Hypothermia (from Greek ὑποθερμία) is when the body’s core temperature drops below . Symptoms depend on the temperature. In mild hypothermia there is shivering and mental confusion. In moderate hypothermia shivering stops and confusion increases. In severe hypothermia there may be paradoxical undressing, where a person removes their clothing, as well as an increased risk of the heart stopping. Hypothermia has two main types of causes. It classically occurs from extreme exposure to cold. It may also occur from any condition that decreases heat production or increases heat loss. Commonly this includes alcohol intoxication but may also include low blood sugar, anorexia, and advanced age among others. Body temperature is usually maintained near a constant level of through thermoregulation. Efforts increase body temperature involves shivering, increased voluntary activity, and putting on warmer clothing. Hypothermia may be diagnosed based on either a person symptoms in the presence of risk factors or by measuring a person’s core temperature. The treatment of mild hypothermia involves: warm drinks, warm clothing and staying active. In those with moderate hypothermia heating blankets and warmed intravenous fluids are recommended. People with moderate or severe hypothermia should be moved gently. In severe hypothermia extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass may be useful. In those without a pulse cardiopulmonary resuscitation (CPR) is indicated along with the above measures. Rewarming is typically continued until a person’s temperature is greater than . If there is no improvement at this point or the blood potassium level is greater than 12 mmol/liter at any time resuscitation may be discontinued. Hypothermia is the cause of at least 1500 deaths a year in the United States. It is more common in older people and males. One of the lowest documented body temperatures from which someone with accidental hypothermia has survived is in a near-drowning of a 7-year-old girl in Sweden. Survival after more than six hours of CPR has been described. In those in whom ECMO or bypass is used survival is around 50%. Deaths due to hypothermia have played an important role in many wars. Hyperthermia is the opposite of hypothermia, being an increased body temperature due to failed thermoregulation.
