What is heat stroke or sunstroke?

Date: Sep-24-2013Heat 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 are the signs and symptoms of heat stroke?

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:

A high temperature - The National Library of Medicine, USA, and the National Health Service, UK, say any temperature higher than 104°F (40°C). According to an article in Emergency Medicine Australia, any temperature over 40.6°C (105.1°F).

Heat stroke may be diagnosed at lower temperatures. Also, some people may reach these temperatures and never develop heatstroke.

Profuse sweating that abruptly stops - when the body cannot sweat any more, as may happen in cases of severe dehydration, the skin will become dry. Without perspiration the body has no way of cooling itself.

Accelerated (weak) heartbeat.

Hyperventilation. - rapid breathing, shallow panting.

Muscle cramps.

The skin becomes hot, dry and red.

Nausea.

Vomiting.

Dark urine
As the nervous system becomes affected, the following symptoms may emerge:

Confusion
Coordination problems
Seizures (fits)
Headache
Vertigo, dizziness, lightheadedness - a sensation of spinning or moving when standing (vertigo)
Anxiety
Restlessness
Hallucinations
Irrational behavior
Loss of consciousness

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.
What are the causes of heat stroke

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:

Radiation - heat radiates out of our body in the same way it radiates our of a fire.

Convection - when cool air or water crosses the skin the body is cooled.

Conduction - an object that is at a lower temperatures than our body temperature comes into direct contact with our skin - it conducts (draws out) heat from our body.

Evaporation - our bodies produce sweat, as the sweat evaporates it takes body heat with it.

Sweating

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:

Dehydration - excessive loss of water from the body.

Wrong clothing - for sweat to evaporate and take heat with it, the skin must have contact with air. Tight clothing undermines sweat's ability to evaporate, so the body cannot cool down properly.

High humidity - the higher the atmospheric humidity, the slower water evaporates. In other words, when it is humid sweating is less effective in cooling down the body. The problem is compounded if it is very humid and there is no breeze.

The two types of heatstroke, which tend to affect different population groups, are:

Military personnel sent to areas with high
temperatures are at risk of heat stroke

Classic heat stroke - more likely to occur during a heat wave or very hot weather. Babies, seniors and patients with chronic health conditions are more susceptible to classic heat stroke than the rest of the population.

The hypothalamus in elderly individuals and those with chronic conditions and illnesses does not work as well as it should in regulating body temperature.

Babies sweat less than older people, they are also more vulnerable to the effects of dehydration.

Exertional heat stroke - occurs as a result of physical exertion, strenuous and sustained exercise in a hot environment. Exertional heat stroke tends to affect younger people more, especially athletes, firefighters and military personnel.

Medications that raise the risk of heat stroke

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:

Beta blockers - medications for treating hypertension (high blood pressure), glaucoma and migraines.

Diuretics - any medication that increases the rate of urination, thus making the body shed fluids (water). People on diuretics have a higher risk of becoming dehydrated.

Neuroleptics - psychiatric drugs used to treat the symptoms of certain mental illnesses, including delusional disorder, schizophrenia, bipolar disorder, and psychotic depression. Neuroleptics depress nerve function.

Phenothiazines - medications that reduce the effect of dopamine in the brain. Used to treat schizophrenia or psychosis.

Anticholinergics - drugs that block the neurotransmitter acetylcholine in the central and the peripheral nervous systems. They are used for treating gastrointestinal disorders, genitourinary disorders, respiratory disorders (including asthma), insomnia and dizziness.

Cocaine and amphetamines - in very hot environments, people who take cocaine, crystal meth or speed have a much higher risk of developing heat stroke.

According to Drugs.com, tricyclic antidepressants, some Parkinson's disease drugs, laxatives and antihistamines can cause hyperthermia (excessively high body temperature).

Other causes of heat stroke may include:

Being obese or overweight - obese people are much more likely to suffer from heat stroke in very hot weather compared to people of normal body weight.

Sleep deprivation - if you do not get enough sleep, your rate of sweating can be reduced, making it harder for the body to control its core temperature.

Lack of acclimatization - people who are not used to hot weather, such as tourists or athletes competing away from home who move from a cool climate to a warm one, are more susceptible to heat stroke.

Previous heat stroke - an individual who had heat stroke before is at high risk of recurrence.

What are the treatment options for heat stroke?

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:

Move the patient to a cool place, preferably air-conditioned. If one is not available, go to a shady area.

Make sure the place is ventilated. Use a fan or open the windows (don't open windows if it is air-conditioned).

Try to get them to drink water.

Do not give any painkilling medications, such as ibuprofen, aspirin or acetaminophen (paracetamol, Tylenol).

If you can, place them in a cool (not cold) shower.

If there is one, partly fill a bathtub with cool (not cold) water, sit the person in there and hydrate their skin. Do not fully immerse the person in the water until the paramedics arrive.

A woman placed in the recovery position
To encourage blood circulation, gently massage their skin.

If the person has a seizure, do not place anything in their mouth. Move nearby objects out of the way.

If they are unconscious, place them in the recovery position. If they have vomited, make sure there is no blockage that may affect breathing.

Hospitalization

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

Ice bath - the bath is filled with ice and water and the patient is immersed in it.

Cooling blankets and ice - the patient in wrapped in cooling blankets and ice packs are placed under the arms, around the head and neck, and in the groin.

Evaporation cooling - the patient's body is sprayed with a mist of cool water. A fan creates a warm breeze which speeds up evaporation, and thereby heat loss. According to the journal American Family Physician, "Cooling rates with this technique have been measured at 0.31°C (0.56°F) per minute."

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:

Gastric, bladder and rectal cold-water lavage - these can be done with minimal invasion.

Peritoneal and thoracic lavage - these are only considered in very extreme cases.

Cardiopulmonary bypass - an extremely rare but effective cooling method.

What are the complications of heat stroke?

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.

The University of Maryland Medical Center writes "If left untreated, heat stroke can quickly lead to heart attack and death."
Video - How to treat a heat stroke

Jerome Chip Munna, a paramedic instructor, explains how to treat a heat stroke.

Written by Christian Nordqvist

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