• Heatstroke is a medical emergency that occurs in hot, humid conditions. Core body temperature rises to 41°C .
  • Signs of heatstroke include: confusion; irritability; rapid pulse; hot, dry, red skin.
  • First aid involves cooling the person down and hydration.
  • Heat exhaustion involves an excessive drop in blood pressure following exercise. Core body temperature rises to 38-40°C .

What is heatstroke and what causes it?
Heatstroke occurs in hot, humid conditions when the body fails to control its own temperature. It is a medical emergency. A significant number of cases are seen each year during the summer months in South Africa when temperatures of 28°C and higher, and humidity above 70%, are reached.

There are two types of heatstroke: classical and exercise-induced. Classical heatstroke affects the more fragile - the very young and the elderly, often those with heart disease. It occurs without any exercise activity during a heat wave. Young children left in a hot car are particularly at risk. There is usually no sweating.

Exercise-induced heatstroke is more common in young, healthy, fit athletes who exercise in hot, and especially humid, conditions. Athletes who exercise vigorously for short periods, such as in short-distance races (6-15 km), rather than marathons, are most at risk. It seems that only certain athletes are susceptible to this condition, suggesting an inherited metabolic predisposition.

What are the symptoms and signs of heatstroke?
The hallmark of this condition is an extremely high body core temperature of at least 41° C (taken rectally) and a reduced level of consciousness. The person initially becomes irritable and confused and may have seizures. Other early symptoms include weakness, headache, nausea and vomiting, and muscular pain. The pulse is rapid and the skin hot, red and dry, even under the armpits. If the condition is not promptly treated, the person becomes unconscious and might die.

Heatstroke is deadly and it is crucial it is recognised early and immediate first aid and medical treatment given.

First aid for heatstroke

Get immediate medical help. While waiting for an ambulance or transport to hospital:

  • Move the person to a cool, shaded area and check the ABCs (airway, breathing, circulation).
  • Apply ice packs or cover the person with cool, wet sheets. The sooner the person is cooled, the lower the risk of mortality.
  • If the person is able to drink, give them water or a sports drink.

Hospitalisation is always necessary as temperature could increase again after cooling.

Can heat stroke be prevented?

Help prevent heatstroke by:

  • Avoiding strenuous physical activity outdoors during the hottest hours of the day ( 10 am to 3 pm). Avoid overexposure to the sun.
  • Staying cool. Wear light clothes and a wide-brimmed hat and take a cool bath or shower once or twice a day.
  • Staying well hydrated - but be careful not to over-hydrate.

What is heat exhaustion and what causes it?
Heat exhaustion occurs when there is an excessive drop in blood pressure as a result of the pooling of blood in the lower limbs, following exercise. Despite its name, heat exhaustion is not directly related to heat and is no longer considered the first step towards the development of heatstroke.

What are the symptoms and signs of heat exhaustion?
Suspect heat exhaustion when a person who has stopped exercising on a hot day, suddenly becomes listless, weak and dizzy. The pulse is rapid and there may be nausea and vomiting. Unlike heatstroke, the body core temperature rises to over 38°C , but never exceeds 40°C , and mental status and behaviour are normal.

First aid for heat exhaustion

  • Lay the person on his back and elevate his legs and pelvis.
  • Encourage him to drink, even if he is not thirsty.
  • Following basic first aid management, recovery is usually rapid.

Last updated: July 2009

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