Do I need to bring down the heat

Why, with every cold, do we study so carefully what the thermometer shows us? What determines the tactics of our further treatment to a greater extent: well-being or the numbers on the thermometer? And if, due to the characteristics of the body, the temperature during an infectious disease rises slightly, as it happens in older people, how can you determine how serious the situation is?

For us, an increase in body temperature is always an alarm, because it is quite often one of the symptoms of a disease. We understand that a decrease in temperature after taking antipyretics will not be an indicator of recovery. The correct approach to your health requires first identifying the possible cause of hyperthermia.

Causes of temperature increase

An increase in body temperature in response to any pathological effect is a non-specific reaction of the body that is needed to start and strengthen defense mechanisms. Under normal conditions, our body maintains a relatively constant temperature (temperature homeostasis). The body is protected from overheating by increasing heat transfer processes: intense sweating, expansion of subcutaneous capillaries. The restructuring of thermoregulation processes with reinstallation to a higher temperature level is fundamentally different from the body’s normal reaction to overheating and is called “fever”.

The thermoregulation center is located in the hypothalamus, and sometimes hyperthermia can develop with its direct damage (traumatic brain injury, brain tumors), but these are quite rare situations. In the vast majority of cases, the invasion of bacteria, viruses or other harmful substances into the body leads to the reinstallation of the thermoregulation center to a higher point. External and internal “irritants” of the thermoregulation center are called “pyrogens”. External (exogenous) pyrogens are certain substances that enter the body from the environment. Most often they are of an infectious nature: toxins and metabolic products of microorganisms. Internal (endogenous) pyrogens are formed in the body during inflammatory processes, allergic reactions, and the breakdown of tumor tissues. Thus, the range of diseases accompanied by an increase in body temperature is quite wide. ^[1].

Among the variety of pathologies, it is important to distinguish two main groups: infectious and non-infectious. Differentiation between “infectious” and “non-infectious” fever allows a combination of the clinical picture of the disease with laboratory parameters.

An increase in temperature due to an infectious process occurs in acute and chronic diseases caused by bacteria, viruses and fungi.

Non-infectious causes:

• after hemotransfusions (blood transfusion);
• after the introduction of vaccines, sera;
• in the presence of foci of aseptic (non-infectious) inflammation in the body (for example, with pancreatitis, gout, thrombophlebitis and other diseases);
• with allergic and autoimmune diseases;
• with the development of malignant tumors (including the hematopoietic system – leukemia), hyperthermia of the body is included in the concept of the so-called paraneoplastic reaction of the body;
• in the presence of extensive hematomas (hemorrhages) – an increase in temperature in this case is caused by increased destruction of blood cells (erythrocyte hemolysis);
• in the presence of necrotic (dead) tissues (for example, with myocardial infarction);
• in case of damage to the thermoregulation center in the brain (for example, after a traumatic brain injury or in the presence of a brain tumor);
• with some endocrine diseases (for example, with hyperthyroidism – a pathology of the thyroid gland, accompanied by its hyperfunction) ^[2].

Temperature rise rates

The degree of increase depends on many factors, including the state and reactivity of the body, concomitant intoxication.

A slight increase in body temperature in some cases is a normal reaction of the body: with intense physical exertion, after eating, with strong emotional stress, in women during ovulation (increase by 0,6-0,8˚C). High ambient temperature also causes hyperthermia: in hot weather, the body temperature is 0,1-0,5˚C higher than in cold weather.

The normal body temperature of an adult fluctuates throughout the day, remaining in the range of 36 – 37˚C (when measured in the armpit). The acceptable range of daily fluctuations is usually 0,1-0,6˚C and should not exceed 1˚C. The maximum body temperature is recorded in the evening from 17 to 21 hours, and the minimum – in the morning from 3 to 6 hours.

Elevated body temperature from 37 to 38˚C is called subfebrile (from Latin sub under, below + febris fever). Moderately elevated from 38 to 39˚C is called febrile. High from 39 to 41˚C is called pyretic (from Greek pyretos heat). Excessively high body temperature above 41˚C is called hyperpyretic ^[1].

