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 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:
