Etiotropic treatment aimed at stopping the action of the pyrogenic agent.
In infectious fever, antimicrobial therapy is carried out.
With a fever of non-infectious origin, measures are taken to stop the ingestion of pyrogenic substances (whole blood or plasma, vaccines, sera, protein-containing substances) into the body; removal from the body of a source of pyrogenic agents (for example, necrotic tissue, tumor, abscess contents).
Pathogenetic therapy aims to block the key links of pathogenesis and, as a result, to reduce excessively high body temperature. This is achieved:
Inhibition of production, prevention or reduction of the effects of substances formed in the neurons of the thermoregulation center under the influence of leukokines: PgE, cAMP. For this, cyclooxygenase inhibitors are used - acetylsalicylic acid and others.
Blockade of the synthesis and effects of leukocyte pyrogens (IL1, IL6, TNF, γ-IFN).
Reducing excess heat production by suppressing the intensity of oxidative reactions. The latter can be achieved, for example, by using quinine preparations.
Symptomatic treatment aims to eliminate painful and unpleasant sensations and conditions that aggravate the patient's status. At
fever, such symptoms include severe headache, nausea and vomiting, pain in the joints and muscles ("breaking"), cardiac arrhythmias.
pyrotherapy
Artificial hyperthermia (pyrotherapy) has been used in medicine since ancient times. Currently, therapeutic pyrotherapy is used in combination with other medical and non-drug treatments. There are general and local pyrotherapy. General pyrotherapy. General pyrotherapy is carried out by reproducing fever with purified pyrogens (for example, pyrogenal or substances that stimulate the synthesis of endogenous pyrogens). A moderate increase in body temperature stimulates adaptive processes in the body:
♦ specific and non-specific mechanisms of the IBN system (in some infectious processes - syphilis, gonorrhea, post-infectious arthritis);
♦ plastic and reparative processes in bones, tissues and parenchymal organs (during their destruction, damage, degeneration, after surgical interventions).
local hyperthermia. local hyperthermia perse, as well as in combination with other methods of treatment, reproduce to stimulate regional defense mechanisms (immune and non-immune), repair and blood circulation. Regional hyperthermia is induced in chronic inflammatory processes, erosions and ulcers of the skin, subcutaneous tissue, as well as in certain types of malignant neoplasms.
HYPOTHERMAL CONDITIONS
Hypothermic states are characterized by a decrease in body temperature below normal. Their development is based on the breakdown of thermoregulation mechanisms that ensure the optimal thermal regime of the body. There are cooling of the body (actually hypothermia) and controlled (artificial) hypothermia, or medical hibernation.
Hypothermia
Hypothermia- a typical form of a heat exchange disorder - occurs as a result of the effect on the body of a low temperature of the external environment and a significant decrease in heat production. Hypothermia is characterized by a violation (disruption) of the mechanisms of thermoregulation and is manifested by a decrease in body temperature below normal.
ETIOLOGY
Reasons for development body cooling are diverse.
♦ Low ambient temperature is the most common cause of hypothermia. The development of hypothermia is possible not only at negative (below 0 °C), but also at positive external temperatures. It has been shown that a decrease in body temperature (in the rectum) to 25 ° C is already life-threatening; up to 17-18 ° C - usually fatal.
♦ Extensive paralysis of muscles or a decrease in their mass (for example, with their malnutrition or dystrophy).
♦ Disturbance of a metabolism and decrease in efficiency of exothermic processes of a metabolism. Such conditions can develop with adrenal insufficiency, leading to a deficiency in the body of catecholamines; with severe hypothyroid conditions; with injuries and dystrophic processes in the centers of the sympathetic nervous system.
♦ The extreme degree of exhaustion of the body.
Risk factors body cooling.
♦ Increased air humidity.
♦ High air speed (strong wind).
♦ Excessive dampness or wetness of clothing.
♦ Cold water exposure. Water is about 4 times more heat-consuming and 25 times more thermally conductive than air. In this regard, freezing in water can occur when relatively high temperature: at a water temperature of +15 ° C, a person remains viable for no more than 6 hours, at +1 ° C - about 0.5 hours.
