This came from Graydon Thorne,  Safety Coordinator for Lone Star PCA.
Being aware of a student's physical condition during an event can help
us instruct and possibly save a life. We can also use this on ourselves
while at events. It is good data and sent with his permission.
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DEHYDRATION PRIMER

Usually with water loss due to heat, we think of 3 problems

Heat Cramps
Heat cramps are muscle contractions, usually but not always in the
gastrocnemius or hamstring muscles (the muscles at the back of the
calves). These contractions are forceful and painful.

These cramps seem to be connected to heat, dehydration, and poor
conditioning, rather than to lack of salt or other mineral
imbalances. They usually improve with rest, drinking water, and a
cool environment.  Also it helps to work out at the gym when not at
the track.

Heat Exhaustion
Although partly due to exhaustion -- and feeling like exhaustion, as
the name implies -- heat exhaustion is also a result of excessive
heat and dehydration. The signs of heat exhaustion may include dry
mouth, paleness, dizziness, nausea, vomiting, fainting, poor
judgment and the feeling that the laws of physics do not apply to
you or your car(Note that some of these symptoms are similar to those
secondary to carbon monoxide exposure). Rest and water may help in
mild heat exhaustion, and ice packs and a cool environment sometimes
with a fan blowing may be necessary in more extreme cases.  Even more
severely exhausted patients may need IV fluids, especially if
vomiting keeps them from drinking enough.  Hopefully we don't go this
far at the track.

Heat Stroke
 Heat stroke is a medical emergency!

Heat stroke is the most severe form of heat illness. It can occur
even in people who are not exercising, if the weather is hot enough.
These people have warm, flushed skin, and do not sweat. Athletes who
have heat stroke after vigorous exercise in hot weather, though, may
still be sweating considerably. Whether exercise-related or not,
though, a person with heat stroke usually has a very high
temperature (106 degrees F or higher), and may be delirious,
unconscious, or having seizures. These patients need to have their
temperature reduced quickly, often with ice packs, and must also be
given IV fluids for rehydration; they must be taken to the hospital
as quickly as possible (EMS is appropriate here), and may have to
stay in the hospital for observation since many different body organs
can fail in heat stroke. We better not be seeing this at the track.

Gobbledy gook theory (do not need to read)

Your sweat is your body's main system for getting rid of extra heat.
When you sweat, and the water evaporates from your skin, the heat
that evaporates the sweat comes mainly from your skin. As long as
blood is flowing properly to your skin, extra heat from the core of
your body is "pumped" to the skin and removed by sweat evaporation.
If you do not sweat enough, you cannot get rid of extra heat well,
and you also can't get rid of heat as well if blood is not flowing to
the skin. Dehydration will make it harder for you to cool of in two
ways: if you are dehydrated you won't sweat as much, and your body
will try to keep blood away from the skin to keep your blood pressure
at the right level in the core of your body. But, since you lose
water when you sweat, you must make up that water to keep from
becoming dehydrated.

 If the air is humid, it's harder for your sweat to evaporate -- this
means that your body cannot get rid of extra heat as well when it's
muggy as it can when it's relatively dry.  Why....because the air is
already wet so the wetness on your skin does not evaporate into the
air as well so there is a less efficient heat transfer from you to
the air.

Treatment (start to read again)

It's smarter to stay ahead of the game.  Your thirst mechanism will
kick in but you will be behind the eight ball and likely suffer some
of the symptoms of dehydration such as poor judgment.  As you know,
a dilute urine and peeing frequently are your clues to good
hydration.  Don't forget that caffeine is a diuretic which means that
you pee more out than you take in.  Therefore its ok to drink it as
long as you are very vigilant and also drink lots of water to stay
ahead of the game.  Don't forget...stay ahead of your thirst
mechanism.  The best fluid to drink when you are sweating is water.
Although there is a little salt in your sweat, you don't really lose
that much salt with your sweat, except in special circumstances;
taking salt tablets may raise your body's sodium level to hazardous
levels. "Sport drinks" such as Gatorade® are fine, too, but water
is easier to obtain.  The clothing you wear makes a difference, too: the
lighter that clothing is, the easier you can cool off.