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Researchers
at the National Institute for Occupational Safety and Health (NIOSH) learned
some important lessons about heat illness from the Deepwater Horizon
disaster. As a result, the agency has updated its Criteria for a Recommended Standard:
Occupational Exposure to Heat and Hot Environments for the
first time since 1986.
Here’s
what’s new in our understanding of heat illness.
Two Types of Heatstroke
The most
significant change to the NIOSH document is a change in the definition of
“heatstroke.” At one time, the accepted definition of “heatstroke” included
confusion, unconsciousness, and/or convulsions, accompanied by a lack of
sweating. In fact, workers were warned that if they stopped sweating,
heatstroke was imminent.
Unfortunately,
this type of heatstroke, now called “classic heatstroke,” isn’t the type that
most commonly strikes workers.
NIOSH has
recognized that another type of heatstroke, known as “exertional heatstroke,”
is more common in workers—and profuse sweating is one of its symptoms. So
workers who have been taught that sweating is a positive sign are actually at
increased risk.
Exertional
heatstroke is caused by the combination of heat exposure and heavy physical
exertion. It can lead to a condition called rhabdomyolysis, in which muscle
tissue breaks down, releasing large amounts of potassium into the blood. High
levels of potassium in the blood can lead to cardiac arrhythmias and
seizures. High levels of proteins released by muscle breakdown can cause
temporary or permanent kidney damage.
Symptoms of rhabdomyolysis include:
- Muscle pain and cramping
- Swelling
- Weakness
- Decreased
range of motion
- Fatigue
- Abdominal
pain
- Back
pain
- Nausea
or vomiting
- Confusion
However,
many cases occur with very mild symptoms that are mistaken for heat stress.
This creates a potentially dangerous situation because these workers don’t
receive the intensive medical intervention they require.
Another
potential complication of rhabdomyolysis is compartment syndrome, or swelling
in a specific type of muscle, usually in the lower extremities, that blocks
blood flow. Compartment syndrome is often delayed—it may take several hours
to develop—and can lead to permanent loss of function in the affected limb.
Symptoms of compartment syndrome include the
“5 P’s”:
- Pain
- Pallor
- Pulselessness
- Paresthesia
(sensation of tingling, numbness, or burning, usually felt in the hands,
feet, arms, or legs)
- Paralysis
Pain is
the most common and tends to be extremely severe. Workers who experience
these symptoms must go to a hospital immediately. Quick surgical intervention
is required to treat compartment syndrome.
Both
types of heatstroke are accompanied by extremely high body temperature, and
both types are a medical emergency that require immediate medical attention.
First aid includes cooling the worker as quickly as possible by any means
available, including an ice bath, circulating air around the worker, and
placing cold packs on the head, neck, armpits, and groin.
For
exertional heatstroke, oral hydration is vital—the more the victim drinks,
the more potassium and proteins will be flushed from the body. However, in
serious cases, it’s impossible for the victim to drink enough fluids to flush
out the proteins and potassium; the victim will need intravenous fluids.
Emergency medical services should be summoned immediately for all cases of
heatstroke, and victims should be transported to a hospital as soon as
possible.
A Warning from NIOSH
Because
exertional heatstroke is more likely to occur in workers than classic
heatstroke, NIOSH recommends that all workers exposed to hot working
conditions be retrained to recognize exertional heatstroke.
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