♦ Prolonged fasting, physical fatigue, alcohol intoxication, as well as various diseases, injuries and extreme conditions.
PATHOGENESIS OF HYPOTHERMIA
The development of hypothermia is a staged process. Its formation is based on a more or less prolonged overvoltage and, in the end, the breakdown of the body's thermoregulation mechanisms. In this regard, in hypothermia (as in hyperthermia), two stages of its development are distinguished: compensation (adaptation) and decompensation (disadaptation).
Stage of compensation
The compensation stage is characterized by the activation of emergency adaptive reactions aimed at reducing heat transfer and increasing heat production.
♦ Changing the individual's behavior (directed withdrawal from a cold room, use of warm clothes, heaters, etc.).
♦ Reduced heat transfer (achieved due to the reduction and cessation of sweating, narrowing of the arterial vessels of the skin and subcutaneous tissues).
♦ Activation of heat production (by increasing blood flow in the internal organs and increasing muscle contractile thermogenesis).
♦ Inclusion of a stress reaction (an excited state of the victim, an increase in the electrical activity of thermoregulation centers, an increase in the secretion of liberins in hypothalamic neurons, in pituitary adenocytes - ACTH and TSH, in the adrenal medulla - catecholamines, and in their cortex - corticosteroids, in the thyroid gland - thyroid hormones ).
Thanks to the complex these changes body temperature, although it decreases, but still does not go beyond lower bound norms. If the causative factor continues to act, then compensatory reactions may become insufficient. At the same time, the temperature of not only integumentary tissues decreases, but also internal organs, including the brain. The latter leads to disorders of the central mechanisms of thermoregulation, discoordination and inefficiency of heat production processes - their decompensation develops.
Stage of decompensation
The stage of decompensation (disadaptation) is the result of a breakdown of the central mechanisms of thermoregulation. At the stage of decompensation, body temperature drops below normal level(in the rectum, it drops to 35 ° C and below). Temperature homeostasis of the body is disturbed: the body becomes poikilothermic. Quite often, vicious circles are formed that potentiate the development of hypothermia and disorders of the body's vital functions.
metabolic vicious circle. A decrease in tissue temperature in combination with hypoxia inhibits the course of metabolic reactions. The suppression of the intensity of metabolism is accompanied by a decrease in the release of free energy in the form of heat. As a result, the body temperature drops even more, which additionally suppresses the intensity of metabolism, etc.
Vascular vicious circle. The increasing decrease in body temperature during cooling is accompanied by the expansion of arterial vessels (according to the neuromyoparalytic mechanism) of the skin, mucous membranes, and subcutaneous tissue. The expansion of skin vessels and the influx of warm blood to them from organs and tissues accelerates the process of heat loss by the body. As a result, the body temperature drops even more, blood vessels expand even more, and so on.
neuromuscular vicious circle. Progressive hypothermia causes a decrease in the excitability of nerve centers, including those that control muscle tone and contraction. As a result, such a powerful mechanism of heat production as muscle contractile thermogenesis is turned off. As a result, the body temperature is intensively reduced, which further suppresses neuromuscular excitability, etc.
The deepening of hypothermia causes inhibition of functions, first of the cortical, and subsequently of the subcortical nerve centers. Physical inactivity, apathy and drowsiness develop, which can culminate in coma. In this regard, the stage of hypothermic "sleep" or coma is often distinguished.
With an increase in the action of the cooling factor, freezing and death of the body occurs.
PRINCIPLES OF THE TREATMENT OF HYPOTHERMIA
Treatment of hypothermia depends on the degree of decrease in body temperature and the severity of vital disorders of the body. stage of compensation. At the compensation stage, victims mainly need to stop external cooling and warm the body (in a warm bath, heating pads, dry warm clothes, warm drinks).
Stage of decompensation
At the stage of decompensation of hypothermia, intensive comprehensive medical care is necessary. It is based on three principles: etiotropic, pathogenetic and symptomatic.
Etiotropic treatment includes the following activities.
♦ Measures to stop the effect of the cooling factor and warm the body. Active warming of the body is stopped at a temperature in the rectum of 33-34 ° C in order to avoid the development of a hyperthermic state. The latter is quite probable, since the adequate function of the body's thermoregulation system has not yet been restored in the victim.
