Definition/Introduction
Synonym: Hypothermia Hypothermia can affect individual body regions as well as the entire body. Exposed parts of the body, such as hands, feet, ears and the nose (acra) are particularly at risk of hypothermia. If the entire body cools down, one speaks of hypothermia from a core body temperature below 36°C. Permanent hypothermia can lead to frostbite and a life-threatening condition.
Thermal regulation
The body is normally able to keep its temperature stable within a range of 36.4°C – 37.4°C. During the day, the body temperature fluctuates within these limits, with the lowest values being reached during the night. In the early morning, the body temperature rises again; if the core body temperature drops too much, the body starts to counterregulate.
This means that the skin and extremities (arm and leg) in particular are supplied with less blood. In extreme cases, only the vital organs are supplied with blood and thus kept warm (centralization). In addition, the body tries to produce heat by the so-called cold shivering, i.e. a rhythmic contraction of the thin muscles in the skin. Due to their unfavorable ratio of body surface to body volume, newborns are particularly at risk of cooling down and therefore have a layer of brown fatty tissue which an adult no longer has. This brown fat can be used particularly well for heat production and protects the newborn from dangerous hypothermia.
Causes
If the heat output exceeds the heat produced by the body, the core body temperature drops. The body is no longer able to compensate for the heat loss and this can ultimately lead to hypothermia. Typically, a lowered core body temperature occurs during prolonged exposure to cold environments without adequate clothing.
There are five causes that can lead to heat loss:
- Convection – Body heat is transferred to the colder ambient air; the effect increases with wind.
- Conduction – The body heat is transferred to a colder body and the bodies continue to equalize their temperatures until they equalize.
- Respiration – The body loses heat when breathing, as warmed air leaves the body and cold air flows in when breathing in, which in turn needs to be warmed.
- Perspiration – Due to the constant evaporation of liquid on the body surface, the body cools down. At high outside temperatures, the body promotes this heat loss through increased sweating; at cold temperatures, however, the cooling down is unintentionally accelerated.
- Radiation – As with any energy producing process, the body loses heat in the form of thermal radiation. Clothing can act as an insulating material and retain the heat radiation.