I ran across this information the other day, and since Burning Man is coming up , I thought I'd come out of lurk mode to post this information related to a condition known as hyponatremia. This is a condition where you are probably adequately hydrated, but your body is deficient in one of the most important eletrolytes: sodium. I thought I'd mention it just in case it helps someone, because it's not nearly as well-known as dehydration.
This is especially for those of you whose bodies are not acclimated to an arid climate (yes, your body does acclimate to humidity levels as well as elevation) and those of you who might be partaking in mind-altering substances. Most any drug will mess with your sense of time, your awareness of your body, or both, and it's easy to forget to eat and drink for a while. If it's especially hot, you may find yourself losing quite a bit of water by perspiration. If your body is not acclimated to the desert, your perspiration output may be quite high -- the human body can pump out several liters of sweat per hour. This of course can cause dehydration, but if you're only drinking water and not eating much, you're losing sodium too, and that can cause problems of its own. As stated below, drinking water may exacerbate the condition. Drinking Gatorade, which provides you with sodium, potassium and glucose as well as water, may help prevent the condition, but I wouldn't recommend relying on it.
The information below is from the Wilderness Medicine Institute. What I've stated above is based on my own knowledge as a Wilderness First Responder. Although what's below does contain information about treatment of the condition, please don't take it upon yourself to treat it unless you know what you're doing. This is more to give you the means to recognize it and seek medical help, rather than just giving the patient extra water.
At the Grand Canyon Clinic where Tom Myers, MD, practices his medical
skills, hyponatremia as a diagnosis was virtually unheard of ten years
ago. It currently accounts for more than 30 percent of the heat related
complications he sees. Why? Because people are drinking lots of
water--they got that message--but they aren't consuming adequate
electrolytes. The formula for disaster is relatively simple: Salt loss
in sweat exceeding salt intake plus water intake exceeding water loss
equals lowered sodium level in the blood. When blood sodium gets too
low, you have a case of hyponatremia.
Signs and symptoms may vary between individuals and the how low the
sodium level has sunk. Common complaints include headache, weakness,
fatigue, lightheadedness, muscle cramps, nausea with or without
vomiting, sweaty skin, normal core temperature, normal or slightly
elevated pulse and respirations, and a bit of anxiety. Sound familiar?
Yep, it sounds like heat exhaustion. But if you treat it like heat
exhaustion--just add water--you are harming the hyponatremia patient.
More severe symptoms of hyponatremia include a patient who is
disoriented, irritable, and combative--which gives the problem a more
common name: water intoxication. Untreated, the ultimate result will be
seizures, coma, and death.
"Of critical importance to the diagnosis," writes Dr. Myers, "is an
accurate history." Relatively little salty food intake combined with
relatively high fluid intake-say several liters in the last few
hours--should make you highly suspicious. If the patient's urine output
is clear and copious (urination occurring every few hours to several
times per hour) combined with a lack of thirst, you'll draw closer to
diagnosing hyponatremia. Heat exhausted patients typically have a low
output of yellowish urine (urinating every 6-8 hours) combined with
Patients with mild to moderate symptoms and a normal mental status may
be treated in the field: Rest in shade with no fluid intake and a
gradual intake of salty foods while the kidneys reestablish a sodium
balance. Once a patient develops hunger and thirst combined with normal
urine output, the problem is solved. Restriction of fluids for someone
who is well hydrated, fortunately, is harmless. Dr. Myers warns,
however, that giving oral electrolyte replacement drinks, such as
Gatorade, alone might damage the patient. These drinks are so low in
sodium and so high in water the dilutional imbalance may be increased.
Only a blood test confirms hyponatremia beyond doubt. If you just can't
make up your mind--is it heat exhaustion or hyponatremia?--give the
patient electrolyte replacement drinks and salty food, and monitor
closely for improvement. Concerning patients with an altered mental
status there is no question: They demand rapid evacuation to a medical
Prevention is a matter of being sensible, which is so often the case.
Drink lots, yes, but eat salty foods regularly while exercising in heat.
"Relying on electrolyte replacement drinks alone," writes Dr. Myers, "is
absolutely ill advised." Nothing's wrong with the electrolyte drinks,
but don't forget to eat as well.