Disorder of thermoregulation: causes, symptoms, diagnosis, treatment

Thermoregulation disorders are manifested by hyperthermia, hypothermia, chill-like hyperkinesis, and “chills” syndrome.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]

Pathogenesis of thermoregulation disorders

Regulation of body temperature in warm-blooded animals, i.e. maintaining thermohomeostasis regardless of the ambient temperature, is an achievement of evolutionary development. Body temperature reflects the intensity of bioenergetic processes and is the result of heat production and heat transfer. There are two main phases of thermoregulation - chemical and physical. Chemical thermoregulation is carried out due to local and general metabolism, which contributes to an increase in heat production. Physical thermoregulation ensures heat transfer processes by heat conduction (convection) and heat radiation (radiation), as well as by evaporation of water from the surface of the skin and mucous membranes. The main role in this is played by sweating and vasomotor mechanisms. There are central and peripheral thermosensitive systems. Peripheral thermoregulation includes nerve receptors of the skin, subcutaneous fat and internal organs. The skin is a heat exchange organ and a regulator of body temperature. Hemodynamics plays a significant role. It is one of the mechanisms for maintaining the body's optimal temperature for metabolism. Information about temperature changes is transmitted via afferent systems to the central nervous system. Numerous studies, beginning with the work of Claude Strongernard in the 1880s, have confirmed the special role of the hypothalamus in thermoregulation processes.

The hypothalamus is divided into the medial preoptic area of the anterior hypothalamus (MPA), which plays the role of the "heat center" or heat transfer center, and the posterior hypothalamus - the "cold center" or heat production center, which includes the ventro- and dorsomedial nuclei of the hypothalamus. Thermosensitive neurons of the MPA and posterior hypothalamus are sensitive to both central and peripheral temperature changes. Thermosensitive centers of the brain also include the mesencephalic activating system, the hippocampus, the amygdala nuclei, and the cerebral cortex. The spinal cord contains specific thermosensitive elements.

There are several theories explaining the maintenance of body temperature. The most common is the "set point" theory. The "set point" is the temperature level at which the activity of thermoregulatory mechanisms is minimal, tends to zero, and is optimal under given conditions. Disturbing effects that change the body's temperature regime lead to the activation of either heat production or heat transfer processes, which returns the temperature to the initial "set point". Studies devoted to thermoregulation issues reflect the involvement of the sympathetic and parasympathetic systems.

Numerous studies have been devoted to the influence of pharmacological drugs on vegetative functions, including thermoregulation. It has been established that alpha and beta-adrenergic blockers lead to a decrease in body temperature due to an increase in skin blood flow, which changes the activity of peripheral thermoreceptors. General and local anesthetics, barbiturates, tranquilizers, neuroleptics, ganglionic blockers, acetylcholine and other substances also affect changes in body temperature. At the same time, there is information about their effect on tissue metabolism, skin vascular tone, sweating, myoneural synapse (curare-like agents), muscle tone (cold shivering), but not on thermoreceptors.

The significance of the stem adrenoreceptor and serotonergic systems for thermoregulation and the dependence of temperature on the balance of norepinephrine and serotonin in the hypothalamus are shown. Much attention is paid to the ratio of the concentration of sodium and calcium ions in the extracellular fluid. Thus, temperature homeostasis is the result of the integrative activity of physiological systems that ensure metabolic processes that are under the coordinating influence of the nervous system.

Non-infectious fever was considered a manifestation of vegetoneurosis, vegetative dystonia, vasomotor neurosis; an abnormal temperature reaction of “vegetative-stigmatized” subjects under the influence of common factors or psychogenic fever in people with certain constitutional features of the nervous system.

The main causes of prolonged subfebrile temperature, "unclear" temperature increases are physiological, psychogenic, neuroendocrine disorders, false causes. Physiological disorders of thermoregulation include an increase in temperature (to subfebrile numbers) of a constitutional (correct) nature, as a result of physical and sports overloads, in some cases in the second half of the menstrual cycle, rarely during the first 3-4 months of pregnancy, which is associated with the activity of the corpus luteum. False temperature depends on a malfunction of the thermometer or simulation. An increase in temperature (up to 40-42 ° C) is often described during hysterical seizures. The temperature curve is characterized by a very rapid rise and a critical drop to a normal, subfebrile or hypofebrile level. Subfebrile temperature in neuroses is found in a third of patients. Psychogenic increase in temperature is observed mainly in childhood and adolescence against the background of vegetative-endocrine disorders of the pubertal period. In these cases, the provoking, triggering factor may be emotions, physical overexertion, stressful situations. A favorable background is allergization, endocrine dysregulation, etc. A conditioned reflex increase in temperature is possible, when the environment itself, for example, temperature measurement, serves as a conditioned stimulus.

Thermoregulation disorders are described by many in hypothalamic syndrome and are even considered as its obligatory sign. 10-30% of all patients with prolonged subfebrile temperature have neuroendocrine-metabolic manifestations of hypothalamic syndrome.

