| Hypothermia is a condition in which an
organism's temperature drops below that required for normal metabolism and
bodily functions. In warm-blooded animals, core body temperature is
maintained near a constant level through biologic homeostasis. But when
the body is exposed to cold its internal mechanisms may be unable to
replenish the heat that is being lost to the organism's surroundings.
Symptoms.
Hypothermia can be divided
in three stages of severity.
In stage 1, body temperature drops by 1-2°C below normal temperature
(35-38°C). Mild to strong shivering occurs. The victim is unable to
perform complex tasks with the hands; the hands become numb. Breathing
becomes quick and shallow. Goose bumps form. Often, a person will
experience 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 the first stage of muscles not working.
In stage 2, body temperature drops by 2-4°C. Shivering becomes more
violent. Muscle mis-coordination becomes apparent. Movements are slow and
labored, accompanied by a stumbling pace and mild confusion, although the
victim may appear alert. The victim becomes pale. Lips, ears, fingers and
toes may become blue.
In stage 3, body temperature drops below approximately 32 °C (89.6 °F).
Shivering usually stops. Difficulty speaking, sluggish thinking, and
amnesia starts to appear; inability to use hands and stumbling is also
usually present. The exposed skin becomes blue and puffy, muscle
coordination becomes very poor, walking becomes almost 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.
This condition can unexpectedly occur on a summer hike in the
mountains. If you get caught in a summer shower and get wet,
hypothermia can easily and quickly occur. Be very aware of your
conditions and those of others.
Treatments.
Treatment for hypothermia consists of drying, sheltering, and gradually
warming (making sure to not rub the patient's body, to warm with blankets
and, if possible, to transfer your own body heat). While blankets help a
person retain body heat, they are not sufficient to treat hypothermia. It
is vital that you warm the core of the body first or the cold blood will
be forced towards the heart and may cause death. In the field, a mildly
hypothermic person can be effectively re-warmed through close body contact
from a companion and by drinking warm, sweet liquids.
Moderate and severe cases of hypothermia require immediate evacuation
and treatment in a hospital. In hospital, warming is accomplished by
external techniques such as heated blankets 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.
Prevention.
Appropriate clothing helps to prevent hypothermia. Wearing cotton in
cool weather is a particular hypothermia risk as it retains water, and
water rapidly conducts heat away from the body. Even in dry weather,
cotton clothing can become damp from perspiration, and chilly after the
wearer stops exercising. Synthetic and wool fabrics provide far better
insulation when wet and are quicker to dry. Some synthetic fabrics are
designed to wick perspiration away from the body. In air, most heat (20 to
40 percent) is lost through the head; covering the head and neck is quite
important in reducing the likelihood of hypothermia.
Heat loss on land is very difficult to predict due to multiple
variables such as clothing type and quantity, amount of insulating fat on
the victim, environmental humidity or personal dampness such as after
exertion, the circumstances surrounding the hypothermic episode, and so
on. Heat is lost much faster in water, hence the need for wetsuits or dry
suits in cold-weather activities such as kayaking. Water temperatures that
would be quite reasonable as outdoor air temperatures can lead to
hypothermia very quickly. For example, a water temperature of 10 degrees
Celsius (50 F) can be expected to lead to death in approximately 1 hour,
and water temperatures hovering at freezing can lead to death in as little
as 15 minutes. But in water, even a temperature as high as 26 degrees
Celsius (80 F) may, eventually (after many hours) lead to mild
hypothermia.
Alcohol consumption prior to cold exposure may
increase one's risk of becoming hypothermic. Alcohol acts as a
vasodilator, increasing blood flow to the body's extremities, thereby
increasing heat loss. Ironically, this may cause the victim to feel warm
while he or she is rapidly losing heat to the surrounding environment.
Hypothermia is the opposite of
hyperthermia, the condition which causes
heat exhaustion and heat stroke.
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