Etiology of Hypothermia
The primary cause is exposure of the body to cold. In children, the risk is higher due to thin skin, active blood supply, and a deficiency of subcutaneous fat. It is important to note that hypothermia can occur even at positive ambient temperatures if humidity is high or clothing is wet.
- Primary: thermoregulatory mechanisms are healthy, but external exposure is excessively severe.
- Secondary: thermoregulation is impaired due to central nervous system diseases, endocrine disorders (e.g., catecholamine deficiency), or muscular pathology.
Compensation Stage: The Fight for Heat
The body strives to maintain normal temperature through:
- Behavioral responses: seeking shelter and warmth.
- Reduction of heat loss: cutaneous vasoconstriction and cessation of sweating.
- Enhancement of heat production: shivering (shivering thermogenesis) and activation of metabolism (non-shivering thermogenesis).
During this period, the neuroendocrine system (hypothalamus, adrenal glands, thyroid gland) works at its limit to preserve thermal homeostasis.
Decompensation Stage: Breakdown
When adaptation is exhausted, core temperature drops below 35 °C. The body becomes poikilothermic, meaning its temperature begins to depend on the environment. Three "vicious cycles" develop:
| Type of Cycle | 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 loss |
The result is hypoxia, acidosis, and tissue edema, leading to coma and freezing.