The occurrence of temperature disorders, in particular hyperthermia, as shown by the data of clinical and electrophysiological research, indicates a certain inadequacy of hypothalamic mechanisms. A long-term neurotic syndrome (this is typical for the syndrome of vegetative dystonia) in turn contributes to the deepening and consolidation of the anomaly of temperature reactions.

Diagnosis of thermoregulatory disorders is still difficult and requires a step-by-step approach. It should begin with an epidemiological analysis, a full analysis of the disease, a somatic examination, standard laboratory tests and, in some cases, the use of special methods to exclude a pathological condition that leads to an increase in body temperature. In this case, infectious diseases, tumors, immunological diseases, systemic diseases of connective tissue, demyelinating processes, intoxications, etc. should be excluded first.

Hyperthermia

Hyperthermia can be permanent, paroxysmal, or permanent-paroxysmal.

Permanent hyperthermia is represented by prolonged sub- or febrile temperature. Prolonged subfebrile temperature, or a temperature increase of non-infectious genesis, means its fluctuation within 37-38 °C (i.e. above the individual norm) for more than 2-3 weeks. Periods of elevated temperature can last for several years. In the anamnesis of such patients, high fever during infections and prolonged temperature "tails" are often noted even before the onset of temperature disorders. In most patients, even without treatment, the temperature can normalize in the summer or during the holiday period, regardless of the season. The temperature rises in children and adolescents when attending classes at educational institutions, before a control survey and tests. In students, subfebrile temperature appears or resumes from the 9th-10th day of school.

Characterized by relatively satisfactory tolerance of prolonged and high temperature with preservation of motor and intellectual activity. Some patients complain of weakness, fatigue, headache. Temperature, compared to its increase in healthy people against the background of infection, does not change in the circadian rhythm. It can be monotonous during the day or inverted (higher in the first half of the day). With the amidopyrine test, there is no decrease in temperature; pathological conditions that can cause an increase in body temperature (infections, tumor, immunological, collagen and other processes) are excluded.

Currently, such temperature disorders are considered as manifestations of cerebral vegetative disorders and are included in the picture of vegetative dystonia syndrome, which is interpreted as a psychovegetative syndrome. It is known that the syndrome of vegetative dysfunction can develop against the background of clinical signs of constitutionally acquired hypothalamic dysfunction and without it. At the same time, no difference is found in the frequency of hyperthermic disorders. However, with hyperthermia that has arisen against the background of hypothalamic syndrome, monotonous subfebrile temperature is more common, which is combined with neurometabolic-endocrine disorders, vegetative disorders of both permanent and paroxysmal (vegetative crises) nature. In the syndrome of vegetative dystonia, accompanied by a disorder of thermoregulation without clinical signs of hypothalamic dysfunction, hyperthermia is characterized by febrile numbers, which can be of a long-term persistent nature.

Paroxysmal hyperthermia is a temperature crisis. The crisis is manifested by a sudden increase in temperature to 39-41 °C, accompanied by chill-like hyperkinesis, a feeling of internal tension, headache, facial flushing and other vegetative symptoms. The temperature lasts for several hours and then falls lytically. After its decrease, weakness and fatigue remain, passing after some time. Hyperthermic crises can occur both against the background of normal body temperature and against the background of long-lasting subfebrile temperature (permanent paroxysmal hyperthermic disorders). A paroxysmal sharp increase in temperature can occur in isolation.

An objective examination of patients showed that signs of dysraphic status and allergic reactions in the anamnesis are significantly more common with hyperthermia than with autonomic dysfunction syndrome without hyperthermic disorders.

In patients with thermoregulation disorders, features were also found in the manifestations of psychovegetative syndrome, consisting in the predominance of depressive-hypochondriac features in combination with introversion and lower indicators of the anxiety level compared to these indicators in patients without thermoregulation disorders. In the former, EEG examination shows signs of increased activity of the thalamocortical system, which is expressed in a higher percentage of the a-index and the index of current synchronization.

A study of the state of the autonomic nervous system shows an increase in the activity of the sympathetic system, which is manifested by a spasm of the blood vessels of the skin and subcutaneous tissue according to plethysmography and skin thermotopography (thermal amputation phenomenon on the limbs), the results of an intradermal adrenaline test, GSR, etc.

Despite the advances in medicine in treating febrile infectious diseases, the number of patients with long-term persistent subfebrile fever of unknown genesis is not decreasing, but increasing. Among children aged 7 to 17, long-term subfebrile fever is observed in 14.5%, in the adult population - in 4-9% of those examined.

Hyperthermia is associated with a disorder of the central nervous system, which may be based on both psychogenic and organic processes. In organic lesions of the central nervous system, hyperthermia occurs with craniopharyngiomas, tumors, hemorrhage in the hypothalamus, traumatic brain injury, axial Gaie-Wernicke polyencephalopathy, neurosurgical (interventions, intoxications, as a rare complication of general anesthesia. Hyperthermic disorders against the background of severe mental illnesses. Hyperthermia is observed when taking medications - antibiotics, especially penicillin series, antihypertensive agents, diphenin, neuroleptics, etc.

