Hypothermia Causes

Normal body temperature is the reflection of a delicate balance between heat production and heat loss. Many of the chemical reactions necessary for human survival can occur only in specific temperature ranges. The human brain has a number of ways to maintain vital temperature. When these mechanisms are overwhelmed, heat loss happens faster than heat production resulting in hypothermia.

Sometimes the body’s temperature control can be altered by disease. In this case, core body temperature can decrease in almost any environment. This condition is called secondary hypothermia.

• The body loses heat in several ways.
  
  
  • 55-65% is lost to the environment via radiation.
    
    
  • Conduction only accounts for 2-3% in dry conditions, but this figure can increase to 50% if the victim is immersed in cold water.
    
    
  • Convection accounts for 10%, while 2-9% is lost to heating inspired air.
    
    
  • 20-27% is lost as a result of evaporation from the skin and lungs.
    
    
  • Children cool quicker than adults because they have more surface area compared to body mass.
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• The body also has a variety of methods to increase heat production. But at a certain low level, the body cannot continue heat production, and core body temperature drops quickly. From 98.6°F to 89.6°F, the body begins to shiver, blood vessels contract, and hormones generate heat.
  
  
  • Shivering can double heat generation. However, this can only last a few hours. Eventually fatigue sets in, and the body exhausts its fuel stores.
    
    
  • Blood vessels contract or narrow in your arms and legs, which allows warm blood to remain internal and somewhat protected from the cold temperatures to which the skin is subjected.
    
    
  • Hormones and other small proteins are released in order to speed up the basal metabolic rate, essentially eating stored fuels in the hopes of producing heat as a byproduct.
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• From 89.6°F to 75.2°F, shivering stops, and basic metabolism progressively slows down. At a body temperature lower than 75.2°F, almost every mechanism for heat conservation becomes inactive. Core body temperature continues to plummet. In primary hypothermia, the body is unable to generate heat fast enough to compensate for ongoing heat losses. This primarily is a disease of exposure.
  
  
  • In general, in cold, dry environments, hypothermia occurs over a period of hours.
    
    
  • In cold water, core temperature can drop to dangerous levels in a matter of minutes.
    
    
  • The elderly, because of their impaired ability to produce and retain heat, may become hypothermic over a period of days while living in indoor, regulated conditions that other people would find comfortable.
    
    
  • The homeless, alcoholics, and mentally ill are prone to hypothermia because they are unable to find adequate shelter or are unable to recognize when it is time to come in from the cold.
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• In secondary hypothermia, something goes wrong with the body’s heat-balancing mechanisms. People with such diseases as stroke, spinal cord injury, low blood sugar, and a variety of skin disorders can become hypothermic in only mildly cool air.