Symptoms in Detail

Symptoms in Detail

A more in depth look at the reasons for the symptoms of hypothermia

Symptoms in Detail 


The symptoms of hypothermia are the body’s way of trying to make physical changes that lead to it being able to keep warm, with the obvious one being shivering, where the body tries to generate heat through rapid muscle movement.  Shivering is at the low end of the scale of seriousness, and is well known to be associated with being cold. Other mild symptoms include rapid breathing, fast heart rate but weak pulse, mild mental confusion as the brain function decreases, increased urination and high blood pressure, although the latter is hard to detect on the hill.


When the temperature of the core starts to fall, and shivering isn’t yielding the desired results, the body performs a neat trick called vasoconstriction, which basically means that it severely restricts the flow of warm blood to the extremities of the body, as the warm blood is needed to keep the organs working. Think of vasoconstriction as being like a tap at the point of each limb joining the torso. The tap is normally fully open, but when the core starts to cool, the taps are slowly turned off. The same can be said for the skin, in that blood flow to the skin is also restricted, as it’s not important for keeping the core warm.  These are two important symptoms of hypothermia; grey or ashen looking skin, and cold limbs that become more difficult to move due to lack of blood.  When skin becomes cold, it’s because the taps are turned off.  Blurred vision is also a common sign of the onset of hypothermia.


As the core cools further, shivering can become more violent, movement over the ground will become slower and the subject can become more confused. The skin will continue to cool as vasoconstriction continues and the skin temperature becomes more regulated by the external environment rather than blood heating it.  Extremities of skin, such as lips, ears, fingers and toes can turn blue.  (Although, I can’t see a situation where I would be recommend removal of footwear to check toes colour!)  Windchill can be a significant factor – read more here.


If heat is not restored to the body the symptoms will progress, leading to a severe case of hypothermia. Simple movement of hands and feet can become almost impossible with walking itself almost impossible.  Previously fast pulse and breathing rates will slow down considerably and the subject can become forgetful (amnesia).  Speech can become slurred, combined with possibly being incoherent and exhibiting irrational and possibly aggressive behaviour.  In 20% to 50% of deaths from hypothermia, the subject exhibits what’s known as paradoxical undressing.  This is where they get a sudden burst of energy and remove clothing or refuse offered warmth from others.  There is no explanation for paradoxical undressing, but there is some thought that perhaps blood rushes to the skin making the casualty feel very warm. The final stages of hypothermia could include terminal burrowing, where the subject tries to hide in a small space, as the body’s penultimate attempt to find warmth, followed by coma, and death.