Kathleen Harder-Brouwer, MD
Ravalli Family Medicine
411 West Main Street
Hamilton, MT 59840
The "dog days of summer" are certainly upon us again and incidence
of both heat exhaustion and heat stroke are rising. It is important to
know the difference between these two heat related illnesses and how to
prevent and treat them in the field before one gets to a medical facility.
Heat exhaustion and heat stroke are not distinct illnesses, but instead
they are diseases on a continuum. In most cases, exhaustion progresses
to stroke if not recognized and treated. However, stroke can be the presenting
problem and, due to its degree of severity, it must be recognized and
treated aggressively. So, it is important to understand the differences
between the two conditions. Before those differences are outlined, it
is important to review how the body handles excessive heat. We are built
with mechanisms to help us respond to excessive heat. The process of radiation,
or transferring heat from the body to a cooler environment, accounts for
the greatest degree of heat balance (about 65%), but only works when the
body is warmer than the surrounding environment. Sweating contributes
another 30%, through the evaporation of the sweat on our skin. If the
sweat drips off the body, it does not cool us and only serves to increase
the chances of dehydration. These mechanisms are affected by many factors,
including age, disease, and medications. Both the old and the young do
not have the ability to maximize the processes in the body that assist
with radiant heat loss. Certain diseases, such as cardiac and thyroid
diseases, also interfere with this method of temperature balance. Both
prescription medications and illegal street drugs can also interfere in
radiant heat loss and sweating. All of this shows us that it is quite
easy to find oneself in a situation of heat illness.
Heat exhaustion presents with flu-like symptoms, including headache, vomiting,
muscle cramps and lack of appetite. The individual with heat exhaustion
is still sweating and their temperature may be normal, but is almost always
less than 106 degrees Fahrenheit. Heat stroke will have the same flu-like
presentation and sweating may or may not be present. The key important
difference is the presence of central nervous system (CNS or brain) dysfunction.
Those with heat stroke may be confused, delirious, unable to walk, have
seizures or be comatose. It is this CNS abnormality that must be recognized
as soon as possible, so that appropriate treatment can be instituted.
Those with heat exhaustion should be allowed to rest in a cool spot, given
fluids, given foods with glucose and general supportive care. Those with
stroke need aggressive pre-hospital treatment. Their clothes should be
removed and their skin sprayed with liquid and fanned to promote heat
loss. If available, ice bags should be placed on areas where large blood
vessels come near the skin surface (neck, axilla, groin, scalp). They
should not be given anything orally, due to the CNS dysfunction. Lastly,
if you are the person in charge of the backcountry group where an individual
has heat stroke, you should call for medical evacuation due to the seriousness
of this condition.
Like many other illnesses, the phrase "an ounce of prevention is
worth a pound of cure" applies in this situation. Most of us know
how to prevent heat illness: Drink lots of fluid, wear heat dissipating
clothing, avoid the sun when possible, avoid hard work or exercise in
the heat of the day. But, when those avoidance techniques fail, knowing
the difference between heat exhaustion and stroke can save a life. And
back to those "dog days of summer": it turns out that phrase
has nothing to do with sultry hot days. This was a phrase the Greeks and
Romans used regarding the position of the dog star, Sirius, in the summer
sky. The "dog days" occurred around the day when Sirius appeared
to rise just before the sun, in late July. They referred to these days
as the hottest time of the year, a period that could bring fever, or even
catastrophe. Heat illness can occur at any time of the year, but certainly
the phrase lives on in our culture.
This week's health column is collaboration between Ravalli Family
Medicine and Marcus Daly Memorial Hospital. For questions regarding the
health topic please contact Kathleen Harder-Brouwer, MD at Ravalli Family
Medicine, 411 West Main Street, Hamilton MT 59840 or
www.ravallifamilymedicine.com. Working together to build a healthier community.