Signs of fever

The type of high fever (fever) is an important characteristic of any disease. Fevers are distinguished by duration. Acute fever lasts up to 2 weeks, subacute - up to 6 weeks, chronic fever can last more than 6 weeks. According to the degree of increase in body temperature, there are:

• subfebrile - up to 38 °C;
• moderate - up to 39 °C;
• febrile - up to 41 °C;
• hyperpyretic - over 41 °C.

The type of fever is an important characteristic of any disease. According to the nature of the temperature curve fluctuations, the following types of fever are distinguished:

• persistent fever, in which the temperature rises to 39-40 °C and remains at the same level for several days or weeks, and daily fluctuations do not exceed one degree;
• intermittent fever, which is characterized by temperature fluctuations of at least 1° C, while the temperature can reach normal limits;
• remittent fever, in which daily changes in body temperature may be similar to intermittent fever, but unlike the latter, the temperature does not drop to normal values;
• hectic fever, which is accompanied by a rise in temperature above 40 °C and its rapid decrease to subfebrile numbers;
• atypical fever, in which the increase in body temperature from high to moderately high values occurs without a specific pattern.

Several factors influence the change in temperature during the day. The decisive factor is the amount of pyrogens and the sensitivity of the thermoregulation center to them. In addition, the state of the heat transfer system and the trophic innervation system are important. The process of formation of substances - oxidative phosphorylation uncouplers, as well as the reserve of energy material - adipose tissue in the body, play a significant role.

It is known that the child's body temperature is not the same in different places of its measurement. Immediately after birth, the temperature in the rectum fluctuates within the range of 36.6-38.1 °C, in the first day - 36.5-37.4 °C, on the second day - 36.9-37.4 °C. Subsequently, the temperature range remains more or less constant, with small deviations towards a decrease or increase. In the armpit, compared to the rectum, the temperature is lower by 0.3-0.6 °C, and in the mouth - by 0.2-0.3 °C.

Newborns have insufficiently developed thermoregulation, especially underdeveloped heat transfer mechanisms. As a result, they easily overheat and overcool.

In some infectious diseases, birth injuries, surgical interventions in newborns and children of the first year of life, hyperthermic syndrome may develop, manifested by a sharp increase in temperature, accompanied by convulsions and disorders of the central nervous system, posing a serious danger to life. Hyperthermic syndrome in children of the first year of life is not a true increase in temperature, since the mechanisms of thermoregulation at this age are insufficiently developed, as a result of which an increase in heat production is observed against the background of intoxication. Hyperthermic syndrome in newborns can occur with infectious neurotoxicosis, metabolic acidosis, cerebral microcirculation disorders, cerebral edema and other conditions that have a damaging effect on the hypothalamic thermoregulation center.

A rapid increase in temperature in a child is associated with the high intensity of metabolic processes in the child’s body.

In children in the first months of life, the insufficient level of maturation of the cerebral cortex and its protective and regulatory functions causes an increased impact of any physical factor on the body.

One of the most serious complications of high temperature is febrile seizures. The average population risk of febrile seizures is 3% and increases with a history of febrile seizures in childhood. The temperature at which seizures occur usually ranges from 38.5°C to 41°C (average 39.3°C). Seizures most often occur in the first 12-24 hours after the temperature rises, usually at the height of the fever.

Febrile seizures account for 85% of all seizure syndromes in children. Children aged 17-23 months are most susceptible to seizures. In 15% of cases, febrile seizures are observed at the age of up to 4 years. The periods of maximum probability of febrile seizures occur in the 4-5th, 7-8th, 11-12th months of a child's life. Most often, febrile seizures occur in children against the background of ischemic-hypoxic encephalopathy.

The occurrence of febrile seizures is caused by intracerebral hyperosmolarity and edematous syndrome. Hyperthermia and developing hypoxia contribute to the disruption of energy metabolism, phospholipid metabolism in brain tissue, activation of LPO processes, stimulation of the synthesis of prostaglandin F2, which causes spasm of cerebral vessels and, along with prostaglandin E1, affects the thermoregulatory center. Hence, there is a need to use antiprostaglandin drugs as a pathogenetic treatment for febrile seizures.

At high temperature, a vegetative imbalance develops, manifested by sympathetic activation. An increase in the tone of the sympathetic division of the autonomic nervous system causes an increase in heart rate by 8-10 beats per 1 °C increase in body temperature. Spasm of peripheral vessels, observed at the initial stage of fever, leads to an increase in blood pressure. The predominance of excitation of the sympathetic or parasympathetic divisions of the autonomic nervous system at different stages of fever causes a decrease in the secretory activity of all digestive glands, motor disorders of the stomach and intestines, and a change in intestinal tone.

High temperature affects the central nervous system. Both depression and activation of higher nervous activity may occur. The clinical picture includes headache, drowsiness, apathy, hyperesthesia. Young children may have delirium and hallucinations.

The febrile process can affect the respiratory function by increasing the respiratory rate. For every 1 °C above 37 °C, the number of respiratory movements increases by 4 breaths per minute, and the heart rate increases by 20 beats.

Despite this, the oxygen supply no longer meets the growing tissue needs, and relative hypoxia eventually develops. The degree of hyperthermia at which these disorders occur is very variable. Most often, it corresponds to a body temperature of 39-40 °C, but depends on the individual characteristics of the child's body. The younger the child, the more severe the neonatal period was (especially if there are already associated injuries), the earlier decompensation develops.

In febrile conditions, a negative nitrogen balance is often detected - an increase in the excretion of nitrogenous metabolic products in the urine. The reasons for this are intoxication with increased protein catabolism and starvation caused by a decrease in appetite and deterioration in the digestibility of food. The predominance of catabolic processes over anabolic ones is also associated with the action of endogenous pyrogens, IL-1 and TNF-alpha. These cytokines are also responsible for reducing the activity of lipoprotein kinase and blocking neolipogenesis in adipose tissue. Changes in the carbohydrate process occur mainly due to the activation of the hypothalamic-pituitary-adrenal system. Glycogenolysis processes are activated in the liver, glycogen reserves decrease, and hyperglycemia is noted in the blood.

High temperature is often accompanied by changes in water and electrolyte balance. At stage I, increased renal blood flow is accompanied by increased diuresis. At stage II, diuresis decreases, and water is retained. Due to increased secretion of aldosterone, the excretion of sodium ions from the body is limited, and, accordingly, fewer chlorine ions are released. At stage III of fever, diuresis increases again, and the secretion of water, sodium ions, and chlorine by sweat glands increases.

It is advisable to consider each increase in temperature from a prognostic standpoint.

If heat production corresponds to heat emission, the child develops a favorable, so-called "pink" fever. It got its name from the color of the patient's skin. The skin is moderately hyperemic, warm, moist to the touch. The child's behavior practically does not change.

If, against the background of hyperthermia, the patient feels cold, chills, his skin is pale, with a cyanotic tint of the nail beds and lips, the extremities are cold, and the increase in body temperature progresses, then this is "pale" fever. It is accompanied by tachycardia, shortness of breath, and convulsions are possible.

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