Six Degrees of Hypothermia

blizzard

On December 23, 2010, a 7-year-old girl fell into a lake outside Orest, Sweden.  No one knows what the temperature of the lake was.  But it was very, very cold.  When pulled from the lake, the girl had a body temperature of 55 degrees Fahrenheit.

Much of the United States is currently in the throes of a winter deep freeze, with wind chills reaching at least 30 degrees below zero in many highly populated  areas of the Midwest.  Hopefully there will be few if any fatalities.  But this is serious and dangerous weather.

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I am just going outside, and may be some time (Capt. Lawrence “Titus” Oates , of Robert Falcon Scott‘s South Pole expeditionary force, as he walked into a blizzard to his death on March 16, 1912)

Each person’s body insulates itself differently.  Fatty tissue, muscle, age, and internal organ health influence how soon the body’s heart and brain will shut down from what’s known as “hypothermia.”  Mental condition also plays a part.  Buddhist monks in Tibet use meditation to raise the temperature of their extremities as much as 15 degrees Fahrenheit.  But every body goes through specific stages of progression to and during hypothermia, or “subnormal body temperature,” before death occurs.

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Doomed 1912 Scott Expedition to South Pole (Oates is back left, Scott is back center)

100.8 degrees:  When one feels cold, body exertion is the logical way to heat up.  One can raise one’s core temperature to 100.8 degrees through exercise.  When I go for a run in the winter, I like to feel a little chill at the start, since I know I’ll be snug and warm after about 5 minutes of running.

98.6 degrees:  But exercise also dilates the capillaries, which transport this excess heat to the skin, then to be expelled from the body.  This is exacerbated by wet clothing.  Body temperature then drops back to the normal 98.6… then lower.

95 degrees:  At 97 degrees, neck and shoulder muscles constrict in what’s known as “pre-shivering muscle tone.”  The brain’s hypothalamus has been signaled to constrict all surface capillaries, sending warm blood to the internal organs but pulling heat away from hands and feet.  At 95 degrees, the muscles contract, causing the body to shake uncontrollably in an effort to preserve warmth.  This is considered mild hypothermia.  Many of us have experienced this state at one time or another.

93 degrees:  Now it gets serious.  Core body heat declines rapidly, with the head alone releasing 50 percent of the heat.  Amnesia sets in, because for every one-degree drop in body temperature, cerebral metabolic rate also drops by 3 to 5 percent.

90 degrees:  Severe hypothermia.  At this point a victim falls into a drug-like stupor.  Below 90, the shivering stops, because the body’s automatic heat-generation system gives up.

86 degrees:  The heart becomes arrhythmic and pumps less than two-thirds the normal concentration of blood.  Due to the brain’s continued metabolic apathy, hallucinations occur.

Below 85 degrees:  At this most extreme stage of hypothermia, people have been known to rouse from their stupor and tear off their clothes due to feelings of intense heat.  The phenomenon is known as “paradoxical undressing.”  Scientists believe this may be the result of constricted blood vessels near the skin that suddenly becoming dilated, causing a severe burning sensation.

There is no exact temperature at which the human body “dies” from cold.  Numerous people have recovered from extreme hypothermia if rescued in time.  Extreme coldness slows the brain’s metabolism, so it needs much less oxygen to survive than when warm.  In many cases, the only long-term consequence of extreme hypothermia is frostbite (the freezing and destruction of tissue), which might, at most, require amputation of fingers or toes.  But this assumes the victim receives immediate medical treatment.

The little Swedish girl miraculously survived.  She was pulled from the brink of death by a combination of slow heating and a heart-and-lung machine.  Her doctor also attributed her survival to her young and developing brain.  Her body temperature of 55 degrees Fahrenheit was the lowest ever recorded for a living human being.

NOTE:  Much of the information here is derived from the chapter “As Freezing Persons Recollect the Snow: Hypothermia” from the book LAST BREATH: THE LIMITS OF ADVENTURE by author and Outside Magazine correspondent Peter Stark.

hiker

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