Heat Exhaustion and Heatstroke

Conditions resulting from exposure to excessive heat, in which there is loss of fluids and a rise in body temperature

  • May occur at any age but most common in babies and elderly people
  • Exertion in a hot environment is a risk factor
  • Gender and genetics are not significant factors

In a hot environment, the body loses heat by diverting blood to the skin and by sweating. Profuse sweating may lead to an excessive loss of fluids and salts, resulting in heat exhaustion. This condition is rarely serious, but, if exposure to heat continues, heatstroke may occur as the body’s normal cooling mechanisms break down and the temperature of the body rises. Heatstroke is a life-threatening medical emergency.

Heat exhaustion and heatstroke most commonly occur above 40°C (104°F). High humidity levels increase the risk of heatstroke because sweating is ineffective and heat loss is decreased.

Who is at risk?

Heat exhaustion and heatstroke may affect otherwise healthy people, particularly after physical exertion in a hot climate. People who come from temperate climates and travel to the tropics need time to acclimatize to the heat before they can safely exert themselves.

The body’s cooling mechanisms are less efficient in infants and in elderly people, making them more susceptible to heat exhaustion and heatstroke. Diabetes mellitus, obesity, alcohol dependence, and chronic heart failure all reduce the body’s ability to lose heat. Diarrhoea may contribute to dehydration and increase the risk of developing heat exhaustion and heatstroke.

What are the symptoms?

After prolonged exposure to hot conditions, the following symptoms of heat exhaustion may develop:

  • Profuse sweating.

  • Tiredness.

  • Muscle cramps.

  • Nausea and vomiting.

  • Faintness and unsteadiness.

  • Headache.

If exposure to heat continues, the body temperature rises and heatstroke may develop, causing symptoms such as:

  • Fast, shallow breathing.

  • Confusion and disorientation.

  • Seizures.

Left untreated, heatstroke may progress to coma in minutes. Death may be due to kidney failure, acute heart failure, or direct heat-induced damage to the brain.

What can I do?

Heat exhaustion can be treated easily. The affected person should rest in a cool place (ideally in an air-conditioned building) and drink plenty of fluids (water or a rehydration drink, such as an electrolyte sports drink) until he or she feels comfortable. Alcohol and caffeine should be avoided. If heatstroke is suspected, he or she should be admitted to hospital as soon as possible.

What might the doctor do?

Treatment for heatstroke is usually carried out in an intensive therapy unit. Body temperature is lowered by sponging the body with tepid water or loosely wrapping the person in a wet sheet and placing him or her near a fan. Intravenous fluids are given. Once the body temperature has been reduced to 38°C (100°F), these cooling procedures are stopped to prevent the development of hypothermia. Monitoring is carried out continuously to make sure that the body temperature is returning to normal levels and that vital organs are functioning normally. In some severe cases, mechanical ventilation may be required to assist breathing.

Most people with heat exhaustion recover in a few hours if they are moved to a cooler place and fluids are gradually replaced. If heatstroke is treated promptly, most people recover after a few days of bed rest, although their body temperature may fluctuate for several weeks afterwards.

Can they be prevented?

Heat-related disorders can be largely prevented by avoiding strenuous exertion in the heat of the day, spending as much time as possible in the shade, consuming large quantities of liquids, and avoiding alcoholic drinks.

The risk of heatstroke

As the amount of moisture in the atmosphere (the relative humidity) increases, it becomes more and more difficult to lose heat from the body by sweating, and heatstroke may therefore occur at lower air temperatures.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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