Adaptive and Pathogenic Effects
Fever is accompanied by two types of effects: protective (more common) and damaging.
Adaptive effects are aimed at combating infectious and non-infectious agents:
- Microbistatic and microbicidal action: at temperatures of 39–40 °C, microbial proliferation is suppressed.
- Stimulation of immune surveillance: production of immunoglobulins (Ig) and acute-phase proteins increases, and leukocyte proliferation and motility accelerate. This allows foreign agents to be detected and destroyed more rapidly.
- Activation of the stress response: specific and non-specific defense mechanisms are enhanced, and plastic processes in organs are altered.
Pathogenic effects occur at excessively high temperatures or due to the action of the pyrogenic 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 fluctuations, altered sensitivity to hormones, and increased vascular permeability.
- Overload of thermoregulatory systems: risk of syncope, circulatory collapse, and heart failure. In hypohydration (e.g., cholera) or massive hemolysis (e.g., malaria), hypercoagulation, microthrombosis, and disseminated intravascular coagulation (DIC) may occur.
- Impairment of other systems: loss of appetite, weight loss, headaches, seizures, and hallucinations.
Differences Between Fever and Exogenous Hyperthermia
It is important to clearly distinguish true fever from exogenous hyperthermia. Fever is a biologically purposeful reaction, whereas hyperthermia is a pathological process.
| Feature | 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 fluctuations | Preserved | Absent |
| Duration | May last weeks and months | Relatively short (leads to rapid decompensation and death) |
Principles of Treatment in Fever
Elevated temperature has an adaptive significance, so intensive antipyretic therapy is justified only when there is a threat of tissue damage. Treatment is based on three principles:
- Etiotropic. Aims to eliminate the pyrogenic agent. In infections, antimicrobial therapy is prescribed. In non-infectious conditions, the administration 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 resection).
- Pathogenetic. The goal is to block the mechanisms of temperature elevation. Cyclooxygenase (COX) inhibitors are used: acetylsalicylic acid, other NSAIDs, and pyrazolone derivatives. Agents that reduce excessive heat production (e.g., suppressing oxidative processes) may also be used.
- Symptomatic. Management of distressing symptoms (nausea, repeated vomiting, muscle and joint pain, arrhythmias). Analgesics, sedatives, and cardiotropic drugs are prescribed.
Pyotherapy
Pyotherapy is a treatment method using artificially induced hyperthermia. It is used both independently (per se) and in combination with other modalities.
For general pyotherapy, purified pyrogens (such as Pyrogenal) or stimulators of endogenous pyrogen synthesis are used. Moderate temperature elevation stimulates immune surveillance (effective in syphilis, gonorrhea, and arthritis) and triggers plastic and reparative processes in tissues, bones, and parenchymal organs following surgical interventions or during dystrophies.
Local pyotherapy improves regional blood flow, 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.