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Heat Stroke: Causes, Symptoms, Treatments and Prevention

Heat stroke is a potentially life-threatening condition where there is a failure of temperature regulation in the body.  The overheating of the body leads to a core body temperature of >40° C (104° F) along with other bodily changes ultimately affecting the brain and leading to coma.

heat sroke

Most cases of heat stroke occur in young subjects exercising in the sun (such as athletes and military recruits) or in elderly or sick patients during heat stress.

In India, when the temperature soars during summer seasons, heat strokes are reported in many parts of the country and in those who are homeless and working outdoors under the hot sun.

Heat stroke causes and risk factors


Classic heat stroke (non-exertional heat stroke) occurs as a result of exposure to the hot environment. It usually happens during summer months when there is high temperature and humidity. Those at risk include unsheltered people, those living in poorly ventilated homes, older individuals who do not drink enough water, and chronically ill patients who are taking medications that contribute to heat stress.

heat stoke, beware of the sun

Exertional heat stroke occurs when the elevated body temperature is caused by the internal heat load generated through intense physical activity (exercising or working) in hot weather and humidity. It is commonly seen in young healthy athletic individuals. It can develop at a rapid rate and because of disturbance in the heat-regulating mechanisms.

Risk factors

The risk factors for heat stroke include

  • Increased heat production – Fever, Exercise, Thyrotoxicosis
  • Reduced heat loss from the body- Hot weather, humidity, lack of acclimatisation, dehydration and Low potassium levels (hypokalemia).
  • Ingestion of some medications – Anti-cholinergic medicines, phenothiazines, barbiturates, etc.
  • Debilitating conditions- Skin diseases, cystic fibrosis, brain injuries, old age etc.

Heat stroke symptoms

Heat stroke can develop quickly over a few minutes or gradually over many hours or days.

The symptoms of heat stroke include

• Fatigue and weakness

• Feeling faint or dizzy

• Headache

• The skin may be dry and hot in classic heat stroke. In exertional heat stroke, sweating may be present and skin may be moist

• Muscle weakness and cramps

• Nausea and vomiting

• Rapid heart beat

• Fast breathing

• Changed mental state or behaviour such as confusion, disorientation, agitation, slurred speech, seizures, unconsciousness and coma.

The main sign of heatstroke is the elevation of body temperature to 40°C (104° F) or higher.

Heat stroke diagnosis

Doctors diagnose heat stroke based on the symptoms.

Measurement of core body temperature using a thermometer placed in the mouth, groin folds or armpits and recording a temperature of 40°C (104° F) is the main sign for diagnosis.

A few laboratory tests may be ordered to confirm the diagnosis, look for complications and rule out other causes:

  •  Electrolytes: Such as sodium and potassium levels in the blood
  • Urine examination: A routine examination of urine may be done
  • Liver and kidney function tests
  • Creatine kinase test to detect rhabdomyolysis (muscle damage)
  • Routine blood tests to look for anaemia, diabetes, etc.
  • ECG – to check for heart activity
  • Chest X-ray – To check for aspiration of fluids and oedema in lungs
  • CT and MRI scans may be done to look for damage to internal organs

Heat stroke treatment and prevention

First aid

If someone is showing the signs of exhaustion due to heat, you should:

  • Make the person lay down in a cool location- someplace in shade or a room with air conditioning.
  • Remove any unwanted clothing and expose as much skin as possible.
  • Cool the skin using a wet cloth or sponge, or cold packs on the neck, armpits and other exposed parts of the body. Fan the person with a cloth or newspaper when the skin is moist.
  • Make the person drink fluids such as water, fruit juice, oral rehydration fluid (ORS).
  • If the person is having fits (seizures), remove objects around the person to avoid injury.
  • Remain with the person till they are feeling better.

Most people should recover within 30 minutes. If they do not recover within 30 minutes, or if they are having severe symptoms such as loss of consciousness, confusion, or fits, then call for emergency medical help.


The aim of therapy is to cool the body to a normal temperature and prevent damage to vital organs.

  • Cold-water bath: Your doctor may give you a bath with cold or ice water to rapidly bring down your temperature.
  • Ice packs and cooling blankets: The other method is to wrap you in ice packs or a cooling blanket.
  • Fanning: Cool water is applied on the skin and air is fanned, which makes the water evaporate and cool the skin.
  • Medications to prevent shivering: Methods used to make you cold may cause you to shiver. This compensatory mechanism of the body may increase the body temperature again. Medications may be given to prevent this compensatory shivering and hence a rebound increase in the body temperature.


  • Check for heatwave warnings on newspapers and TV and stay indoors when there is a potential danger
  • Avoid the outdoors when the sun is beating down hard between 11 am to 3 pm.
  • Wear weather appropriate clothes. In summer wear loose fitting and light colour clothes.
  • Avoid extreme physical activities in hot weather.
  • Drink plenty of liquids, preferably cold drinks. Avoid caffeine, hot drinks and excess alcohol.
  • Eat food substances that contain high fluid content such as cucumber, tomato, orange, watermelon, etc.
  •  You can keep yourself cool by using a damp cloth on the back of your neck, or sprinkling water over your skin or clothes.
  • If your urination frequency is decreased or if the urine is dark, it indicates that you are dehydrated and need to drink more liquids.
  • Keep your indoors cool by keeping the windows and door closed or covered with curtains, to prevent from sunlight exposure.
  • Use electric fans, coolers, air-conditioners, and sleep in a cooler room in the house.
  • Turn off heat generating electrical and other equipment at home.

Heat stroke: read more


Heat stroke can lead to many complications depending on the duration for which there was exposure to hot temperature.

Damage to vital organs: Unless measures are taken to reduce the body temperature quickly, heat stroke can cause injury to the brain and other vital organs.
Death: If prompt treatment is not given, heat stroke can lead to fatality.

Next Steps

If you are working or engaged in physical activity in a hot environment and experiencing any symptoms suggestive of heat exhaustion such as fatigue, giddiness, rapid heart beat, etc., take measures to change to a cooler environment and cool the body.

Red Flags

If someone has symptoms of heat stroke that are not resolving within 30 minutes of cooling measures or if they have severe symptoms such as loss of consciousness, confusion, or fits, then seek emergency medical care.

Consult a top General Physician

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  • Bouchama A, Knochel JP. Heat stroke. N Engl J Med. 2002 Jun 20;346(25):1978-88.
  • NHS choices. Heat exhaustion and heatstroke. Accessed at http://www.nhs.uk/Conditions/Heat-exhaustion-and-heatstroke/Pages/Introduction.aspx
  • Chapter 65. Disorders of temperature control. Part II – Hyperthermia. In Irwin and Rippe’s Intensive Care Medicine. edited by Richard S. Irwin, James M. Rippe. Lippincott Williams & Wilkins, 2008.

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