Heat stroke (also called sun stroke) is a life-threatening medical condition that occurs when the body's cooling system stops working and the body’s core temperature increases to a point at which brain damage or damage to internal organs can occur (105° F [40.5° C] or greater).
Sweating is how the body normally cools itself, but under some conditions, sweating isn’t enough and the body’s temperature control system becomes overloaded. When this happens, the body temperature rises rapidly. Very high body temperatures can cause brain damage or damage to other vital organs.
Heat stroke is a medical emergency that can lead to death if it is not treated promptly. Get to a hospital’s emergency department right away (do not drive yourself) if heat stroke is suspected or if the following symptoms occur:
- Inability to keep fluids down (vomiting)
- Deterioration of mental status (confusion or delirium)
- Shortness of breath
- Abdominal pain
- Chest pain
Symptoms of heat stroke include:
- Body temperature of 104°F (40°C) or higher
- Skin redness (flushing) and warmth or heat
- Fast breathing (hyperventilation)
- Fast heartbeat
- Brain symptoms
- Dry skin
- Vomiting
- Diarrhea
- Muscle cramps
- Weakness
- Headaches
- Absence of sweating due to dehydration
- Changes in blood pressure (may be high or low)
What Causes Heat Stroke?
Heat stroke occurs when heat exhaustion – a condition that precedes heat stroke – is not promptly treated. Heat stroke is a medical emergency that can lead to death if it is not treated right away.
Heat stroke is usually caused by exercising, working, or playing in very hot and humid weather. Insufficient fluid intake, wearing excess layers of clothing, and alcohol consumption can also contribute to the development of heat stroke.
Heat stroke can also be caused by prolonged exposure to very hot and humid environments, even without activity. This happens more often in the elderly or people with underlying medical conditions.
Risk factors that can make people more likely to develop heat stroke include:
- Inadequate fluid intake
- Diuretic use
- Alcohol use
- Low potassium levels (hypokalemia)
- Inadequate heat acclimatization
- Age (toddlers and young children, the elderly)
- Being overweight or obese
- Low fitness levels
- Lack of sleep
- Stomach illness
How Is Heat Stroke Diagnosed?
Heat stroke is diagnosed with a patient history, physical examination, and a temperature reading. Other tests used to determine if the heat stroke has affected other organs in in the body may include:
- Blood tests
- Urine tests
- Chest X-ray
- Electrocardiogram (ECG) of the heart
What Is the Treatment for Heat Stroke?
Heat stroke is a medical emergency. There is no home treatment for heat stroke.
Heat stroke must be treated medically and treatment involves cooling the body as soon as possible. Methods used to reduce a person’s body temperature may include:
- Evaporative techniques, such as using a fan to blow air on wet skin
- Immersion techniques, such as placing the patient into an ice bath
- Invasive cooling techniques, such as chilled intravenous (IV) fluids
- Ice packs applied to the body or cooling blankets may be used in addition to the methods above
Treatment continues until the patient’s core body temperature is 101.3°-102.2° F (38.5°-39° C).
Patients with heat stroke will be hospitalized for further testing and treatment.
From 
Healthy Resources
https://www.uptodate.com/contents/heat-stroke-the-basics?search=Heat%20Stroke&source=search_result&selectedTitle=1~66&usage_type=default&display_rank=1
https://emedicine.medscape.com/article/166320-overview
https://ksi.uconn.edu/emergency-conditions/heat-illnesses/exertional-heat-stroke/heat-stroke-risk-factors/#
https://www.cdc.gov/disasters/extremeheat/faq.html