Hypothermia is defined as the situation in which the body temperature is below normal levels of the thermostat set point. In this situation, the thermoregulatory system begins to lose sensitivity and effectiveness, and therefore the body is not capable of producing enough heat. In other words: the cold sensors inform the hypothalamus about the dropping temperature. The heat producing activities are not sufficient and the cold sensors become insensitive because of the large temperature difference. This event leads to deregulation of the thermoregulatory centres in the hypothalamus. The individual begins a negative cascade of processes, in which cardiac and respiratory depression and neuronal disorders are likely.
Hypothermia can be a useful tool in surgery to decrease metabolic rate in a particular organ. An example is open-heart surgery.
Drowning victims are sensitive to hypothermia, because water absorbs energy 25 times better then air.
During heart surgery the cooled heart can be stopped beating for many minutes at a time.
In an advanced state of hypothermia the thermostat setpoint is below its normal value.