Adaptive and pathogenic effects
Fever is accompanied by two types of effects: protective (more common) and damaging.
Adaptive effects aim to combat infectious and non-infectious agents:
- Microbistatic and microbicidal action: at temperatures of 39–40 °C, microbial reproduction is suppressed.
- Stimulation of immunobiological surveillance (IBS): production of immunoglobulins (Ig) and acute-phase proteins increases, and leukocyte proliferation and motility accelerate. This allows for faster detection and destruction of foreign agents.
- Activation of the stress response: specific and non-specific defense mechanisms are enhanced, and plastic processes in organs are altered.
Pathogenic effects occur when the temperature is excessively high or due to the action of the fever cause itself (e.g., microbial toxins or foreign proteins):
- Direct cell damage due to high temperature.
- Development of immunopathological processes: allergies, immunodeficiencies, or autoimmune diseases.
- Biologically inappropriate reactions: blood pressure spikes, changes in hormone sensitivity, and increased vascular permeability.
- Overload of thermoregulation systems: risk of syncope, collapse, heart failure. In case of hypohydration (cholera) or massive hemolysis (malaria), hypercoagulation, microthrombosis, and DIC syndrome are possible.
- Disruption of other systems' functions: loss of appetite, weight loss, headaches, seizures, and hallucinations.
Differences between fever and exogenous hyperthermia
It is important to clearly distinguish between true fever and exogenous overheating of the body. Fever is a biologically purposeful reaction, whereas hyperthermia is a pathological process.
| Sign | Fever | Exogenous hyperthermia |
|---|---|---|
| Cause | Action of pyrogens | High ambient temperature |
| Key mechanism | Shift of the thermoregulatory "set point" | Failure of adaptation mechanisms to exogenous heat |
| Diurnal variations | Preserved | Absent |
| Duration | Can last for weeks and months | Relatively short (leads to rapid decompensation and death) |
Principles of fever management
Temperature elevation has adaptive significance, so intensive antipyretic therapy is justified only when there is a threat of bodily damage. Treatment is based on three principles:
- Etiotropic. Aims to eliminate the pyrogenic agent. In infections, antimicrobial therapy is prescribed. In non-infectious etiology, the introduction of exogenous pyrogens (whole blood, vaccines, sera) is stopped, or the source of endogenous pyrogens is surgically removed (drainage of an abscess, excision of necrotic tissue, tumor removal).
- Pathogenetic. The goal is to block mechanisms of temperature elevation. Cyclooxygenase (COX) blockers are used: acetylsalicylic acid, other NSAIDs, pyrazole derivatives. Agents that reduce excessive heat production (e.g., suppressing oxidative processes) may also be used.
- Symptomatic. Combating distressing manifestations (nausea, recurrent vomiting, muscle and joint pain, arrhythmias). Analgesics, tranquilizers, and cardiotropic drugs are prescribed.
Pyiotherapy
Pyiotherapy is a method of treatment using the artificial induction of hyperthermia. It is used both independently (per se) and in combination with other interventions.
For general pyiotherapy, purified pyrogens (e.g., the drug Pyrogenal) or stimulants of endogenous pyrogen synthesis are used. Moderate temperature elevation stimulates the IBS system (effective in syphilis, gonorrhea, arthritis) and triggers plastic and reparative processes in tissues, bones, and parenchymal organs after surgical interventions or in dystrophies.
Local pyiotherapy improves regional blood circulation, stimulates local defense mechanisms, and promotes healing. It is indicated for chronic inflammation, erosions, and ulcers of the skin and subcutaneous tissue. In oncology, the method is used due to its potential antitumor effect.
To remember the three principles of fever management, use the acronym EPS: Etiotropic (remove the cause), Pathogenetic (lower temperature with NSAIDs), Symptomatic (relieve pain).
Class and exam questions
Is it always necessary to bring down a high temperature during fever?
No. Fever has adaptive significance. Antipyretic drugs are needed only when hyperthermia begins to exert a damaging effect on the body's vital activity.
How does fever fundamentally differ from overheating (hyperthermia)?
Fever involves a temporary dynamic restructuring of the thermoregulation system (a shift of the "set point") under the action of pyrogens. In hyperthermia, however, there is a failure of adaptation mechanisms due to external heat.
Why can DIC syndrome develop during infectious fever?
This is due to the functional overload of the body's systems against the background of pronounced hypohydration (e.g., in cholera) or massive destruction of erythrocytes (in malaria), which leads to hypercoagulation and the formation of microthrombi.
What else to study on this topic
- Immunopathological consequences of fever: allergies and autoimmune diseases
- Changes in tissue sensitivity to hormones and neurotransmitters during fever
- Influence of microbial endo- and exotoxins on the development of the febrile response
- Features of hemostasis disorders in malaria and cholera
- Mechanisms of the antitumor effect of local pyiotherapy
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