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Fever

Fever is a general reaction of the body in many diseases, which is based on a violation of heat balance, and therefore increases body temperature . Fever is accompanied by a violation of a number of body functions, including metabolism.

The mechanism of fever is based on the reaction of thermoregulation centers (see) located in the hypothalamus. This reaction arises in response to the action of various exogenous and endogenous stimuli, which are called pyrogens. However, pyrogenic agents do not cause fever if the thermoregulation centers are destroyed or depressed (with anesthesia, bromides, with some neuropsychiatric diseases, etc.). The degree of temperature increase is usually proportional to the dose of pyrogenic agents (chemicals or bacterial toxins), but above 40.5–41 ° the temperature of the human body, as a rule, does not rise, and a further increase in the dose of pyrogens causes an atypical reaction, characterized by a hypothermic phase. With the most severe toxic forms and stages of some acute infectious diseases, a febrile reaction does not occur. It is also weakly expressed in newborns and in patients of elderly and old age.

Fever is an adaptive mechanism by which the body's defenses are activated.

Depending on the cause, infectious and non-infectious fevers are distinguished, but their pathogenesis is similar. Pyrogenic factors in infectious fever are microbial toxins , metabolic products and the breakdown of microbes.

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Pyrogens, entering the body, cause the formation, mainly in granular leukocytes, of secondary pyrogens - specific protein bodies, which in turn support a febrile reaction.

Fever of non-infectious etiology can be caused by plant, animal or industrial poisons: lead , mercury , arsenic, etc., occur during allergic reactions - with idiosyncrasy (see), bronchial asthma, parenteral administration of protein, etc., physical influences, emotional shocks, aseptic inflammations, necrosis and autolysis, as well as brain diseases, in particular the hypothalamus, in which there is a violation of thermoregulation.

Fever, especially in more severe cases, is accompanied by dysfunction of various internal organs and systems, primarily the nervous system, which is manifested by headache, a feeling of heaviness in the head, dizziness or loss of consciousness. Other systems of the body also suffer, there is an increase in cardiac activity and respiration, a decrease in diuresis, etc. The metabolism during fever is also disturbed, the basal metabolism can be increased, the breakdown of proteins increases, and therefore the excretion of nitrogen with urine increases. However, it should be borne in mind that a number of dysfunctions and metabolism may depend not on the fever itself, but on the development of the underlying disease.

The febrile reaction in its development goes through three stages: an increase in temperature, its standing and a decrease. The duration of each stage is determined by many factors, in particular, the dose of pyrogen, its duration of action, disorders that have arisen in the body under the influence of a pathogenic agent, etc. Often, fever is cyclical (for example, malaria, relapsing fever ) when three stages for some time the body temperature remains normal (apyrexia), and then rises again. Such cycles during the course of the disease may occur more than once.

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The stage of temperature increase is the result of increased heat production under the influence of pyrogens and a decrease in heat transfer caused by reflex spasm of skin vessels. In this regard, especially with a sharp narrowing of blood vessels, patients experience a feeling of cold - chills. A spasm of the vessels explains the pallor of the fever. Muscle tremor during fever is accompanied by increased metabolism and heat production in the muscles. The same mechanism causes pulling pain in muscles in a number of infectious diseases.

With the continuation of fever, the processes of heat production and heat transfer for some time counterbalance each other, but then a second stage of fever arises - standing temperature. This stage is characterized by increased heat transfer (compared with that of a healthy organism, heat production is also increased in this stage) - vasodilation, as a result of which pallor is replaced by hyperemia, the skin temperature rises, a sensation of heat appears.

When pyrogen is terminated on the body or its therapeutic means are suppressed, heat production decreases before heat transfer and the increased level of the latter characterizes the third stage of fever - a decrease in temperature. In these cases, sweating increases sharply, the vessels dilate significantly, which can lead to collapse (see). However, these phenomena are observed only with a sharp, so-called critical, decrease in temperature. Often, this decrease in temperature occurs in the form of lysis, that is, a gradual decrease over several days. During lysis, the listed symptoms are less pronounced and the threat of collapse becomes much less.

There are subfebrile fever (up to 38 °), moderate (up to 39 °), high (up to 41 °) and hyperperitoneal (over 41 °). In typical cases with acute infectious diseases, the most favorable form is moderate fever, while the lack of it or hyperpyrexia indicates a reduced reactivity of the body (see) or the severity of the disease. With a typical development of febrile reaction, evening body temperature (at 17–20 hours) exceeds morning (at 4–6 hours) within 1 °.

In various diseases, febrile reactions can occur in different ways, which is reflected in various forms of temperature curves. The clinic usually distinguishes the following types of fever.
1. Constant, characteristic, for example, for croupous pneumonia, when the normal daily rhythm of temperature is maintained with fluctuations not higher than 1 °, but it is set at a higher level.
2. Remitting, or laxative, observed in purulent diseases (exudative pleurisy , lung abscess, etc.) with an amplitude of temperature within 24 hours up to 2 ° and more.
3. Intermittent, or intermittent, when periods of normal temperature alternate with periods of elevated temperature, and during the latter either a sharp rise and fall in temperature can be observed, as in malaria, recurrent typhoid fever (recurrent fever), or its gradual rise with the same gradual decrease as with brucellosis (wavy fever).
4. Perverted, at which the morning temperature is higher than the evening temperature, which is sometimes observed in tuberculosis, prolonged forms of sepsis and some other diseases.
5. Hectic, or debilitating, with temperature changes of up to 3-4 ° occurring 2-3 times a day (for especially severe forms of tuberculosis, sepsis, etc.).
6. Incorrect, quite common in many infectious diseases ( rheumatism , influenza, dysentery), when no regularity is found in temperature fluctuations.

Different types of fevers during an illness can alternate or turn into one another.

In the treatment of fever, it is sometimes prescribed antipyretics that affect the thermoregulation centers (acetylsalicylic acid, amidopyrine , etc.); however, the main treatment should be causal, i.e. it is aimed at eliminating the underlying disease and the metabolic processes and functions caused by it. In some cases, an increase in body temperature, activating energy metabolism, excitability and other processes in the body, contributes to the implementation of adaptive reactions, thereby creating favorable conditions for combating the disease; therefore, in such cases, the use of antipyretic should be limited.