Hyperthermia may occur with sudden overheating of the body (high ambient temperature), with the body temperature rising to 41 °C or more. In people with congenital or acquired anhidrosis, hydration and salt deficiency lead to disorders of consciousness and delirium. Central intense hyperthermia has an adverse effect on the body and disrupts the functioning of all systems - cardiovascular, respiratory, and metabolism. A body temperature of 43 °C or higher is incompatible with life. Damage to the spinal cord at the cervical level, along with the development of tetraplegia, leads to hyperthermia due to a disruption of temperature control, which is carried out by sympathetic nerve pathways. After the disappearance of hyperthermia, some thermoregulation disorders remain below the level of damage.

Hypothermia

Hypothermia is a body temperature below 35 °C, as well as hyperthermia, it occurs when the nervous system is disrupted and is often a symptom of autonomic dysfunction syndrome. Hypothermia is characterized by weakness and decreased performance. Autonomic manifestations indicate increased activity of the parasympathetic system (low blood pressure, sweating, persistent red dermographism, sometimes elevated, etc.).

As hypothermia increases (34 °C), confusion (pre-comatose state), hypoxia and other somatic manifestations are observed. A further decrease in temperature leads to death.

It is known that hypothermic reactions may occur in newborns and old people who are sensitive to temperature changes. Hypothermia may be observed in healthy young people with high heat loss (staying in cold water, etc.). Body temperature decreases with organic processes in the central nervous system with damage to the hypothalamus, which can lead to hypothermia and even poikilothermia. A decrease in body temperature is observed with hypopituitarism, hypothyroidism, parkinsonism (often combined with orthostatic hypotension), as well as with exhaustion and alcohol intoxication.

Hyperthermia can also be caused by pharmacological drugs that promote the development of vasodilation: phenothiazine, barbiturates, benzodiazepines, reserpine, butyrophenones.

Chill-like hyperkinesis

Sudden onset of chills (chills), accompanied by a sensation of internal trembling, increased pilomotor reaction ("goose bumps"), internal tension; in some cases combined with an increase in temperature. Chill-like hyperkinesis is often included in the picture of a vegetative crisis. This phenomenon occurs as a result of increased physiological mechanisms of heat production and is associated with increased activity of the sympathoadrenal system. The onset of chills is due to the transmission of efferent stimuli coming from the posterior parts of the hypothalamus through the red nuclei to the motor neurons of the anterior horns of the spinal cord. In this case, a significant role is given to adrenaline and thyroxine (activation of ergotropic systems). Chills can be associated with infection. Feverish chills increase the temperature by 3-4 °C, this is facilitated by the formed pyrogenic substances, i.e. heat production increases. In addition, it can be a consequence of psychogenic influences (emotional stress), which lead to the release of catecholamines and, accordingly, excitation, going along the indicated paths. The study of the emotional sphere in such patients reveals the presence of anxiety, anxiety-depressive disorders and symptoms indicating the activation of the sympathoadrenal system (pale skin, tachycardia, high blood pressure, etc.).

[ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 10 ]

Chill Syndrome

The "chills" syndrome is characterized by an almost constant feeling of "cold in the body" or in various parts of the body - the back, head. The patient complains that he is freezing, "goose bumps" run over the body. With the "chills" syndrome there are rather gross emotional and personal disorders (mental disorders), manifested by senestopathic-hypochondriacal syndrome with phobias. Patients do not tolerate and are afraid of drafts, sudden changes in weather, low temperatures. They are forced to constantly dress warmly, even at relatively high air temperatures. In the summer they wear winter hats, scarves, because "the head is cold", rarely take a bath and wash their hair. The body temperature is normal or subfebrile. Subfebrile temperature is long-term, low, monotonous, often combined with clinical signs of hypothalamic dysfunction - neurometabolic-endocrine disorders, impaired drives and motivations. Vegetative symptoms are represented by lability of arterial pressure, pulse, respiratory disorders (hyperventilation syndrome), increased sweating. The study of the vegetative nervous system reveals sympathetic insufficiency against the background of the dominance of the parasympathetic system.

Treatment of thermoregulation disorders

Thermoregulation disorders are most often manifested by hyperthermic disorders. Therapy should be carried out taking into account that hyperthermia is a manifestation of the syndrome of vegetative dysfunction. In this regard, the following measures are necessary:

1. Impact on the emotional sphere: the appointment of drugs that affect mental disorders, taking into account their nature (tranquilizers, antidepressants, etc.).
2. Prescription of drugs that reduce adrenergic activation, having both central and peripheral effects (reserpine 0.1 mg 1-2 times a day, beta-blockers 60-80 mg/day, alpha-blockers - pyrroxane 0.015 g 1-3 times a day, phentolamine 25 mg 1-2 times a day, etc.).
3. The use of drugs that enhance heat transfer by dilating the peripheral vessels of the skin: nicotinic acid, no-shpa, etc.
4. General strengthening treatment; physical hardening.

In case of chills syndrome, in addition to the above-mentioned drugs, it is advisable to prescribe neuroleptics.