♦ Warming the internal organs and tissues (through the rectum, stomach, lungs) gives a greater effect.
pathogenic treatment.
♦ Recovery effective blood circulation and breathing. If breathing is disturbed, release Airways(from mucus, sunken tongue) and carry out mechanical ventilation with air or gas mixtures with high content oxygen. If the activity of the heart is disturbed, then it is performed indirect massage and, if necessary, defibrillation.
♦ Correction of acid-base balance, balance of ions and liquid. For this purpose, balanced salt and buffer solutions (for example, sodium bicarbonate), colloidal solutions of dextran are used.
♦ The elimination of glucose deficiency in the body is achieved by introducing its solutions of different concentrations in combination with insulin, as well as vitamins.
♦ For blood loss, blood, plasma and plasma substitutes are transfused. Symptomatic treatment aimed at eliminating changes
in the body, exacerbating the condition of the victim.
♦ Apply agents that prevent swelling of the brain, lungs and other organs.
♦ Eliminate arterial hypotension.
♦ Normalize diuresis.
♦ Eliminate severe headache.
♦ In the presence of frostbite, complications and concomitant diseases, they are treated.
PRINCIPLES FOR THE PREVENTION OF HYPOTHERMIA
Prevention of body cooling includes a set of measures.
♦ Use of dry warm clothes and shoes.
♦ Proper organization work and rest in the cold season.
♦ Organization of heating points, provision of hot meals.
♦ Medical supervision of participants in winter military operations, exercises, sports competitions.
♦ Prohibition of alcohol intake before a long stay in the cold.
♦ Hardening of the body and acclimatization of a person to environmental conditions.
medical hibernation
Controlled hypothermia(medical hibernation) - a method of controlled decrease in body temperature or part of it in order to reduce the metabolic rate and functional activity of tissues, organs and their systems, as well as increase their resistance to hypoxia.
Controlled (artificial) hypothermia is used in medicine in two varieties: general and local.
TOTAL MANAGED HYPOTHERMIA
Application area. Performing surgical operations in conditions of a significant decrease or even temporary cessation
regional circulation. This was called operations on "dry" organs: heart, brain and some others. Advantages. A significant increase in the stability and survival of cells and tissues under hypoxic conditions at low temperatures. This makes it possible to disconnect the organ from the blood supply for several minutes, followed by the restoration of its vital activity and adequate functioning.
Temperature range. Hypothermia is usually used with a decrease in rectal temperature to 30-28 ° C. If long-term manipulations are necessary, a deeper hypothermia is created using a heart-lung machine, muscle relaxants, metabolic inhibitors, and other influences.
LOCAL CONTROLLED HYPOTHERMIA
local controlled hypothermia individual bodies or tissues (brain, kidneys, stomach, liver, prostate, etc.) are used if necessary for surgical interventions or other therapeutic manipulations on them: correction of blood flow, plastic processes, metabolism, drug efficiency.
Hypothermia occurs when heat transfer exceeds heat production, and the body loses heat. This usually occurs when the temperature drops significantly. human environment environment, which is exacerbated by the lack of warm clothing, strong wind as well as factors such as alcohol intake. In the latter case, due to a sharp expansion of the skin vessels, a misleading impression of warmth is created, while heat losses increase sharply.
As with overheating, the development of hypothermia differs three stages.
1. compensation stage, consisting in an increase in heat production (increased muscle activity, intensification of metabolic processes) and a decrease in heat transfer (spasm peripheral vessels, respiratory depression, bradycardia).
2. decompensation stage, which is characterized by a “breakdown” and a perversion of thermoregulatory mechanisms (expansion of skin vessels, tachypnea, tachycardia, etc.), as a result of which a homoiothermic organism acquires the features of a poikilothermic one.
3. Coma stage, during the onset of which a state of "cold anesthesia" develops: blood pressure drops, breathing acquires the features of a periodic one, and the level of metabolic processes decreases sharply. Death usually occurs as a result of paralysis of the respiratory center.
