I recently had a test on fluid/electrolyte imbalances. One of the questions was how you would treat a man who came in with symptoms of dehydration after mowing his lawn on a hot summer day. The correct answer was to administer IV 0.45% NaCl solution, which is hypotonic.
As far as I know, diaphoresis is what caused his dehydration, and when you sweat you sweat both water and salt. However, my book lists "clinical dehydration" as ECF deficit along with hypernatremia. Why would you become hypertonic from dehydration if you are also sweating sodium? Is it not sufficient amounts of sodium to offset the water loss?
Additionally, if you are supposed to give hypotonic solutions for clinical dehydration, why is it that manual laborers and athletes need to hydrate with things like Gatorade, that contain electrolytes and are at risk of hyponatremia if they drink only plain water?
Any help or sources that you can offer is greatly appreciated!
Are you saying that is it easy to identify an electrolyte balance from symptoms alone? In my reading many seemed to present with similar symptoms, I wouldn't feel confident diagnosing (though I know it's not in out scope as nurses) based on that alone.
In general, would you say that it is flawed logic to assume that someone presenting as dehydrated is also hypertonic?
Yes, that is flawed logic. If IV fluids are indicated and if they are then what type is indicated is up to the MD, but as the patient's nurse you are expected to be able to judge if the medical plan is appropriate.
And that's the tricky part, "sweating in a desert" can result in either hypernatremia or hyponatremia based on additional information. Sweat contains about a third of the sodium per liter that blood does, so sweating without drinking any water will eventually result in hypernatremia, sweating and drinking water but not enough to match water losses will result in hyponatremia.
If books had been matching life exactly in at least 85% of cases, you and me would be jobless by now. But it doesn't look like happening any time soon :)
For the last 4 days we had awfully hot wave with correspondingly high number of new admits, all suffering from dehydration of every sort, shape and color. It is frightening to see how little physiologic reserve and common sense some folks walking and driving around of us have. Just an hour or two on hot sun, high humidity and 4 of 64 oz (oh, yeah, you read it right - "they told us to drink plenty!") regular Cokes while there, plus "my mornin' pee pee pill" - sodium 112, among other components of utter metabolic disaster.
Someone whose fluid loss is purely through sweating, without additional PO intake, will eventually become hypernatremic. In that instance, it is very reasonable to rehydrate with 1/2 NS. What you won't do with this fluid is give it as a bolus. That's not appropriate. Initial resus is done with NS (1-2 liters) and then once the labs are back, that's when they'd switch to the 1/2 NS. Think about where you want that water to go... back into the cells, right? You wouldn't want it all going back fast, and (basically) uncontrolled, right? Bad stuff happens when you do that. Dropping in a liter or two of 1/2 NS would result in reasonably fast movement of water back into cells. That causes problems, especially with neurons. I'm a Paramedic and I'm an ED RN, and I'm also educated as an athletic trainer.
While PO replacement with water is absolutely a good idea as is replacement with Gatorade (or similar drinks) know that the Gatorade you buy off the shelf in the supermarket is actually NOT formulated for fast absorption - it's too concentrated for that. The sports drinks that are actually supplied to athletes is basically a variation of a Ringer's Solution with some sugar and flavoring and tastes pretty weak compared to what you get in stores. Those drinks wouldn't sell well at all to the general public, so they made it more palatable. It is possible to buy powdered Gatorade (or other sports drinks) in packages meant for 5 or 10 gallon containers. Pour in the powder and fill with water. Then taste it... it won't be what you get in the store, but it'll be about perfect for rehydration. It will be absorbed in the gut as fast as water, about 1200 mL/hr.
Ideally, if you know the patient's body weight before the physical activity started and you determine the body weight upon presentation, you can pretty easily estimate fluid loss. Unfortunately that rarely happens in real life unless you're dealing with athletes. All my athletes were required to weigh themselves (and record it) before and after their workouts. That way we knew how much fluid loss they'd had. Almost all of them lost weight every day, even with lots of fluid breaks while at practice. Fluid loss via sweating can be well in excess of 2000 mL/hr....
