/ Health Articles / Diseases & Treatments /
Be careful of heatstroke – a potentially life-threatening form of heat illness

Get to know heatstroke

Heatstroke or sunstroke is an emergency condition caused by the body overheating. It is usually a result of prolonged exposure to or physical exertion in high temperatures. Regarded as the most serious form of heat illness, heatstroke can develop if body temperature rises to 40’ C (104’ F) or higher. This condition frequently occurs in summer months or humid climate.

Heatstroke requires emergency treatments. If left untreated, heatstroke can instantly damage multiple organs, including brain, heart, kidneys and muscles. In case that the treatment is delayed, the damage worsens, increasing risk of serious complications, long-term disability or even death.

Heatstroke VS. Stroke

Although both heatstroke and stroke are medical emergencies, heatstroke is not the same as a stroke. A stroke is diagnosed when a patient has sudden abnormal neurological symptom (s) that occurred from abnormalities of blood vessel. There are two major types of stroke. An ischemic stroke is caused by a blockage or reduced blood flow in an artery, preventing brain tissue from getting sufficient oxygen whereas a hemorrhagic stroke happens when a blood vessel bursts, causing bleeding in the brain. Warning signs and symptoms of stroke include a sudden paralysis or numbness of the face, arm or leg, trouble speaking and understanding, facial droop, trouble walking or balance problem. Similar to heatstroke, stroke needs immediate treatments. Nevertheless, diagnostic approaches and treatment plans are considerably different.   


Heatstroke can be classified into 2 types based primarily on its causes.

  1. Classic Heatstroke or Non-Exertional Heatstroke
    Being in a hot environment promotes a rise in core body temperature. Classic or non-exertional heatstroke typically occurs after exposure to hot and humid weather, especially for extended periods.
  2. Exertional Heatstroke
    Exertional heatstroke is induced by strenuous activity or intense physical activity in hot weather, resulting in an increase in core body temperature.

    Despite the fact that anyone exercising or working in hot weather can get exertional heatstroke, it is more likely to develop if a person is not used to hot climate. In addition, heatstroke can be brought on by wearing excess clothing that prevents sweat from evaporating easily and drinking alcohol which affects temperature regulation as well as becoming dehydrated by not drinking sufficient water to replenish fluids lost through sweating.

Risk factors

 Contributing factors to heatstroke often include:

  • Age: In the very young or in the elderly, the ability to cope with changes in body temperature is deteriorated. Moreover, both age groups usually have difficulty remaining hydrated.
  • Certain underlying diseases: Some chronic illnesses, such as heart disease and lung disease as well as obesity and physical inactivity potentially increase the risk of heatstroke.
  • Certain medications: Some medications affect body’s ability to maintain hydration and respond to heat properly. These medications include vasoconstrictors, beta blockers, diuretics and psychiatric drugs, such as antidepressants, antipsychotics and psychostimulants. Illicit stimulants, such as amphetamines and cocaine also make people more vulnerable to heatstroke.
  • Sudden exposure to hot weather: People become more susceptible to heatstroke if they are exposed to a sudden increase in temperature, such as during an early summer heat wave or when they travel to a hotter climate.


Signs and symptoms

Heatstroke signs and symptoms include:

  • A core body temperature of 40 ’C or higher
  • Altered mental status or behavioral changes, such as confusion, agitation, irritability, delirium, seizures and coma
  • Rapid breathing and racing heart rate
  • Headache
  • Nausea and vomiting
  • Red, hot and dry skin. However, in exertional heatstroke brought on by strenuous exercise, skin may feel slightly moist.


To diagnose heatstroke, medical history related to heat exposure needs to be obtained including risk factors that induce heatstroke.  Besides physical examination and core body temperature measurement, laboratory tests and imaging may be used to help confirm the diagnosis, rule out other possible causes and assess the associated organ damages.

If a person may be experiencing heatstroke, it is highly recommended to seek immediate medical assistance from the nearest emergency services.

In patients with preexisting neurological conditions, such as multiple sclerosis, stroke or epilepsy, their symptoms can be aggravated after exposure to high temperature for prolonged periods. However, the mechanisms are different among different diseases.


First aid involves taking immediate action to reduce the body temperature of the overheated person while waiting for emergency treatment.

  • Get the person into shade or indoors with air-conditioning.
  • Remove excess or tight clothing.
  • Cool the person with whatever means available, such as placing ice packs or cold, wet towels on the person’s head, neck, armpits and groin, putting the patient in a cool tub of water or a cool shower and spraying with water while waiting for an ambulance.

Another important point to remember while providing first-aid assistance is that the overheated person must be strictly refrained from sugary or alcoholic beverages since these drinks alter the body’s ability to regulate the core temperature. Moreover, cold beverages must be avoided as they can cause blood vessel and stomach constriction, leading to abdominal cramp.


If heatstroke is not treated in a timely manner, it can result in a number of complications, depending on how long the body temperature has been high. Without prompt and adequate treatment, heatstroke can be fatal.   Severe complications include:

  • Brain: convulsion, brain swelling (cerebral edema) and permanent damage of neuronal cells.
  • Muscle: the breakdown of skeletal muscle (rhabdomyolysis).
  • Kidney: acute kidney injury caused by the breakdown of skeletal muscle that releases the content into bloodstream.  
  • Liver: acute liver dysfunction caused by dehydration and less blood supply to the liver.
  • Heart: arrhythmias and heart failure induced by overworked heart.
  • Lung: serious lung condition that causes low blood oxygen (acute respiratory distress syndrome).
  • Coagulation system: either bleeding tendency or blood clots in the body.


To prevent heatstroke, it is recommended to take these following steps:

  • Wear loose or light weight clothing when exposing to the heat or poorly ventilated areas.
  • Protect against sunburn by wearing wide-brimmed hats, sunglasses and a broad-spectrum sunscreen with an SPF of at least 15.
  • Drink plenty of water and stay hydrated to maintain a normal body temperature.
  • Talk to your physician and take extra precautions with certain medications that affect body’s ability to control temperature and dissipate heat.
  • Avoid strenuous activity or vigorous exercise in hot, humid or poorly ventilated areas. If unavoidable, spend time as less as possible.



Dr. Doungporn Ruthirago
Neurointensivist, Neuroscience Center, Bangkok International Hospital

Dr. Pavis Laengvejkal
Neurointensivist, Neuroscience Center, Bangkok International Hospital.

For more information, please contact
Neuroscience Center, Bangkok International Hospital.
Tel: +662-310-3000 or 1719 (local calls only)
Email: [email protected]