With deep hypothermia due to sharp decline the level of metabolic processes significantly decreases the need for oxygen in tissues. This feature led to the creation of a method of artificial hypothermia, which is now mandatory in the arsenal of surgeons and resuscitators.
The most sensitive organ to hypoxia (oxygen starvation) is the brain. As a result of a violation of the oxygen supply to nerve cells, the processes of oxidative phosphorylation are inhibited in them, as a result of which the level of high-energy phosphorus compounds in the brain tissue progressively decreases: phosphocreatine, adenosine triphosphate. At the same time, the amount of adenosine diphosphate, adenosine monophosphate and inorganic phosphorus increases. The period of exhaustion of the energy reserves of the brain under conditions of deep hypoxia, according to various researchers, ranges from two to five minutes; by the thirty-fifth minute of brain hypoxia under normothermic conditions, generalized damage to the membranes of nerve cells occurs. As a rule, when the body is removed from the state of clinical death 7-10 minutes after its onset, although life is restored, however, brain damage may already be irreversible and mental activity the resuscitated person is also broken irreversibly. In surgical practice, sometimes it is necessary to operate on a "dry" heart, that is, free from blood (for example, with plastic surgery about congenital malformations), and circulatory arrest in this case should sometimes last several tens of minutes. The use of a heart-lung machine in this case is fraught with serious complications associated primarily with the fact that with prolonged blood circulation through this apparatus, generalized damage to erythrocyte membranes can occur. Under conditions of hypothermia, the resistance of nerve cells to the hypoxic factor increases significantly, which increases the possibility of a full recovery of the human psyche even after long period clinical death and opens up great opportunities in cardiac surgery, allowing long time operate under conditions of circulatory arrest. For this purpose, it is applied artificial hypothermia, the founder of the doctrine of which is the French scientist Labori.
Artificial hypothermia can be physical and chemical. Most often, these two types of hypothermia are used in combination.
Physical hypothermia is achieved by cooling the patient's body from the outside: wrapping it with ice containers. When using a heart-lung machine, the blood circulating in it is cooled to 25-28°C.
Chemical hypothermia caused by the introduction to the patient of various chemical substances And medicines, acting on thermoregulatory mechanisms and allowing to shift the body's heat balance towards heat loss.
Can be distinguished four groups such medicinal effects.
1. adrenolytic drugs. Skin vessels narrow under the influence of adrenergic influences, so the interruption of sympathetic effects on vascular tone leads to the expansion of peripheral vessels and increased heat loss by the body.
2. Muscle relaxants. These substances disrupt the transmission of a nerve impulse to the muscle at the level of the neuromuscular synapse and lead to immobilization, as a result of which heat production in the muscles decreases and heat transfer begins to prevail over heat production. (Naturally, if there are no conditions for the development of malignant hyperthermia when using muscle relaxants).
3. Antagonists of thyroid hormones. Thyroid hormones have the effect of uncoupling respiration and phosphorylation, and thus reduce the formation of ATP. However, this uncoupling leads to the stimulation of free oxidation processes, that is, to an increase in heat generation. Blockade this mechanism medication also leads to the predominance of heat transfer over heat production.
4. Medications that affect the centers of thermoregulation. This group of drugs includes primarily general anesthesia, and in addition, neurotropic drugs acting on the hypothalamic centers. The optimal selection of drugs that inhibit the central regulation of heat production and stimulate centers that enhance heat transfer can give a pronounced effect of heat loss by the body.
Labori called the loss of heat in the body thermolysis, and a complex of drugs leading to the achievement of a hypothermic effect - lytic cocktail.
By combining physical and chemical methods hypothermia, you can lower the body temperature to 16-18 ° C, significantly reduce the brain's need for oxygen and dramatically increase its resistance to hypoxia.
In surgical and resuscitation practice, it is also successfully used local hypothermia of the head with the help of a special helmet worn on the head, pierced with tubes through which coolant circulates. This reduces the temperature of the brain and thereby increases the resistance of nerve cells to hypoxia and at the same time leaves the patient's body free from cooling systems, which facilitates surgical and resuscitation procedures.
The method of cooling the blood passed through a special apparatus is also used, which leads to the rapid achievement of a state of deep hypothermia of the internal organs and allows, for example, during heart operations, not to resort to a heart-lung machine.