What is the danger of excessive temperature rise

In addition to the destructive effect on pathogenic microorganisms and the stimulation of the immune response, high temperature has a number of negative effects.

Hyperthermia changes metabolism, causes loss of water and salts. When the body overheats, the process of sweating increases significantly. Loss of fluid is accompanied by thickening of the blood, increasing the risk of blood clots.

High temperatures pose a great danger to people with cardiovascular disease. With its increase by 1˚C, the pulse increases by 8-10 beats per minute. The heart works at a high frequency, under adverse conditions of blood clotting and metabolic disorders. Sometimes, with hyperthermia in patients with cardiac pathology, rhythm disturbances are recorded, which is due to the activation of the sympathetic-adrenal system and electrolyte imbalance.

In temperature patients, frequent shallow breathing is observed: the frequency of respiratory movements increases, but the depth of inspiration decreases. Not enough oxygen enters the organs and tissues, hypoxia develops.

High temperature accelerates redox processes, which means that the oxygen demand of cells increases sharply: with an increase in temperature by 0,6˚C, the level of basal metabolism increases by approximately 10%. Due to the lack of oxygen in the cells, a large number of “acidic” metabolites are formed, which disrupt the function of tissues and organs. Such a failure of metabolic processes, leading to the “acidification” of the body, is called “acidosis”. That is why fever can be accompanied by intoxication. This is most often observed in children, but if the inflammatory process proceeds for a long time, intoxication also occurs in adults.

With an increase in the activity of metabolic processes, carbohydrate reserves are primarily used, after their reserves are exhausted, fats and proteins are used. As a result of the increased breakdown of proteins, their loss of up to 300-400 grams per day is possible. Therefore, with a fever, it is necessary to give children easily digestible carbohydrates (for example, juices).

With hyperthermia, the function of the gastrointestinal tract is inhibited: appetite decreases, secretion of enzymes decreases, motility and absorption processes are impaired. As a result, the development of a syndrome of impaired absorption and constipation is possible. This is especially unfavorable for elderly patients.

Patients with high body temperature are threatened by dangerous conditions of the central nervous system, due to an increase in the permeability of the blood-brain barrier and insufficient oxygen supply to the brain. Hyperthermia may be accompanied by agitation. The most dangerous complication that occurs in children with an immature thermoregulation system is febrile convulsions. ^{[3] [4] [5]}.

What temperature should be lowered and what should not

An increase in temperature is an evolutionary defense mechanism against pathogenic microorganisms. Upon contact with viruses, bacteria and their toxins, cells of the immune system (leukocytes) produce special substances that trigger an inflammatory response. The temperature reaction is accompanied by a number of characteristic changes in metabolism and physiological functions aimed at enhancing cellular and humoral immunity. Under conditions of high temperature, antibodies and defense cells are more actively produced, the reproduction of viruses and bacteria is inhibited. Many pathogens become sensitive to antibacterial drugs only at elevated temperatures. Its unreasonable decrease suppresses the severity of the immune response. However, very high temperatures pose a danger to the body. Hyperthermia above 40˚C can lead to the development of cerebral edema and dysfunction of vital organs.

The threshold temperature at which it is necessary to make a decision on taking antipyretic drugs is considered to be from 38˚C and above. But each person tolerates hyperthermia differently. Therefore, you should focus on well-being and the presence of concomitant diseases. This is especially important in relation to children.

The rise in body temperature above 38˚C is dangerous for children in the first 6 months of life, as well as for children from 6 months. up to 3 years, included in the risk group for the development of febrile seizures. In accordance with the recommendations, antipyretic therapy is prescribed for children of the first 3 months of life at temperatures above 38,0˚C, for children older than 3 months (previously healthy) – above 39,0˚C.

In adult patients with severe diseases of the respiratory, cardiovascular and central nervous systems, the course of which may worsen with fever, a decrease in temperature above 38,0˚C is indicated.

For young people without comorbidity, antipyretic drugs are indicated at 39,0˚C and above.

