Hypothermia: Can you “Bear” the cold?

Every body’s metabolism requires an optimal temperature for efficient operation: cars, cactus, lizards, bears and even human beings.  Metabolism refers to biochemical change and secondarily to the speed at which that change occurs.   The speed of biochemical change is referred to as the “basal metabolic rate” or BMR.

Just like ice, molasses and butter, when the temperature rises, movement increases.  Conversely when temperature falls, all molecules (tiny atoms) slowdown in their vibration.  With too slow a molecular vibration, everything freezes.

The blood’s circulation, the journey from heart to body cells and back again, is faster when we are warm and slower when we are cold.  The Bear takes advantage of BMR speed principles when he hibernates in winter.  The Bear’s goal is to slow down his circulation and other biochemical processes to use less fuel, since food as bodily fuel, is less available in winter than summertime.  All bodily processes require fuel as food to continue to function.  When the Bear hibernates all of his bodily functions slow down: heart rate, digestion and respiration.  Even brain function slows down.  As the Bear enters his wintery hibernation state he puts his body into a form of Hypothermia.

“Hypothermia” is a state of lowered body temperature: hypo (below) thermia (temperature).   Cellular Hypothermia can be caused by both internal and external mechanisms.  In the center of our brain is an organ called the Hypothalamus.  It is “below” (hypo) the Thalamus.  Of the many functions for which the Hypothalamus is responsible temperature control is included.  It is also thought to be a type of internal “biological clock” regulating the body’s daily rhythms.  For example it can slow the BMR at night when we sleep, which includes lowering the body temperature.

The Hypothalamus attempts to keep the body within a temperature range of 97 to 99 degrees Fahrenheit.  If the body’s core temperature falls to 95 degrees or below then it begins to manifest symptoms of Hypothermia.

Perhaps you remember the 1908 story by author Jack London “To Build a Fire” in which the hero and his Husky dog are faced with freezing outdoor temperatures in the Yukon Territory of Canada.  The hero unable to build a fire, becomes sleepy as his body temperature falls.

“… Well, he was bound to freeze anyway, and he might as well take it decently. With this new-found peace of mind came the first glimmerings of drowsiness. A good idea, he thought, to sleep off to death. It was like taking an anesthetic. Freezing was not so bad as people thought. There were lots worse ways to die.”

Hypothermia has three phases.  The body attempts to preserve vital functions while shutting down those less needed for survival.  If hypothermia progresses without interruption it can lead to death.  In the Jack London story, the hero is entering phase three.

Phase One:  Shivering occurs.  Shivering is a rapid contraction and relaxation of small muscles to generate warmth.  Blood vessels in the hands and feet constrict (vasoconstriction) to maintain better blood flow to the vital internal organs like Heart and Liver.  There may be a numbing or tingling sensation in the hands and feet.  Muscle dexterity is impaired.  Breathing and heart rate slow.

Phase Two:  Shivering becomes violent.  Movements are uncoordinated.  Exposed skin turns blue (cyanosis) from poor blood circulation.  Mental confusion follows.  Body core temperature has fallen below 90 degrees.

Phase Three:  If body core temperature falls below 82 degrees the final phase is entered.  Shivering stops and cellular metabolism starts to shut down.  Exposed tissue becomes puffy as well as blue.  In “Frostbite” the tissue has frozen and begun cellular destruction.  Brain function slows and the person falls into a coma.  Heart rate may speed momentarily before slowing completely.

Physicians have learned to utilize the natural survival properties of Hypothermia to treat head injury.  To decrease the demands on the brain in order to allow it to rest and thus heal, a physician may decide to place the patient into artificial Hypothermia.  This can be done several ways, by lowered external temperature, by injections of insulin to create a diabetic-type induced coma or by sleep medications such as barbiturates.  The duration and degree of Hypothermia is controlled and closely monitored by the physician.

Exposure to cold in the elements does not allow for the same type of medical control.  For optimum bodily function the phases of Hypothermia are to be avoided.  In winter with subfreezing temperatures, below 32 degrees Fahrenheit or 0 degrees Celsius, this becomes more challenging to do.  Layering clothing allows air to be trapped and warmed by body heat.  This is what the bird does when he fluffs and puffs his feathers to stay warm.  Not having feathers or fur it is in our best interest to choose clothing made from fibers that can provide similar insulation from the cold: silk, wool or synthetics like polyester.  Cotton and linen lack this insulation quality.  Cover all exposed skin surfaces – heads, necks and hands with caps, scarves and mittens.   Insulation is especially important with children and the elderly.  A thin layer of silk, followed by wool layers then a tightly woven polyester jacket which both insulates and blocks the wind would be ideal.

Early signs of Hypothermia would be shivering, bluish extremities (hands, toes, nose, ears, lips, etc.) and a numb or tingling sensation in the hands or feet.  Seek medical attention for signs of moderate Hypothermia (phase two and three).  Bundle up the patients in layers.  Remove them from any wind or watery exposure which can also cause heat loss.  Remove and replace any wet clothing.  The patient can assume the “heat escape lessening position” with knees bent and legs drawn up into the chest and arms around the legs holding the legs in or arms across the chest.  If more heat is desired bundle the patient together with another person.  This is also the best approach to warming an infant, bundle the infant with the mother whose body warmth will heat the child.  A skin to skin infant contact with the mother is preferred.

If the patient is alert warm sweet liquids can be provided.  Dehydration is a side effect from the vasoconstriction of Hypothermia.  Avoid alcohol or caffeine drinks which can complicate the recovery.  Place the patient in a warm, not hot, bath to gradually rewarm them and dry quickly when rewarmed.  And next time we will leave the hibernation hypothermia to the Bears, they have the fur coats to bare it.