A rectal temperature over 40°C (104°F) after exposure to a hot environment.
Confusion, severe restlessness, aggressive behaviour or anxiety.
Fast heart rate.
Sweating that may be heavy or may have stopped.
Skin that may be red, pale, hot, and dry, even in the armpits.
Severe vomiting and diarrhea.
Heatstroke is a medical emergency. Even with immediate treatment, it can be life-threatening or result in serious, long-term complications. After calling 911 or other emergency medical services, follow these first aid steps.
Move the person into a cool place, out of direct sunlight.
Remove the person's unnecessary clothing, and place the person on his or her side to expose as much skin surface to the air as possible.
Cool the person's entire body by sponging or spraying cold water, and fan the person to help lower the person's body temperature. Watch for signs of rapidly progressing heatstroke, such as seizure, unconsciousness for longer than a few seconds, and moderate to severe difficulty breathing.
Do not give aspirin or acetaminophen to reduce a high body temperature that can occur with heatstroke. These medicines may cause problems because of the body's response to heatstroke.
If the person is awake and alert enough to swallow, give the person fluids [1 L (32 fl oz) to 2 L (64 fl oz) over 1 to 2 hours] for hydration. You may have to help. Make sure the person is sitting up enough so that he or she does not choke. Most people with heatstroke have an altered level of consciousness and cannot safely be given fluids to drink.
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