Heatstroke is caused by excessive fluid and salt loss in hot or humid conditions, this leads to general dehydration and exhaustion. Predisposing factors include general fatigue or ill health, too much alcohol, and wearing too many clothes. As heatstroke develops the person complains of feeling hot, headachy, dizzy and nauseous, and begins to breathe fast and noisily; the skin remains dry, although the face may be flushed, there may be cramps or muscle twitches. If temperature is allowed to rise above 40°C (104°F), the person eventually collapses and becomes unconscious.
First aid priorities are to bring the person’s temperature down and prevent further dehydration. Undress the person, wrap him or her in a wet sheet, and create a draught by fanning or switching on an electric fan; as the water in the sheet evaporates, it will cool the skin beneath. Keep the sheet well wetted. Sponge the face. Give only water to drink, with a little salt dissolved in it (1/2 teaspoon of salt to 0.5 litre [1 pint] water – these quantities are important as too much salt will cause vomiting and further dehydration).
Once the person has cooled down, cover them with a dry sheet. If temperature starts to climb again, Dial 911.