Fever - common reaction in many diseases, which is based on an imbalance, increase body temperature. Fever is accompanied by the violation of a number of body functions, including metabolism.
The mechanism fever is based on the reaction centres of thermoregulation (see), located in the hypothalamus. This reaction occurs in response to various stimuli exogenous and endogenous nature that are called pyrogens. However pyrogenic agents do not cause fever, if the centres of thermal destroyed or depressed (anesthesia, bromides, in some neuropsychiatric diseases, and so on). The degree temperature increase is usually proportional to the dose pyrogenic agents (chemical or bacterial toxins), but above 40,5-41 degrees, the temperature of the human body, as a rule, does not rise, and a further increase in dose of pyrogens causes atypical reactions characterized by a hypothermal phase. When the most severe toxic forms and stages of some acute infectious diseases feverish reaction does not occur. Poorly expressed, it is also among newborn children and patients of elderly and senile age.
Fever is an adaptive mechanism by which activate protective forces of the body.
Depending on the causes distinguish between infectious and non-infectious fever, but the pathogenesis of them are similar. Pyrogenic factors for infectious fever serve microbial toxins, metabolic products and the collapse of microbes.
Pyrogens, if ingested, induce the formation, mainly in granular leukocytes, secondary pyrogens - specific protein bodies, which in turn support a febrile reaction.
Fever is an infectious etiology can be called plant, animal or industrial poisons: lead, mercury, arsenic, and so on, to occur in allergic reactions - with idiosyncrasies (see), bronchial asthma, parenteral introduction of protein and other physical impacts, emotional upheaval, aseptic inflammation, necrosis and autolysis, and also diseases of the brain, particularly the hypothalamus, which had been a violation of thermoregulation.
Fever, especially in more severe cases, accompanied by violation of the functions of various organs and systems, primarily nervous system, which is manifested by headache, feeling of heaviness in the head, dimming or loss of consciousness. Suffer well as other systems of the body, there is increased heart activity and respiration, reducing diureza, etc. Metabolism at fever is also violated, can be increased basal metabolic rate, increased protein breakdown, and therefore increases the excretion of nitrogen with urine. However, keep in mind that a number of violations of functions and metabolism may depend not on fever as such, but from the development of the main disease.
Feverish reaction in its development passes through three stages: temperature increase, standing and its reduction. The duration of each stage is determined by many factors, in particular dose pyrogen, by the time of its validity, the violations that occurred in the organism under the influence of pathogenic agent, etc., Often fever is cyclical in nature (for example, malaria, recurrent fever)when after the described three stages for some time, the body temperature remains normal (pyrexia), and then rises again. Such cycles for disease can occur repeatedly.
Stage of temperature increase is a result of increasing heat production under the influence of pyrogens and reduce heat loss caused reflex spasm of skin vessels. In this regard, particularly when abrupt narrowing of blood vessels, patients experience a sensation of cold chills. Spasm of the blood vessels due to the paleness of fever. Muscle drugs for fever accompanied by an increase exchange and heat production in the muscles. The same mechanism causes and dragging pain in the muscles for a number of infectious diseases.
If you continue fever processes of heat production and heat transfer for some time balance each other, but then there is the second stage of fever - standing temperature. This stage is characterized by high heat (compared with a heat loss of healthy organism, heat production and in this stage is raised) - the expansion of blood vessels, causing pallor, followed by erythema, skin temperature increases, sensation of heat.
At termination, pyrogen on the body or suppressing its therapeutic means the heat production is reduced first of heat transfer and increased the level of the latter characterizes the third stage of fever - reducing temperature. In these cases, dramatically increases sweating, greatly expanding the blood vessels, which can lead to the collapse (see). However, these phenomena are observed only at sharp, so-called critical, the temperature drops. Often this temperature reduction occurs in the form of lysis, i.e. gradual reduction for several days. When lysis less pronounced listed signs and the threat of collapse becomes much smaller.
There are low-grade fever (up to 38 degrees), moderate (up to 39 degrees), high (up to 41 degrees) and gipertermiceski (over 41 degrees). In typical cases with acute infectious diseases the most favorable form is moderate fever, while the lack of it or giperpireccia indicate reduced reactivity of the organism (see) or the severity of the disease. In a typical development febrile reactions evening body temperature (17-20 hours.) exceeds the morning (4-6 hours). within 1 degree.

For various diseases febrile reactions can proceed in different ways, as reflected in various forms of temperature curves. In the clinic are usually of the following types of fevers.
1. A constant characteristic, for example, lobar pneumonia, maintained when the normal circadian rhythm temperature fluctuations not exceeding 1 degree, but sets it on a higher level.
2. Remittent or laxative observed at purulent diseases (exudative pleurisy, lung abscess, and others) with the amplitude of temperature within days to 2 degrees and more.
3. Intermittently, or intermittent, when the periods of normal temperature alternate with periods of increased temperature, and while the latter may be either a sharp increase and decrease the temperature, as with malaria, recurrent fever (recurrent fever), or a gradual increase with the same gradual decline, as if brucellosis (undulant fever).
4. Perverted at which the morning the temperature above the evening, that there is sometimes tuberculosis, protracted forms of sepsis and other diseases.
5. Hectic, or debilitating, with temperature up to 3-4 degrees occurring 2-3 times a day (at a particularly severe form of tuberculosis, sepsis, and so on).
6. Wrong, often occurring in many infectious diseases (rheumatism, influenza, dysentery), when the temperature changes are not detected any regularities.
Different types of fevers during illness can alternate, or jump from one to another.
In the treatment of fever sometimes prescribed antipyretics affecting the thermoregulation center (acetylsalicylic acid, amidopyrine and others); however, the main treatment should be cause, i.e. directed on liquidation of the underlying disease and the resulting violations of metabolic processes and functions. In some cases, the increase body temperature by activating the energy exchange, anxiety and other processes in the body, contributes to the implementation of adaptive reactions, thus creating favourable conditions for disease control; therefore, in such cases the use of fever-reducing should be limited.