Why hypothermia occurs
The main cause is exposure of the body to cold. Children are at higher risk due to thin skin, active blood supply, and a deficiency of subcutaneous fat. It is important to understand that hypothermia can occur even at positive ambient temperatures if humidity is high or clothing is wet.
- Primary: thermoregulation mechanisms are healthy, but the external impact is too severe.
- Secondary: thermoregulation is impaired due to CNS diseases, endocrine disorders (e.g., catecholamine deficiency), or muscle pathology.
Compensation stage: the fight for heat
The body strives to maintain normal temperature through:
- Behavioral reactions: seeking shelter and warmth.
- Decreased heat loss: constriction of skin blood vessels and cessation of sweating.
- Increased heat production: shivering (shivering thermogenesis) and activation of metabolism (non-shivering thermogenesis).
During this period, the neurohumoral system (hypothalamus, adrenal glands, thyroid gland) works to its limit to maintain temperature homeostasis.
Decompensation stage: failure
When adaptation is exhausted, the core temperature drops below 35 °C. The body becomes poikilothermic, meaning its temperature begins to depend on the environment. Three "vicious circles" develop:
| Type of circle | Mechanism |
|---|---|
| Metabolic | Cold → inhibits enzymes → heat production drops → cold intensifies |
| Vascular | Cold → vasomotor paralysis → vasodilation → increased heat loss |
| Neuromuscular | Cold → decreased excitability → cessation of shivering → heat drop |
The result is hypoxia, acidosis, and tissue edema, leading to coma and freezing to death.
Briefly: answers to topical questions
In which specific endocrine pathologies does secondary hypothermia develop?
Sources indicate that endocrine pathological conditions / risk factors for body cooling include:
- Adrenal insufficiency — due to catecholamine deficiency.
- Hypothyroid states.
These conditions are related to metabolic disorders / decreased exothermic processes and can contribute to the development of hypothermia under the influence of low ambient temperature.
"Shivering, vessels, hormones" — the three pillars of compensation: shivering warms, vessels preserve heat, hormones (catecholamines and thyroid) accelerate metabolism.
Class and exam questions
What is the difference between primary and secondary hypothermia?
In primary hypothermia, the body's thermoregulation mechanisms are intact. Secondary hypothermia develops when functions of the thermoregulatory center are already impaired.
Why does hypoxia develop during hypothermia?
Mixed hypoxia develops: circulatory (due to decreased cardiac output), respiratory (due to slowed breathing), hemic (due to hemoconcentration), and tissue (due to enzyme damage).
What is a "vicious circle" in hypothermia?
This is a pathological process in which a consequence of hypothermia (e.g., decreased metabolism) itself enhances the further drop in body temperature.
What else to study on this topic
- Features of thermogenesis in newborns (non-shivering thermogenesis).
- The role of the endocrine system in the stress response to cooling.
- Pathophysiology of microcirculatory disorders and sludge phenomenon.
- The effect of hypothermia on acid-base balance.
- Differential diagnosis of hypothermia stages according to WHO.
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Other topics in «Chapter 6. Body Thermal Balance Disorders»
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