Confusion on the NA/water relationship

[swnewrngrad]

Ok, I am confused about the sodium water relationship. I thought that I had a pretty good grasp on the concept and made it all of the way through school and then I attended the HURST review and their section on this topic has confused me.... Does nausea and vomiting lead to hypernatremia or hyponatremia? I was under the understanding that NA follows water, but the hurst review states that nausea and vomiting lead to hypernatremia? I'm confused and would appreciate any help.

[shortnorthstudent]

Edit: Is my line of thinking correct here?

I'm just finishing my fluid/electrolytes in my pathophysiology course and I hope that someone could explain this to me better. I am sorry if my question shows my lack of knowledge. I am at the beginning of my road.

I thought that vomiting led to hypovolemia which is an isotonic dehydration. I thought that hypovolemia was isotonic and therefore neither hyper nor hyponatremic.

[RNTutor, BSN, RN]

I'm just finishing my fluid/electrolytes in my pathophysiology course and I hope that someone could explain this to me better. I am sorry if my question shows my lack of knowledge. I am at the beginning of my road.

I thought that vomiting led to hypovolemia which is an isotonic dehydration. I thought that hypovolemia was isotonic and therefore neither hyper nor hyponatremic.

That's actually a very insightful question. And you're right!

Dehydration is actually defined as loss of water with no loss in Sodium. Fluid volume deficit, however, would be a decrease in water AND sodium. Even though these 2 terms should not be used interchangeably, they often are, which can be rather confusing when you actually realize the difference :)

And you're right, vomiting usually loses water AND sodium. So it's actually pretty low-risk for hypernatremia, because it would be more likely to cause fluid volume deficit (not dehydration-review definitions above!). But since the initial poster was asking specifically if vomiting would be more likely to produce hyper or hypo, then I think everyone was responding with that assumption.

But to apply this to the thread's primary discussion, when you lose sodium AND water with vomiting, it's not because sodium is following water, or vice versus. It's simply because it's all just happens to be sitting in your stomach when you upchuck. It might help to visualize it this way. You have a bucket of salt water. You turn it upside down. All of the water and all of the sodium spill out onto the ground. Did one follow the other? No, not really, they both just followed the law of gravity! It's the same with vomiting. One is not really following the other in vomiting, it's just an external force (contraction of diaphragm etc) that causes the stomach to be squeezed, forcing everything that was inside...out.

[ggmugsy]

Oops! I just re-read through and I had gotten it backwards in one of my posts. Thanks so much all you knowledgeable nurses for getting us all on the right track.

[shortnorthstudent]

That's actually a very insightful question. And you're right!

Dehydration is actually defined as loss of water with no loss in Sodium. Fluid volume deficit, however, would be a decrease in water AND sodium. Even though these 2 terms should not be used interchangeably, they often are, which can be rather confusing when you actually realize the difference :)

And you're right, vomiting usually loses water AND sodium. So it's actually pretty low-risk for hypernatremia, because it would be more likely to cause fluid volume deficit (not dehydration-review definitions above!). But since the initial poster was asking specifically if vomiting would be more likely to produce hyper or hypo, then I think everyone was responding with that assumption.

But to apply this to the thread's primary discussion, when you lose sodium AND water with vomiting, it's not because sodium is following water, or vice versus. It's simply because it's all just happens to be sitting in your stomach when you upchuck. It might help to visualize it this way. You have a bucket of salt water. You turn it upside down. All of the water and all of the sodium spill out onto the ground. Did one follow the other? No, not really, they both just followed the law of gravity! It's the same with vomiting. One is not really following the other in vomiting, it's just an external force (contraction of diaphragm etc) that causes the stomach to be squeezed, forcing everything that was inside...out.

Thank you.

My professor referred to hypovolemia caused by vomitting as isotonic dehydration, but fluid volume deficit makes so much more sense.

Sorry to have hijacked the thread

[anonymous1919, LPN]

That's actually a very insightful question. And you're right!

Dehydration is actually defined as loss of water with no loss in Sodium. Fluid volume deficit, however, would be a decrease in water AND sodium. Even though these 2 terms should not be used interchangeably, they often are, which can be rather confusing when you actually realize the difference :)

And you're right, vomiting usually loses water AND sodium. So it's actually pretty low-risk for hypernatremia, because it would be more likely to cause fluid volume deficit (not dehydration-review definitions above!). But since the initial poster was asking specifically if vomiting would be more likely to produce hyper or hypo, then I think everyone was responding with that assumption.

But to apply this to the thread's primary discussion, when you lose sodium AND water with vomiting, it's not because sodium is following water, or vice versus. It's simply because it's all just happens to be sitting in your stomach when you upchuck. It might help to visualize it this way. You have a bucket of salt water. You turn it upside down. All of the water and all of the sodium spill out onto the ground. Did one follow the other? No, not really, they both just followed the law of gravity! It's the same with vomiting. One is not really following the other in vomiting, it's just an external force (contraction of diaphragm etc) that causes the stomach to be squeezed, forcing everything that was inside...out.

Thanks. Makes total sense now!:)