Hypothermia (ICD-10-GM R68.0: Hypothermia not associated with low ambient temperature) is hypothermia. The entire body is affected.
Hypothermia describes the reduction of the core body temperature below the set point. This may be due to heat loss or heat extraction.
Hypothermia may be accompanied by frostbite.
Acute hypothermia is commonly observed in mountainous regions and countries with corresponding winter climates.In temperate climate countries, people with impaired thermoregulation (e.g., the elderly) and risk factors such as fatigue are at particular risk of developing hypothermia.
Therapeutic hypothermia by active cooling has protective effects, i.e., inhibition of the inflammatory immune response and thus reduced tissue damage. Therapeutic hypothermia is used during surgical procedures (e.g., cardiothoracic surgery) and to improve neurologic outcomes after resuscitation.
Three stages of hypothermia are distinguished:
| Stage | Rectal temperature | Stage description |
| I | 37-34 °C | Skin vascular contraction, heart rate and blood pressure increased, cold shivering |
| II | 34-27 °C | Increasing insensitivity to pain, heart rate and respiration slowed, muscle rigidity, reflexes weakened; unconsciousness (≤ 32 °C) |
| III | 27-22 °C | Autonomic body functions break down, death from cold |
Hypothermia can be a symptom of many diseases (see under “Differential diagnoses”).
For the severity of hypothermia according to the Swiss classification system, see under “Classification.”
Course and prognosis: The earlier hypothermia is treated, the more favorable the course. If the body temperature is raised in time and no complications such as cardiac arrhythmias occur, hypothermia usually has no consequences. In the course of severe hypothermia (stage III), cardiovascular failure as well as respiratory arrest may occur.
