Discussion Board


Registration is recommended, but not required, to use the Nephrology On-Demand Discussion Board.


Welcome Guest 

Show/Hide Header

Welcome Guest, please login or register.

Pages: [1]
 ReplyRSS feed   
Author Topic: electrolytes and water balance
Guest

Posts: 204
Permalink
Post electrolytes and water balance
on: February 20, 2013, 20:45
Quote

What is the mechanism of hyperkalemia in volume depleted state? Thanks.

Guest

Posts: 204
Permalink
Post Re: electrolytes and water balance
on: February 20, 2013, 21:26
Quote

Renal excretion of potassium is primarily through the following mechanisms:
1. delivery of sodium to the distal portion of the nephron (#1 mechanism)
2. urine output
3. action of aldosterone.

In hypovolemic states, there is limited delivery of sodium to the distal portion of the nephron. All the sodium is reabsorbed in the proximal tubule and ascending loop of Henle. As a result, little sodium reaches the distal nephron where potassium can be secreted in return for sodium reabsorption.

Thus, with limited sodium delivery to the distal portion of the nephron, potassium cannot be secreted -----> hyperkalemia.

Guest

Posts: 204
Permalink
Post Re: electrolytes and water balance
on: February 20, 2013, 23:10
Quote

Thanks for your reply...Playing devils advocate here...what about volume depletion causing more angiotensin II and thus stimulating more aldosterone release which in turn cause more stimulation of ENaC causing more secretion of K....This theoretically should cause hypokalemia instead??

Guest

Posts: 204
Permalink
Post Re: electrolytes and water balance
on: February 21, 2013, 06:29
Quote

Great question.

Firstly, I believe aldosterone works on a sodium-potassium/proton channel and not the ENaC channel. The former, I believe, is in the distal nephron and the latter is more proximal to it.

Second, although angiotensin II is elevated in hypovolemic states, causing hyperaldosteronism, aldosterone activity can only work if there is sodium delivered to the distal nephron. Despite elevated aldosterone activity, potassium can only be secreted if there is sodium available for the "swap". This "swap" is mediated by aldosterone but cannot occur independently of sodium.

Guest

Posts: 204
Permalink
Post Re: electrolytes and water balance
on: February 21, 2013, 17:57
Quote

Thank you

Guest

Posts: 204
Permalink
Post Re: electrolytes and water balance
on: February 22, 2013, 12:47
Quote

well, aldosterone actually works on ENaC as well. you have no idea what the hell you are talking about.

But still, I agree with your answers.

Quick Reply:


Enter Security Code: (required)
Pages: [1]
 ReplyRSS feed   
Mingle Forum by cartpauj
Version: 1.0.34 ; Page loaded in: 0.022 seconds.


Share
  • Nephrology On-Demand Plus


    Our full-featured iOS app for the iPhone and iPad. NOD + integrates
    1. kidney education,
    2. training, and
    3. recruitment

    into a streamlined and user-friendly interface.


    Available_on_the_App_Store_(black)

  • Kidney Konnection


    A newsletter that discusses sophisticated topics in Nephrology for physicians in Internal Medicine.
    Click here to access your complimentary subscription