The question of choosing a drug is decided in each case individually. ^{[6] [7]}.

Fever in newborns

Separately, it should be said about the increase in temperature in newborns and children of the first year of life.

Immediately after birth, the child’s body is quite ready for independent thermoregulation. In newborns, sweating and the ability to vasomotor reactions are sufficiently developed. However, an imbalance between heat production and heat loss develops in infants more often than at a later age. In the first year of life, due to insufficiently expressed subcutaneous adipose tissue and a relative increase in the specific surface of the body, the process of heat transfer always prevails. An additional increase in heat generation is carried out in newborns due to increased oxidative processes in brown adipose tissue (non-shivering thermogenesis). They do not have contractile thermogenesis (the ability to increase heat production due to involuntary muscle contraction). During the day after birth, children show the ability to develop fever, but at first it is less pronounced than at an older age. Therefore, infectious diseases in infants may not be accompanied by a significant increase in body temperature, but if this occurs, it indicates the seriousness of the disease. ^[8].

Temperature in COVID-19

The initial manifestations of coronavirus infection are similar to the course of many acute respiratory viral infections. Weakness, headache and muscle pain may come first, followed by catarrhal manifestations: nasal congestion, slight sore throat. Then, as with many SARS, the temperature rises from 37˚C to 39˚C. This reaction of the body is recorded in most patients with COVID-19. The duration and level of temperature rise during infection with SARS-CoV-2 depends on many factors: the immune response, the amount of the pathogen that has entered the body, and developing complications. Some carry the infection without a significant increase.

The temperature response in COVID-19 is the body’s natural response, mobilizing the immune system upon contact with the virus. Therefore, it is not recommended to take antipyretic drugs at a temperature below 38,5˚C, except in situations where the patient does not tolerate an increase in temperature.

As a rule, fever lasts 1-3 days, sometimes up to 5-6 days. If it is above 37,5˚C for five days in a row, this is a reason to seek medical help, since a more severe course of the disease with the development of complications is possible.

If a young person has a high temperature without concomitant chronic pathology, he can call a doctor at home to assess the condition and prescribe appropriate therapy.

If a temperature above 37,5˚C persists for several days in people over 65 years of age or with serious concomitant diseases, an ambulance should definitely be called for transportation to a hospital.

One of the serious consequences of the new coronavirus infection is hyper-inflammatory reactions. This is an overactive immune response triggered by the SARS-CoV-2 virus.

An indirect sign of the development of a hyperinflammation reaction may be a return rise in temperature. Febrile fever above 38 degrees after normalization of temperature is also a reason to call a doctor at home.

A sharp increase in temperature over 38˚C with a significant deterioration in well-being and the addition of shortness of breath are indications for calling an ambulance team and urgent hospitalization.

A feature of the course of COVID-19 is the long-term preservation of subfebrile temperature (not higher than 37 degrees). Subfibrillation can persist up to a month in the process of recovery. In this case, in the absence of other symptoms and satisfactory health, complications are unlikely. ^{[9] [10] [11]}.

When to see a doctor

Young people without comorbidities should seek medical help for hyperthermia above 39˚C. Patients belonging to risk groups (elderly, with chronic diseases, small children, pregnant women) should call a doctor at home already with low-grade 37,9˚C and moderate 38,0-39,0˚C fever, for timely appointment therapy.

An ambulance team must be called in case of development of severe intoxication, signs of respiratory, cardiac, renal or multiple organ failure.

Emergency medical care is required for fever patients with any signs of damage to the central nervous system (confusion, agitation or lethargy, convulsions).

If a fever above 38,5˚C is not stopped by antipyretic drugs at the recommended age dosages within 48 hours, it is also worth calling an ambulance team so that the doctors can provide emergency care and decide on hospitalization ^[12].

Conclusions

An increase in temperature is a signal of the body about danger, which should not be ignored. A serious cause for concern is hyperthermia in vulnerable populations (children, the elderly, pregnant women). But even at a young age and in the absence of chronic diseases with an increase in temperature, you should seek medical help.

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