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Overexposure to heat


Hyperthermia

Hyperthermia is a condition in which the body’s temperature becomes dangerously high. It is generally considered to involve body temperatures of 38°C and above, with direct cell damage occurring at approximately 42°C.

In excessively warm environments, particularly if they are also humid, the body loses heat to the environment less readily. It attempts to compensate by sweating and by increasing circulation to the skin through the dilation of blood vessels close to the surface.  In environmental conditions in which the ambient temperature exceeds that of the skin, the body can only lose heat by sweating.

Factors which disturb the body’s heat balance include:
  • excessive physical exertion
  • high air temperature with high humidity
  • inadequate fluid intake (dehydration)
  • illness (particularly viruses)
  • overly warm enclosed spaces (e.g. an unventilated factory with a tin roof)
  • inappropriately heavy or dark clothing on a hot day
  • some medications (e.g. those for depression, anxiety and Parkinson’s disease)
  • being very old or very young

There are three heat injuries that you may have to manage; heat cramps, heat exhaustion and heat stroke.

Heat cramps
Heat cramps are muscle spasms, the result of the loss of complex salts, which occurs when the body loses more fluid through sweating than is being replaced.

This imbalance of body fluid levels is usually associated with physical exertion such as sporting activities or occupations involving physical labour in warm, often outdoor environments.

Signs and symptoms of heat cramps
  • pale, clammy skin
  • cramping pains in affected area
  • nausea

Management of heat cramps
  • rest the casualty in the shade
  • encourage the casualty to gently stretch the affected muscle
  • apply an ice pack to the affected muscle
  • give the casualty sips of cool water when nausea passes
  • rest and reassure the casualty
  • do not give salt tablets, they will further dehydrate the casualty

Heat exhaustion

Heat exhaustion occurs as a result of salt and fluid loss (through profuse sweating) with increase in blood to the skin and reduced supply to the vital organs.

The increased flow of blood to the skin, and the decrease in total blood volume due to fluid loss, reduces the blood supply to vital organs, which can cause mild shock.

Signs and symptoms of heat exhaustion
  • pale, cold, clammy skin
  • rapid, weak pulse
  • rapid breathing
  • profuse, prolonged sweating
  • thirst
  • nausea
  • vomiting
  • headache (constant)
  • cramps
  • dilated pupils

Management of heat exhaustion
  • lay the casualty down in a cool place
  • loosen or remove excess clothing
  • cool by fanning or sponging with water
  • give cool water to drink, if conscious, in small sips
  • rest and reassure the casualty
  • monitor and record vital signs
  • seek medical aid - call Triple Zero (000) for an ambulance if you are concerned about the casualty or if the casualty vomits or does not recover promptly