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Hypothermia refers to any condition in which the temperature of a body drops below the level required for normal metabolism and/or bodily function to take place. In warm-blooded animals, core body temperature is maintained at or near a constant level through biologic homeostasis. When the body is exposed to colder temperatures, however, its internal mechanisms may be unable to replenish the heat that is being lost to the body's surroundings.
Hypothermia is the opposite of hyperthermia. Because the words sound alike, they are easily confused.
Stage 1: Body temperature drops by 1°C - 2°C below normal temperature C (1.8°-3.6°F, or between 96.8°F - 95°F). Mild to strong shivering occurs. Unable to perform complex tasks with the hands; the hands become numb. Blood vessels in the outer extremities contract, lessening heat loss to the outside air. Breathing becomes quick and shallow. Goose bumps form, raising body hair on end in an attempt to create an insulating layer of air around the body (limited use in humans due to lack of sufficient hair, but useful in other species). Often times, a person will expierence a warm sensation, as if they have recovered, but they are in fact heading into Stage 2.Another test to see if the person is entering stage 2 is if they are unable to touch their thumb with their little finger,this is first stages of muscles not working.
Stage 3: Body temperature drops below approximately 32°C or 90°F (normal is 37°C or 98.6°F). Shivering usually stops below 32°C; difficulty speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling are also usually present. Cellular metabolic processes shut down. Below 86°F (30°C) the exposed skin becomes blue and puffy, muscle coordination very poor, walking nearly impossible, and the victim exhibits incoherent/irrational behavior including terminal burrowing or even a stupor. Pulse and respiration rates decrease significantly but fast heart rates (ventricular tachycardia, atrial fibrillation) can occur. Major organs fail. Clinical death occurs. Because of decreased cellular activity in stage 3 hypothermia, the body will actually take longer to undergo brain death.
In a hospital, warming is accomplished by external techniques (blankets, warming devices) for mild hypothermia and by more invasive techniques such as warm fluids injected in the veins or even lavage (washing) of the bladder, stomach, chest and abdominal cavities with warmed fluids for severely hypothermic patients. These patients are at high risk for arrhythmias (irregular heartbeats), and care must be taken to minimize jostling and other disturbances until they have been sufficiently warmed, as these arrhythmias are very difficult to treat while the victim is still cold. An important tenet of treatment is that a person is not dead until they are warm and dead. Remarkable accounts of recovery after prolonged cardiac arrest have been reported in patients with hypothermia. This is presumably because the low temperature prevents some of the cellular damage that occurs when blood flow and oxygen are lost for an extended period of time.
In air, most heat is lost through the head;[2] hypothermia can thus 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, they will have sweat-soaked clothing in the cold air. For outdoor exercise on a cold day, it is advisable to wear fabrics which can "" 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 16°C (61°F, 289 K), typical of sea surface temperatures in temperate countries such as Great Britain in early summer. Many seaside safety information sources fail to quote survival times in water, as well as the consequent importance of diving suits. This is 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.
There is considerable evidence, however, that children who suffer near-drowning accidents in water near 0°C (32°F, 273 K) can be revived up to two hours after losing consciousness. The cold water considerably lowers metabolism, allowing the brain to withstand a much longer period of hypoxia.
Between 20 and 50 per cent hypothermal deaths are caused due to paradoxical undressing. The victim caught up in the snow develops this condition wherein they prefer to throw away the clothes they've been wearing before the help reaches them. The rescuers who are trained in mountain survival techniques have been asked to expect this. There have been quite a few published case studies of victims throwing off their clothes before the help reached them.
One possible explanation to this, even though a paradox, is that the fine blood vessels contracts in reaction to the presence of intense cold. This natural reaction reduces the loss of heat from the body by way of contraction.
Not much is know of this apart from the fact that it keeps itself well to its name: Paradoxical undressing. [3]