Dr.Diplodocus
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Does anybody have a simple way of explaining the different types of hyponatraemia?! So we are supposed to be looking at it in more of a clinical context but need to know the pathophysiology of the various types - hypovolaemic, euvolaemic, and hypervolaemic.
Euvolaemic hyponatraemia is seriously confusing me as all of the textbooks that I've read say that this is effectively a dilution hyponatraemia but that the body sodium level has not altered. I know that SIADH is a cause, but in this context, I assumed that the hyponatremia was (as I've read) dilutional due to the inappropriate reabsorption of water. If this is the case, how is it not hypervolaemic?

Clear as mud what I'm asking? I hope people can understand...much appreciated x
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jumjum
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(Original post by Dr.Diplodocus)
Does anybody have a simple way of explaining the different types of hyponatraemia?! So we are supposed to be looking at it in more of a clinical context but need to know the pathophysiology of the various types - hypovolaemic, euvolaemic, and hypervolaemic.
Euvolaemic hyponatraemia is seriously confusing me as all of the textbooks that I've read say that this is effectively a dilution hyponatraemia but that the body sodium level has not altered. I know that SIADH is a cause, but in this context, I assumed that the hyponatremia was (as I've read) dilutional due to the inappropriate reabsorption of water. If this is the case, how is it not hypervolaemic?

Clear as mud what I'm asking? I hope people can understand...much appreciated x

it is low sodium in blood not low water,


http://www.mayoclinic.org/diseases-c...n/con-20031445
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Dr.Diplodocus
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Yes but hyponatraemia is subdivided into hypovolaemic, euvolaemic and hypervolaemic...?
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Tech
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(Original post by Dr.Diplodocus)
Does anybody have a simple way of explaining the different types of hyponatraemia?! So we are supposed to be looking at it in more of a clinical context but need to know the pathophysiology of the various types - hypovolaemic, euvolaemic, and hypervolaemic.
Euvolaemic hyponatraemia is seriously confusing me as all of the textbooks that I've read say that this is effectively a dilution hyponatraemia but that the body sodium level has not altered. I know that SIADH is a cause, but in this context, I assumed that the hyponatremia was (as I've read) dilutional due to the inappropriate reabsorption of water. If this is the case, how is it not hypervolaemic?

Clear as mud what I'm asking? I hope people can understand...much appreciated x
I think I understand your question.

My two pennies...

Basic facts:
- Aldosterone acts to reabsorb water and sodium in a relatively physiological ratio
- ADH however acts to reabsorb water well in excess of sodium
- ADH can boost your volume state in an emergency eg., blood loss which is why haven't evolved out of it

In SIADH (or other non-osmotic ADH state):
- You would expect to get hypervolemic hyponatremia as explained above
- However your levels of aldosterone will drop to counter the hypervolemia
- Lowering the aldosterone won't change the ratio of salt to water, but will decrease levels of both in roughly equal measures

Hope that helps!
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Dr.Diplodocus
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(Original post by Tech)
I think I understand your question.

My two pennies...

Basic facts:
- Aldosterone acts to reabsorb water and sodium in a relatively physiological ratio
- ADH however acts to reabsorb water well in excess of sodium
- ADH can boost your volume state in an emergency eg., blood loss which is why haven't evolved out of it

In SIADH (or other non-osmotic ADH state):
- You would expect to get hypervolemic hyponatremia as explained above
- However your levels of aldosterone will drop to counter the hypervolemia
- Lowering the aldosterone won't change the ratio of salt to water, but will decrease levels of both in roughly equal measures

Hope that helps!
Yeah, that helps...I thought that it must be linked to the fact that although ADH/osmolality-mediated control has gone haywire, the aldosterone/volume control would kick in. Think it's a 'wood for the trees' situation where I've just been getting too ravelled up with the fine detail and terminology!!
Thank you!
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