Hypothermia
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Hypothermia is a medical condition in which the victim's core body temperature has dropped to significantly below normal and normal metabolism begins to be impaired. This begins to occur when the core temperature drops below 35 degrees Celsius (95 degrees Fahrenheit). If body temperature falls below 32 °C (90 °F), the condition can become critical and eventually fatal. Body temperatures below 27 °C (80 °F) are almost uniformly fatal, though body temperatures as low as 14 °C (57.5 °F) have been survived.
For unknown reasons, people who fall critically unconscious (and arguably die, though there are some who argue that any reversible condition is not, by definition, death) in very cold water can, in rare cases, be resuscitated, even though they would be expected to have died of drowning and/or hypothermia. See Mammalian diving reflex.
There are two types of hypothermia, acute and chronic. Acute hypothermia is the more dangerous; the body temperature goes down very swiftly, often in a matter of seconds or minutes, for example when a victim falls through an ice-covered lake. Chronic hypothermia occurs when the body temperature goes down over a longer period of time.
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Symptoms
- shivering - but only during the early stages
- dry, cold skin
- slow pulse
- slow breathing
- drowsiness - sometimes mistaken for drunkenness - which can lapse into coma.
Never assume someone has died, as at low temperatures the body can survive very much longer than at normal temperatures.
Treatment
Treatment for hypothermia involves raising the core body temperature of the victim.
First Aid Treatment
The first aid response to someone experiencing hypothermia, however, must be made with caution.
- Do not rub or massage the casualty
- Do not give alcohol
- Do not use hot water bottles or put the casualty in hot water
- Do not treat any frostbite
Any of these actions will divert blood from the critical internal organs and will worsen the situation.
What you should do:
- call the emergency services
- get the casualty to shelter
- replace wet clothing with warm, if it can be done rapidly.
- share body heat with the casualty by sharing a sleeping bag, survival bag, etc.
- give food and hot drinks
- monitor the casualty and be prepared to give Cardio-pulmonary resuscitation.
If the hypothermia has become severe, notably if the person is incoherent or unconscious, re-warming must be done under strictly controlled circumstances in a hospital. Bystanders should only remove the victim from the cold environment, including cold or wet clothing, and get the person to advanced medical care as quickly as possibly.
In hypothermia, the heart becomes extremely "irritable", and sudden re-warming can provoke cardiac arrhythmias, irregular beating of the heart in which blood isn't pumped adequately or may not be pumped at all. Common first aid wisdom in helping someone suspected of suffering from hypothermia is to treat them as if they were fragile, or made of glass — do nothing to over-stimulate the heart.
Hospital treatment
In a hospital, warming is accomplished gradually by internal administration of fluids under careful monitoring. If the victim starts to suffer irregular heartbeats, the equipment and personnel trained for providing the appropriate treatment are right at hand.
Prevention
In air, most heat is lost through the head, so hypothermia can be most effectively prevented by covering the head. Having appropriate clothing for the environment is another important prevention. Fluid-retaining materials like cotton, can be a hypothermia risk if the wearer gets sweaty on a cold day, then cools down and has sweat soaked clothing in the cold air. For outdoor exercise on a cold day, it is advisable to wear fabrics which can wick away sweat moisture. These include wool or synthetic fabrics designed specifically for rapid drying.
Heat is lost much more quickly in water. Children can die of hypothermia in as little as two hours in water as warm as 16C, typical of sea surface temperatures in temperate countries such as Great Britain. Many seaside safety information sources fail to quote survival times in water, and the consequent importance of wetsuits, possibly because the original research into hypothermia mortality in water was carried out in wartime Germany on unwilling subjects. There is an ongoing debate as to the ethical basis of using the data thus acquired. Information on wetsuits and safety in water can be found here. (http://first-wetsuit.co.uk/why.htm)
Medically induced
Hypothermia is sometimes induced deliberately as preparation for surgery or to maintain artificial coma to increase survival chances after severe injury.