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Effects of heat and cold on the human body

 

F

C

 

 

Heat
Stroke

109.4

43

Unconscious, fits, confusion, restless,  headache, dizzy, strong bounding pulse, hot to touch, flushed dry skin

107.6

42

105.8

41

104

40

 

Heat
Exhaustion

102.4

39

Cramping in stomach, arms, and legs. Pale sweaty skin, nausea, loss of appetite

100.4

38

Normal

98.6

37

Normal body temperature

96.8

36

 

Mild hypothermia

95

35

Shivering

93.2

34

Slurred speech, confusion

 

91.4

 

33

Shivering stops, muscles rigid, slow weak pulse

89.6

32

drowsiness

 

Severe Hypothermia

87.9

31

Response levels low

86

30

Unconscious, dilated pupils

84.2

29

No detectable pulse

82.4

28

Appearance of death

80.6

27

78.8

26

DEATH

Hypothermia

This occurs when the body’s core temperature drops below 35 degrees C. If the core body temperature falls below 26 degrees C then death is likely, but not always certain as in certain conditions the extreme cold can help preserve life and people have been resuscitated with body temperatures as low as 10 degrees C.  In an outdoors situation there are two main risk factors.

Alcohol consumption will also increase risk of hypothermia, as despite an initial feeling of warmth the alcohol dilates blood vessels so warm blood from the body core rushes to the skin (hence the flushed appearance and perceived warmth) this warm core blood then quickly cools as it is near the surface of the skin and is returned to the core much cooler which lowers core body temperature much quicker.

The possible signs of hypothermia are shown in the table above but key symptoms include

Someone who falls unconscious needs urgent medical attention, while waiting for this to arrive try not to move the casualty and insulate as well as possible including underneath if in an exposed location, a survival bag is ideal for this as it will provide protection vs wind and rain.

If the causality nis still conscious insulate as well as possible and shelter from exposure to wind and rain. If you have spare warm dry garments then replace any wet clothes with these, if warm dry clothing is not available do not remove clothing but insulate the causality.

DO NOT place casualty near direct sources of heat as this can reduce blood pressure and stress the heart.

Frostbite

Frostbite is a very dangerous condition caused when extreme cold freezes the cells in a limb, normally the fingertips and/or toes/ tips of ears.  Ice crystals form in the cells which then die. As expected Hypothermia is common is those who have frostbite which can result in the death of a limb or more commonly the loss of fingers and toes. In extreme conditions the symptoms can be hard to spot at first and there are many stories of people removing wet cold boots to find they have lost several toes.

Normal warning signs include;

Hospital treat is key but if this is going to be some time in coming, try to remove any rings or watches as these may cut into the skin as the skin swells and freezes. Your next priority is to stop the limb freezing so get the casualty to place their affected limb under their arm if possible for warmth or warm it in your hands. Remove any cold wet gloves / socks etc and replace with dry ones if possible. If the limb is likely to refreeze don’t warm it and thawing and refreezing will cause more damage.

Heat Exhaustion

Heat exhaustion is caused by the body loosing water and essential salts due to sweating in an attempt to cool the body down. It occurs when the core temperature goes above 38 degrees C, and can come on rapidly due to hot dry conditions or physical exertion in such conditions. If not treated it is likely to lead to heat stroke which is a more dangerous condition

Symptoms are listed in the table but can include;

You should always seek medical advice and request urgent medical attention if their response levels start to drop.  You should also take the affected person to a cool place, and get them to lie down. Re hydrate them using water and if available isotonic drinks or oral re-hydration solutions which are useful item to include in any first aid kit. If untreated this condition can develop into Heat Stroke which is life threatening

Heat Stroke

Heat stroke is life threatening condition caused by the sweating response in the body failing to keep the core temperature down. This results in the failure of the hypothalamus (the part of the brain which controls temperature) this means that the core body temperature can rise to dangerous levels (over 40 degrees C) within a relatively short period of time (as little as 10 minutes). Symptoms are listed in the table but can also include

This requires urgent medical attention, while waiting for help to arrive you need to cool the casualty as quickly as possible in what ever way you can. Examples of this include

With all cases seek urgent medical assistance, even if the casualty seems to recover