Heat
stroke is the leading cause of weather-related deaths in the United States, claiming
more lives in 2018 than tornadoes and floods combined, according to
data from the National Weather Service. And it doesn't discriminate:
A professional athlete perished on the field last year,
another died recently after working at his family's shop, and a
record number of kids have died in hot cars. High temperatures are going to remain a reality of our planet, and it's
crucial that we not dismiss the risks associated with them. Here's
what you need to know to keep your patients safe from heat exhaustion,
and to prevent heat exhaustion from turning to heat stroke.
Heat stroke, also known as sunstroke or hyperthermia, is defined as a body temperature
of 104˚ F or higher. There are two types of heat stroke: exertional, resulting
from prolonged physical activity in hot weather (think footballers in
the sun, triathletes in August); or passive, resulting from progressive
dehydration.
In both cases, the body gains heat faster than it is able to lose it. We
normally get rid of excess body heat by sweating, but severely dehydrated
bodies lose their ability to do so, thereby becoming unable to dissipate
heat. As a result, core temperature rapidly rises.
In either case, "approaches to hyperthermia are really about prevention
and management, and preparation beforehand," Bert Mandelbaum, MD,
an orthopedic surgeon and sports medicine physician, told Medscape.
Full-blown hyperthermia is usually preceded by heat exhaustion. The initial
symptoms are weakness and fatigue. Untreated, they can be followed by
confusion, disorientation, nausea, vomiting, and eventually death.
Exertional Hyperthermia Prevention and Treating Athletes
There are many
risk factors for exertional heat stroke: a hot environment, very strenuous exercise, inappropriate clothing that
may prevent evaporation of sweat, lack of adequate adaptation to the heat,
excess body fat among some athletes, and poor fitness level.[1-3] What's more, athletes who are overly motivated are at risk for overheating
by pushing themselves too hard and too fast. Ultimately, the lack of acclimation
to summertime temperatures is a key predictor of heat stroke.
The annual New York Triathlon, which was supposed to take place on Sunday, July 21,
was canceled for the first time because of an excessive heat warning. "I think it's a great move
in prevention," said Mandelbaum. Because the triathlon has no admission
criteria, it was near certain that some of the competitors simply wouldn't
be prepared to compete in extreme heat and humidity. "We can take
a very spartan approach to everything and say only the strongest survive,
but at this point in time we have a higher level of discernment."
Athletes planning to compete in extreme temperatures need to plan ahead.
"It takes a few weeks [of training] before you're ready to compete
in any hot weather event," Robert Glatter, MD, an emergency medicine
physician, told Medscape. "That time allows your body to hold on
to more water and more salt, and allows you to sweat more efficiently.
Athletes at high levels sweat earlier, more effectively, and more diffusely
throughout their surface area."
Training results in more efficient intake of fluids including salt and
other electrolytes.[4] The body becomes more effective at holding on to water and salt, leading
to greater blood volume pumped at a lower heart rate.
While fluids are crucial to preventing heat stroke, adequate hydration
is only a small part of prevention. Cardiovascular fitness is also key,
as dehydration elevates heart rate and reduces cardiac output. What's
more, it's not just the temperature that matters; the heat index is
a far more important predictor of the potential for heat-related illness.
For athletes, the use of stimulants and supplements is an additional risk
factor, as these impair sweating. Ultimately, the prevention of heat stroke
revolves around acclimation, proper hydration, pacing oneself, and having
rapid and effective cooling protocols in place. Taking frequent rest breaks,
moving into the shade, and drinking ahead of thirst can be lifesaving.
If symptoms appear, athletes should be able to recognize them and
have a plan in place for rapid cooling.[5] "The first thing they should do when they have signs of heat exhaustion
is get to a cooler environment, get to shade, get some ice, and see what
the response is," said Mandelbaum. If there is no response and a
temperature in excess of 104˚ F, the patient should be transported to
the nearest hospital.
Passive Hyperthermia Prevention
It isn't just athletes who are at
risk for heat-related illness.[6] "It goes well beyond athletes. It's everyday people," said
Glatter. "People who work in hot environments, underground, or in
the hot sun who are not dressing properly, not drinking enough fluids,
not eating properly."
For the general population, prevention is also key: wearing loose-fitting,
light-colored clothing; drinking ahead of one's thirst; and carrying
water. Nutrition is as important as hydration. "People think that
somehow eating less is better. On the contrary, you need to have the right
type of food — fruits and vegetables that are hydrating, like cucumbers
and watermelon," said Glatter. "When you sweat, you lose sodium, you lose
fluoride, but your body also needs sugar. The sugar and salt are key." Too
much sugar, however, can lead to dehydration.
For people who aren't athletes but plan on exercising strenuously in
the sun for an hour or more, Glatter recommends a sports drink to replace
lost electrolytes, or snacks such as salty pretzels or fruit. "If
you're starting to feel winded, you're feeling fatigued or lightheaded,
you're already past the threshold where you're at risk for heat-related
illness," said Glatter.
Children, pregnant women, people with diabetes, and the elderly are at
highest risk. Glatter recommends checking all patients' medications,
as antihistamines, diuretics, and antidepressants impair the ability to
sweat. High blood pressure, heart disease, or excess body fat can also
be a risk factor for heat stroke.
Surprisingly, heat exhaustion can also be developed indoors. "I've
had a few older people who don't like their air conditioners come
in [to the emergency department] with signs of heat stroke from hot environments
overnight," said Glatter.
Just like with exertional hyperthermia, it's critical to cool down
at first onset of symptoms, and seek medical attention if symptoms don't
subside or get worse.
"The take-home is that an ounce of prevention is worth more than anything,"
said Glatter. "Every doctor, every medical provider, should be aware
that if you don't have a discussion with patients ahead of time, they
could end up in the emergency department because they didn't plan
effectively, and they didn't think about the things that could lead
to heat-related illness."
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Medscape Emergency Medicine © 2019 WebMD, LLC
Any views expressed above are the author's own and do not necessarily
reflect the views of WebMD or Medscape.
Cite this: Exercising in Extreme Heat -- How to Avoid Hyperthermia -
Medscape - Aug 13, 2019.
https://www.medscape.com/viewarticle/916751