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Heat stroke, also known as sunstroke, is a serious medical condition, a medical emergency, when the body's temperature rises too high as a result of excessive heat exposure. The body loses its ability to cool itself and overheats.
When a person's body temperature is greater than 40.6°C (105.1°F), and this is caused by environmental heat exposure with poor thermoregulation (temperature control), they have heat stroke.
Heat stroke is not a fever, where the body deliberately raises its temperature in response to, for example an infection.
There are three levels of heat emergencies - heat cramps, heat exhaustion and heat stroke, with heat stroke being the most severe and life-threatening.
What is the difference between a sign and a symptom? A symptom is felt by the patient and described to those around him or her, for example, pain. A sign can be detected by others, for example, a skin rash.
Unlike the symptoms of heat exhaustion, which can develop rapidly, heat stroke signs and symptoms generally develop over several days, especially among elderly individuals and people with chronic health problems.
Heatstroke can develop rapidly in severe conditions and situations with extreme physical exertion (exertional heatstroke), especially if the person becomes dehydrated. Exertional heat stroke tends to affect young, physically active people more than sedentary or older individuals.
The signs and symptoms of heat stroke may include:
If you think somebody has heat stroke, call the emergency medical services. The numbers are: USA/Canada 911, UK/Ireland 999, European Union (including UK/Ireland) 112, Australia 000, New Zealand 111.
When the body is unable to cool itself and it begins to overheat, heat stroke is a likely complication.
The human body controls its core temperature (body temperature) by maintaining a tight balance between heat gain and heat loss.
While we are resting normal core temperature ranges between 36.5°C and 37.5°C (97.7°F and 99.5°F). The hypothalamus, a part of the brain, regulates our core temperature. The hypothalamus is sometimes called the body's thermostat.
There are several temperature receptors located in different parts of the body, to which the hypothalamus responds by making physiological adjustments to make sure the core temperature is constant. For example, temperature receptors in the skin tell the hypothalamus it is hot, which tells the sweat glands to produce more sweat.
When we do exercise, thermoregulation (temperature control) is a continuous challenge. Metabolism produces heat. The human body is not that efficient - 75% of our energy is lost in heat. During exercise, our core temperature can rise rapidly.
Our bodies have several ways of maintaining thermoregulation.
The human body can be cooled down in the following ways:
The normal temperature of the skin is 32°C -34°C (89.6°F -93.2°F). Any outside temperature above those ranges will result in the skin producing more sweat to cool the body down.
The following situations, can undermine the body's ability to thermoregulate through sweating:
The two types of heatstroke, which tend to affect different population groups, are:
Several medications can affect how the body regulates its core temperature, thus increasing the risk of heat stroke.
According to the National Library of Medicine, the following medications are known to raise the risk of heat stroke:
Other causes of heat stroke may include:
Heat stroke is a medical emergency. If you see somebody with heat stroke call for an ambulance straight away.
While you are waiting for the paramedics to come:
When the patient arrives in hospital, the medical team's priority is to get the core temperature down as rapidly as possible. There are two options - internal and external cooling methods.
External cooling methods
Disadvantages of ice baths or cooling blankets with ice packs include the occurrence of peripheral vasoconstriction and shivering. With these two methods it is also harder to access the patient if he or she experiences cardiac arrest or bradycardia (very slow heart beat).
Internal cooling methods
Internal cooling methods can bring the patient's core temperature down more rapidly. Examples include:
If medical help arrives rapidly, the risk of complications from heat stroke is low.
The journal American Family Physician says that about 20% of heat stroke cases lead to central nervous system injury with poor prognosis.
Heat stroke can lead to rhabdomyolysis, a condition in which damaged skeletal muscle tissue breaks down rapidly. When breakdown substances of damaged muscle cells enter the bloodstream, some of them, such as myoblogin, can harm the kidneys and cause kidney failure.
The medical journal Best Practice mentions acute respiratory distress syndrome (ARDS) as a possible complication of heat stroke. ARDS is a lung condition that leads to low blood oxygen levels. It can be life-threatening. The same journal also informs that multi-system organ failure is another possible heat stroke complication.
Jerome Chip Munna, a paramedic instructor, explains how to treat a heat stroke.
Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without the permission of Medical News Today.
National Library of Medicine --- National Health Service --- Emergency Medicine Australia --- Drugs.com --- American Family Physician --- Best Practice --- University of Maryland Medical Center --- Medical News Today archives.
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Nordqvist, Christian. "What is heat stroke or sunstroke?." Medical News Today. MediLexicon, Intl., 24 Sep. 2013. Web.
11 Dec. 2013. <http://www.medicalnewstoday.com/articles/266551>
Nordqvist, C. (2013, September 24). "What is heat stroke or sunstroke?." Medical News Today. Retrieved from
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