Recognizing the Signs, Symptoms, and Treatment for different levels of Heat Stress
Heat stroke occurs when the body’s system of temperature regulation fails and body temperature rises to critical
levels. This condition is caused by a combination of highly variable factors, and its occurrence is difficult
to predict. Heat stroke is a medical emergency. The primary signs and symptoms of heat stroke are confusion;
irrational behavior; loss of consciousness; convulsions; a lack of sweating (usually); hot, dry skin; and an
abnormally high body temperature, e.g., a rectal temperature of 41°C (105.8°F). If body temperature is too
high, it causes death. The elevated metabolic temperatures caused by a combination of work load and environmental
heat load, both of which contribute to heat stroke, are also highly variable and difficult to predict.
If a worker shows signs of possible heat stroke, professional medical treatment should be obtained immediately.
The worker should be placed in a shady area and the outer clothing should be removed. The worker’s
skin should be wetted and air movement around the worker should be increased to improve evaporative cooling
until professional methods of cooling are initiated and the seriousness of the condition can be assessed.
Fluids should be replaced as soon as possible. The medical outcome of an episode of heat stroke depends on
the victim’s physical fitness and the timing and effectiveness of first aid treatment. Regardless of the worker’s
protests, no employee suspected of being ill from heat stroke should be sent home or left unattended unless a
physician has specifically approved such an order.
The signs and symptoms of heat exhaustion are headache, nausea, vertigo, weakness, thirst, and giddiness.
Fortunately, this condition responds readily to prompt treatment. Heat exhaustion should not be dismissed
lightly, however, for several reasons. One is that the fainting associated with heat exhaustion can be dangerous
because the victim may be operating machinery or controlling an operation that should not be left unattended;
moreover, the victim may be injured when he or she faints. Also, the signs and symptoms seen in heat
exhaustion are similar to those of heat stroke, a medical emergency.
Workers suffering from heat exhaustion should be removed from the hot environment and given fluid
replacement. They should also be encouraged to get adequate rest.
Performing hard physical labor in a hot environment usually causes heat cramps. These cramps have been
attributed to an electrolyte imbalance caused by sweating. It is important to understand that cramps can be
caused by both too much and too little salt. Cramps appear to be caused by the lack of water replenishment.
Because sweat is a hypotonic solution (±0.3% NaCl), excess salt can build up in the body if the water lost
through sweating is not replaced. Thirst cannot be relied on as a guide to the need for water; instead, water
must be taken every 15 to 20 minutes in hot environments.
Under extreme conditions, such as working for 6 to 8 hours in heavy protective gear, a loss of sodium may
occur. Recent studies have shown that drinking commercially available carbohydrate-electrolyte replacement
liquids is effective in minimizing physiological disturbances during recovery.
In heat collapse (fainting), the brain does not receive enough oxygen because blood pools in the extremities.
As a result, the exposed individual may lose consciousness. This reaction is similar to that of heat exhaustion
and does not affect the body’s heat balance. However, the onset of heat collapse is rapid and unpredictable. To
prevent heat collapse, the worker should gradually become acclimatized to the hot
environment.
Heat rashes are the most common problem in hot work environments. Prickly heat is manifested as red
papules and usually appears in areas where the clothing is restrictive. As sweating increases, these papules give
rise to a prickling sensation. Prickly heat occurs in skin that is persistently wetted by unevaporated sweat, and
heat rash papules may become infected if they are not treated. In most cases, heat rashes will disappear when
the affected individual returns to a cool environment.
A factor that predisposes an individual to heat fatigue
is lack of acclimatization. The use of a program of
acclimatization and training for work in hot environments
is advisable. The signs and symptoms of heat
fatigue include impaired performance of skilled sensorimotor,
mental, or vigilance jobs. There is no treatment
for heat fatigue except to remove the heat stress
before a more serious heat-related condition develops.