Friday, 15 June 2007

Hypothermia and paradoxical undressing

The temperature of our body is normally around 37ºC… however, it is only necessary a 2º decrease for hypothermia to initiate… As body temperature decreases even more the consequences become more and more negative, so that between 25 and 28ºC the heart just stops and dead is the logical outcome...

Considering that hypothermia is caused by a decrease in body temperature, how to explain that so many people are found dead due to this condition and yet with no clothes on? As this scenario was very often observed in poor people in cities, the logical explanation was raping and theft. Yet this doesn’t explain why victims of hypothermia refuse warming clothes when rescued… Overall, this phenomenon is commonly referred to as ‘paradoxical undressing’…

How to explain this apparently contradictory behaviour? A quite logical theory tries to give an explanation. When hypothermia initiates, the organism tries to prevent vital organs from cooling too much, and as a consequence the ‘available’ heat is concentrated to central areas of the body. This is possible by reducing peripheral circulation, namely by contraction of blood vessels. Vasoconstriction, possible by contraction of those muscles situated around blood vessels, requires energy, namely glucose provided by circulation itself.

Vasodilation, on the other hand, doesn’t require energy. Therefore, after a period of stress as that of hypothermia, with reduced income of energy and accumulated tiredness, the muscles lining the vessels tend to relax and allow once again the flow of blood into the restricted areas of the blody. The sudden flow of blood kept warm by its concentration elsewhere is thought to be responsible by the sudden sensation of warmth which leads hypothermia victims to undress. Obviously, the undressing turns out to help the hipothermial process, and victims eventually die. In fact, there is no register so far of any hypothermia victim able to survive without help after reaching the ‘paradoxical undressing’ state.

To finish off it is interesting to note that in 20% of the lethal cases of hypothermia another perhaps not so strange situation is registered, the so called ‘hide-and-die’ syndrome, which leads to the finding of hypothermia victims hiding in the most unlogical places, namely under beds of behind closets. This is probably the remains of an old instinct that seems to be present in a variety of animals and can basically be translated into the following piece of wisdom- ‘when things get really bad, find somewhere to hide’. I wonder if this works with the exams too… :-)


Based on ‘Paradoxical undressing; 21st April 2007, pag 50, New Scientist

6 comments:

James Lloyd said...

the theory seems to assume that blood will flow to all parts if the body at the same time, ie the glucose store runs out across the body at the same time. do all muscles in leg and the arms have the same relative muscle to mass ratio? probably but just wondered.
also why do the victims still not want cloths? how long is it after the reentry of blood into the periphery does it take to cool down again? not long i would assume, maybe long enough to make someone take their cloths off but i think soon after they would want them back on.

Menelaos Symeonides said...

How strange, I've never heard of this before.

James, if they die of hypothermia by the time they realise they are cold, then they won't get a chance to want their clothes back on...

James Lloyd said...

yes i agree. this is all assuming that those people who want stay naked were found in the short space of time of not feeling cold, probably. i was just wondering.

Catarina Vicente said...

that is what I was going to argue, but i guess melly was faster :)

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