Medschool Lange's Norm Physiology book says that normal concerntration of sodium in sweat 30 to 65 mmol/l, depending on the organism and acclimatization (the hotter the "usual" environment, the less it gets) and in serum it is 135 - 145. Counting that a human being can easily lose 2+ liters of water by sweating alone, it is not surprising that "sweating in desert" is indeed more likely to lead to hypotonic loss of volume, like the book says. But if we have "poorly acclimatized" patient whose body loses solutes easily and with relatively low reserve, then loss of salt can become significant as well.
If you are talking about a routine ER patient- Not actively vomiting, vitals stable, etc....
My first thought would be "This guy should have stayed home, drank some water or watered down Gatorade, and moved on with his life". Then,I would start a line and run a liter of NS in, probably before he was seen, certainly before labs were back.
Is this right? I don't know. It's how we roll where I work.
IF he looked crappy or complicated, I would get one of the docs to look at him. Then give him a liter of NS. The last time I used 0.45 in the ER was....
If you are looknig for the correct test answer, I don't know it.
Nursing school questions are ridiculous. There is very little practical use for these questions in the real world. You can't apply it, because it's not what happens.
I would not question a difference between 1/2 NS and NS on a physicians order. I would question this situation if say I saw an order for 3%. Sometimes I'll ask for a switch in fluids to LR or add some potassium in a fluid if need be by looking at lab values.
Seeing as how we don't prescribe it's a silly question and while yes, we need to make sure the treatment is appropriate, on this question, I'm not questioning if the physician orders NS, 1/2 NS, or Gatorade in this situation.
Shoot, if we sent every person who got a little dehydrated from mowing a lawn in the heat to the hospital our EDs would be jammed full of landscapers and yard guys on the daily. Heck, I get dehydrated every single week mowing my lawn in the summer. Maybe I should be worried. I really hate nursing school questions where the "right" answer isn't even close. Unless the guy was obtunded or there were some other reasonable contraindication I would have answered PO fluids. I can't recall ever using 0.45% routinely (some neuro kids yes) and certainly not for dehydration. When I was was in peds we used D5 .45NS as maintenance quite a bit.
Nursing school questions are ridiculous. There is very little practical use for these questions in the real world. You can't apply it, because it's not what happens.
What is really unfair is that schools teach nursing students all of this. Then students are sent into EDs and other settings to learn real world nursing in their independent studies. And then? Guess what, forget everything that happens in the real world, and go back to this imaginary land of textbook nursing to take your boards.
"It is important to realize the difference between HYPOVOLEMIA and DEHYDRATION, two terms which are often used interchangeably but in fact reflect different things. Read the Up-To-Date entry « Dehydration is not synonymous with hypovolemia » by Burton Rose if there is any confusion about this. HYPOVOLEMIA refers to any condition in which the extracellular fluid volume is reduced, and results in decreased tissue perfusion. It can be produced by either salt and water loss (e.g. with vomiting, diarrhea, diuretics, or 3rd spacing) OR by water loss alone, which is termed DEHYDRATION. Salt + water loss comes primarily from the extracellular fluid whereas pure water loss (dehydration) come from the total body water, only about 1/3 of which is extracellular. Thus for dehydration to produce the same degree of extracellular volume depletion as salt+water loss, 2.5 times as much fluid needs to be lost. Patients with DEHYDRATION are always hypernatremic."
I really hate nursing school questions where the "right" answer isn't even close. Unless the guy was obtunded or there were some other reasonable contraindication I would have answered PO fluids. I can't recall ever using 0.45% routinely (some neuro kids yes) and certainly not for dehydration. When I was was in peds we used D5 .45NS as maintenance quite a bit.
MunoRN, RN
8,058 Posts
Yes, that is flawed logic. If IV fluids are indicated and if they are then what type is indicated is up to the MD, but as the patient's nurse you are expected to be able to judge if the medical plan is appropriate.