A very important and still not fully resolved problem is the withdrawal of the body from the state of artificial hypothermia. If this state is deep enough and continues for a relatively long time, significant changes occur in the body in almost all types of metabolism. Their normalization in the process of removing the body from hypothermia is an important aspect of the application of this method in medicine.
1. Definition of hypothermia.
2. Etiology.
3. Pathogenesis of hypothermia.
4. Collapse.
1. Definition of hypothermia.
Hypothermia is an abnormal decrease in the body temperature of an animal, which is a relatively rare phenomenon. A decrease in body temperature has not only diagnostic, but also prognostic value.
When evaluating hypothermia, care must be taken to be aware of possible technical errors in temperature measurement. Incomplete closure of the anus, immersion of the thermometer in fecal matter, its deterioration may be the reason that the mercury column has not risen to the appropriate height. In this case, it is necessary to measure the temperature again, observing all the rules of thermometry.
Temperature 1° below normal is called subnormal. A persistent decrease in temperature, sometimes with a tendency to further fall, occurs in horses in severe cases of infectious encephalomyelitis, with maternity paresis in cattle, and diffuse myelitis in dogs.
Subnormal temperatures are also observed at low external temperatures in old, emaciated horses, with injuries and brain tumors, after heavy blood loss, with circulatory disorders, some autointoxications (uremia, diabetic coma), under the influence of drugs and antipyretics. With improvement general condition the patient, strengthening his nutrition and increasing nervous tone, the temperature rises to normal.
The temperature decreases most sharply during the collapse. A fall of 2° below the norm is called a moderate collapse, and a fall of 3 or 4° is called an algid collapse. The collapse differs from the crisis not only by severe hypothermia, but also by cooling of the entire surface of the body, a decline in cardiac activity, and general weakness. The skin during collapse is cold to the touch, covered with sticky sweat; mucous membranes are cyapotic; eyes sunk deep; the lower lip hangs down; legs tremble and bend at the joints; pulse quickened, weak, barely perceptible. In a crisis, simultaneously with a decrease in body temperature, the heartbeat slows down; during collapse, the body temperature drops, a. the heart impulse, on the contrary, becomes more and more frequent. The most typical picture of collapse can be observed with rupture of the stomach and intestines in horses, ruptures of the uterus and vagina in cattle, and feed poisoning.
2. Etiology
Causes development of body cooling are diverse.
1. Low ambient temperature (water, air, surrounding objects, etc.) is the most common cause of hypothermia. It is important that the development of hypothermia is possible not only at negative (below 0 °C), but also at positive external temperatures. It has been shown that a decrease in body temperature (in the rectum) to 25 °C is already life-threatening, to 20 °C, as a rule, is irreversible, to 17-18 °C is usually fatal.
The statistics of mortality from cooling is indicative. Hypothermia and human death during cooling is observed at air temperatures from +10 °C to 0 °C in about 18%; from 0 °С to -4 °С in 31%; from -5 °С to -12 °С in 30%; from -13 °С to -25 °С in 17%; from -26 °С to -43 °С in 4%. It can be seen that the maximum mortality rate during hypothermia is in the air temperature range from +10 °C to -12 °C. Consequently, a person in the conditions of existence on Earth is constantly in the potential danger of cooling.
2. Extensive muscle paralysis and a decrease in their mass (for example, with their malnutrition or dystrophy). This can be caused by trauma or destruction (for example, postischemic, as a result of syringomyelia or other pathological processes) of the spinal cord, damage to the nerve trunks that innervate the striated muscles, as well as some other factors (for example, Ca 2+ deficiency in muscles, muscle relaxants).
3. Metabolic disorders and/or decrease in the efficiency of exothermic metabolic processes. Such conditions most often develop with adrenal insufficiency, leading (among other changes) to a deficiency in the body of catecholamines, with severe hypothyroid conditions, with injuries and dystrophic processes in the centers of the sympathetic nervous system of the hypothalamus.
4. The extreme degree of exhaustion of the body.
In the last three cases, hypothermia develops under the condition of a low external temperature.