Heat stroke and other heat related conditions occur when the body is exposed to high levels of heat and is unable to cool itself. (1-4)
Normally the human body can maintain a stable body temperature despite varying temperatures externally in the environment. This is called thermoregulation.
Normal skin temperature is 32-34°C (89.6-93.2°F). A body normally uses some techniques to cool itself when the core temperature rises. These include:
When the environmental temperatures are higher than the body’s temperature, sweating is the first and most important way of cooling the body.
Sweating is regulated by a part of the brain called the hypothalamus. This part acts like a thermostat and stimulates sweating in response to excessive environmental heat. It also asks the body to stop sweating when the body is cool.
If the environmental air is not saturated with water, sweat will vaporize and cool the body surface.
The evaporation of 1.7 ml of sweat will consume 1 kcal of heat energy. At best sweating can dissipate about 600 kcal of heat per hour.
A severe lack of sweating may be caused by:
This may lead to increased core body temperature as the body fails to cool itself by its own.
Thus not only the environmental temperature but other factors like humid weather and physical exertion may also lead to heat strokes.
Heatstroke is of two types the classic and exertional heatstroke.
Classic heat stroke commonly affects infants and babies under two years of age, elderly and those with long-term health conditions like diabetes, heart and kidney disease. This is seen commonly during heat waves and hot weathers.
Exertional heatstroke on the other hand may affect younger people, especially if they are doing strenuous, physical activity in hot conditions for very long time.
This is commonly seen among athletes, military personnel, firemen and construction workers and manual labours working in the sun.
In the elderly and those with long term health conditions the thermoregulation of the brain is not adequate. This puts these individuals at a higher risk of getting heat exhaustion and heatstroke.
Further elderly women have a slightly higher risk of heatstroke than older men. This may be because they have fewer sweat glands than men. Infants and children under two years are also susceptible since they sweat less and are more affected by dehydration.
High risk groups include:
In addition, certain drugs also raise the risk of heat related health conditions. These include drugs of abuse like:
Medications that raise the risk of heat stroke include: