Heat stroke is a form of hyperthermia, an abnormally elevated body temperature with accompanying physical and neurological symptoms. Unlike heat cramps and heat exhaustion, two other forms of hyperthermia that are less severe, heat stroke is a true medical emergency that can be fatal if not properly and promptly treated, according to medical experts.

The body normally generates heat as a result of metabolism, and is usually able to dissipate the heat by either radiation of heat through the skin or by evaporation of sweat. However, in extreme heat, high humidity, or vigorous physical exertion under the sun, the body may not be able to dissipate the heat and the body temperature rises.

“Heat stroke is a life-threatening illness characterized by an elevated core body temperature that rises above 40 C and central nervous system dysfunction that results in delirium, convulsions or coma,” says Sherif Mahmoud Affifi, Jeddah-based health expert at Bupa Arabia. Another cause of heat stroke is dehydration. A dehydrated person may not be able to sweat fast enough to dissipate heat, which causes the body temperature to rise.

Aside from elderly people of over 65 years of age (often with associated heart, lung and kidney diseases, or who are taking medications that make them vulnerable to dehydration and heat strokes), infants and children, those overweight or with chronic medical conditions maybe prone to heat strokes because of their tendency to retain more body heat. Also, people who overexert at work or exercise may become dehydrated and suffer a heat stroke, especially athletes and individuals who work outside and physically exert themselves under the sun.

Symptoms of heat stroke can sometimes mimic those of heart attack or other conditions. Sometimes a person experiences symptoms of heat exhaustion before progressing to heat strokes. Signs and symptoms of heat exhaustion include nausea, vomiting, fatigue, weakness, headache, muscle cramps and aches, and dizziness.

However, some individuals can develop symptoms of heat stroke suddenly and rapidly without warning.

Taking precautions against overheating and dehydration can reduce the risk of heatstroke. Light, loose-fitting clothing will allow perspiration to evaporate and cool the body. Wide-brimmed hats in light colors keep the sun from warming the head and neck; vents on a hat will allow perspiration to cool the head. Strenuous exercise should be avoided during daylight hours in hot weather.

In environments that are not only hot but also humid, it is important to recognize that humidity reduces the degree to which the body can lose heat by evaporation. In such environments, it helps to wear light clothing such as cotton that is pervious to sweat but impervious to radiant heat from the sun. This minimizes the gaining of radiant heat, while allowing as much evaporation to occur as the environment will allow. Clothing such as plastic fabrics that are impermeable to sweat and thus do not facilitate heat loss through evaporation, can actually contribute to heat stress.

In hot weather people need to drink plenty of liquids to replace fluids lost from sweating. Thirst is not a reliable sign that a person needs fluids. “Fluid intake during hot weather needs to be increased. Heavy sweating also removes essential salt and minerals from the body and must be replaced. If outdoors the head should be always covered and sunscreen of SPF 15 or higher applied 30 minutes prior to going out to protect the body from harmful ultra violate (UV) radiation that can cause cancer.

“The typical signs for heat stroke are an extremely high body temperature, no sweat, rapid and strong pulse, throbbing headache, dizziness, nausea and unconsciousness.” Affifi said. “If you see any of these signs, you may be dealing with a life-threatening emergency and should seek immediate medical assistance.”

It is important to try to cool down the affected person by either showering him with cold water or move him to a shaded area as quickly as possible. However, the most important thing for the victim is not to drink, he says.

Sometimes the victim’s muscles will begin to twitch uncontrollably as a result of heat stroke. If this happens, the affected person should be prevented from injuring himself, however, no objects should be placed in the mouth or fluids applied. If there is vomiting, the airways should remain open by turning the affected person on his or her side.

A better indicator is the color of urine. A dark yellow color may indicate dehydration. It is debated whether water or sports drinks are more effective to regain fluids. However, drinking only water without ingesting any salts will lead to a condition known as hyponatremia, or low sodium, which can cause sudden death from heart attack. By sweating and urination, humans lose salts, which need to be replaced along with fluids.

The Occupational Safety and Health Administration in the United States publishes a heat stress Quick Card that contains a checklist designed to help prevent heat stress. The list includes: Know signs/symptoms of heat-related illnesses, block out direct sun or other heat sources, use cooling fans/air-conditioning and rest regularly, drink lots of water about one cup every 15 minutes, and wear lightweight, light colored, loose-fitting clothes. Avoid caffeinated drinks or heavy meals.