Risk of serious illness or death from heat-related conditions is very low if treatment starts early
When British TV doctor Michael Mosley died
last year in Greece after walking in extreme heat, local police said “heat
exhaustion” was a contributing factor.
Since then, a coroner could not find a
definitive cause of death but said this was most likely due to an un-identified
medical reason or heat stroke.
Heat exhaustion and heat stroke are two
illnesses that relate to heat.
So what’s the difference?
A spectrum of conditions
Heat-related illnesses range from mild to
severe. They’re caused by exposure to excessive heat, whether from hot
conditions, physical exertion, or both. The most common ones include:
-heat oedema: swelling of the hands, feet
and ankles
-heat cramps: painful, involuntary muscle
spasms usually after exercise
-heat syncope: fainting due to overheating
-heat exhaustion: when the body loses
water due to excessive sweating, leading to a rise in core body temperature
(but still under 40°C). Symptoms include lethargy, weakness and dizziness, but
there’s no change to consciousness or mental clarity
-heat stroke: a medical emergency when the
core body temperature is over 40°C. This can lead to serious problems related
to the nervous system, such as confusion, seizures and unconsciousness
including coma, leading to death.
Some symptoms of heat stroke and heat
exhaustion overlap. This makes it hard to recognise the difference, even for
medical professionals.
How does this happen?
The human body is an incredibly efficient
and adaptable machine, equipped with several in-built mechanisms to keep our
core temperature at an optimal 37°C.
But in healthy people, regulation of body
temperature begins to break down when it’s hotter than about 31°C with 100%
humidity (think Darwin or Cairns) or about 38°C with 60% humidity (typical of
other parts of Australia in summer).
This is because humid air makes it harder
for sweat to evaporate and take heat with it. Without that cooling effect, the
body starts to overheat.
Once the core temperature rises above
37°C, heat exhaustion can set in, which can cause intense thirst, weakness,
nausea and dizziness.
If the body heat continues to build and
the core body temperature rises above 40°C, a much more severe heat stroke
could begin. At this point, it’s a life-threatening emergency requiring
immediate medical attention.
At this temperature, our proteins start to
denature (like an egg on a hotplate) and blood flow to the intestines stops.
This makes the gut very leaky, allowing harmful substances such as endotoxins
(toxic substances in some bacteria) and pathogens (disease causing microbes) to
leak into the bloodstream.
The liver can’t detoxify these fast
enough, leading to the whole body becoming inflamed, organs failing, and in the
worst-case scenario, death.
Who’s most at risk?
People doing strenuous exercise,
especially if they’re not in great shape, are among those at risk of heat
exhaustion or heat stroke. Others at risk include those exposed to high
temperatures and humidity, particularly when wearing heavy clothing or protective
gear.
Outdoor workers such as farmers,
firefighters and construction workers are at higher risk too. People with
certain health conditions, such as diabetes, heart disease, or lung conditions
(such as COPD or chronic obstructive pulmonary disease), and people taking
blood pressure medications, can also be more vulnerable.
Adults over 65, infants and young children
are especially sensitive to heat as they are less able to physically cope with
fluctuations in heat and humidity.
How are these conditions managed?
The risk of serious illness or death from
heat-related conditions is very low if treatment starts early.
For heat exhaustion, have the individual
lie down in a cool, shady area, loosen or remove excess clothing, and cool them
by fanning, moistening their skin, or immersing their hands and feet in cold
water.
As people with heat exhaustion are almost
always dehydrated and have low electrolytes (certain minerals in the blood),
they will usually need to drink fluids.
However, emergency hospital care is
essential for heat stroke. In the hospital, health professionals will focus on
stabilising the patient’s:
-airway (ensure no obstructions, for
instance, vomit)
-breathing (look for signs of respiratory
distress or oxygen deprivation)
-circulation (check pulse, blood pressure
and signs of shock).
Meanwhile, they will use rapid-cooling
techniques including immersing the whole body in cold water, or applying wet
ice packs covering the whole body.
Take home points
Heat-related illnesses, such as heat
stroke and heat exhaustion, are serious health conditions that can lead to
severe illness, or even death.
With climate change, heat-related illness
will become more common and more severe. So recognising the early signs and
responding promptly are crucial to prevent serious complications.
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