Heat stroke or sun stroke is a heat-related medical emergency characterized by abnormal rise in the core body temperature, above 105ºF. This is different from “stroke” which refers to lack of oxygen supply (ischemia) to the brain. In the United States, heat stroke accounts for approximately 240 deaths per annum.
Vigorous physical activity during summer places athletes and outdoor-laborers at high risk of exertional heat strokes. Classical or non-exertional heat stroke is observed in infants and old people due to inefficient thermoregulatory mechanisms. As per CDC surveys, most cases of heat-related illnesses are reported during the hot and humid month of August. It is predicted that with global warming and increased occurrences of heat waves, the incidence of heat stroke will rise probably leading to more deaths from this condition.
The major symptom of heat stroke is hyperthermia or elevated body temperature and a resultant red, hot and dry skin. This may accompanied by symptoms of heat exhaustion such as headaches, malaise, shallow breathing and nausea.
With increasing delay in treatment, inflammatory responses are triggered in the body and signs of rhabdomyolysis (severe damage to muscles), hepatic failure and central nervous system defects such as confusion, disorientation, seizures and unconsciousness are observed.
The symptoms of heat stroke make its diagnosis rather apparent. However, the doctor may prescribe additional tests such as estimation of sodium-potassium levels in blood, verification of urine color and evaluation of muscle function.
Hyperthermia occurs when the rate of heat generation in the body exceeds the rate at which it is dissipated. When the body gets heated, sweat is secreted and as the sweat evaporates, the body cools. With loss of fluid and the onset of dehydration, sweating is reduced to conserve body fluids and this slows down heat dissipation from the body. The following conditions cause loss of body fluids, thus increasing the risk of heat stroke:
- Hot environment
- Physical exertion
- Insufficient rehydration
- Drinking sweetened, caffeinated or alcoholic beverages
- Intake of diuretics, heart disease medications (anti-convulsants, anti-hypertensives, anti-arrythmics, vasodilators), anti-depressants, anti-convulsants
- Polyuria in diabetics
- Drug abuse (cocaine and metamphetamine)
Heat stroke can be easily prevented by avoiding or minimizing outdoor activities during periods of harsh sunlight or heat waves and staying in well-ventilated, cool places. If unavoidable, adequate measures need to be taken to prevent dehydration. Light colored and slightly loose clothes made from fabric that allows for air flow should be worn.
Immediate attention must be given to a heat stroke victim to prevent complications like multi-organ failure that may also become fatal.
The treatment of heat stroke focuses on cooling the patient’s body to restore the normal body temperature of 37ºC. The patient should be shifted to a cool, shaded or air-conditioned area. They must be rehydrated with plenty of cold water, oral rehydrating solutions or sports beverages to restore electrolyte balance. Fruit juices and caffeinated drinks such as tea promote dehydration and therefore must be avoided.
Ice packs placed on the forehead, armpits and groin help to reduce body heat. Fanning the patient helps faster evaporation of the sweat and cooling of the body.