Diuretics - volume contraction

[Phloston]

With diuretic-use, is the volume loss considered hypertonic?

More specifically, I'm just trying to solidify in my mind the ECF/ICF changes concomitant with the different diuretics.

I'm 80% sure (can't remember completely) that in Addison's, there is hypotonic volume contraction, which indicates that K+ sparing diuretics generally result in hypertonic losses.

However what about loops/thiazides?

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[Big Baller]

I think it is safe to assume that it would be hypertonic loss with all the diuretics for the purposes of Step1.
Look at RR Path Pg 57.

 

[Phloston]

I think it is safe to assume that it would be hypertonic loss with all the diuretics for the purposes of Step1.
Look at RR Path Pg 57.

That's probably the first use I've gotten out of that book (it's been sitting on my shelf and I've never really looked at it). Thanks for that.

 

[Melkor]

Just a quick question to add to this. As RR does show loops give the hypertonic loss, I thought I remember seeing somewhere that loops also give an isotonic urine (Clearance of h2O=0). Could anyone explain why/how this could happen?

 

[loveoforganic2]

GT says isotonic urine for loops. I rationalized it as you're eliminating the hypertonic medullary interstitium that drives water reabsorption beyond the proximal tubule

 

[Phloston]

GT says isotonic urine for loops. I rationalized it as you're eliminating the hypertonic medullary interstitium that drives water reabsorption beyond the proximal tubule

GT is wrong on so many levels it's not even funny. I had gone through their QBank and had annotated stuff into my FA only to have now encountered UWorld info that is entirely different or contradictory at times.

P. 57 of Goljan says hypertonic losses due to Loops. That definitely overrides GT.

That being said, nothing against their flashcards. I'm aware people have gotten 270+ using their program. I'm just talking about their lousy QBank.

Just a quick question to add to this. As RR does show loops give the hypertonic loss, I thought I remember seeing somewhere that loops also give an isotonic urine (Clearance of h2O=0). Could anyone explain why/how this could happen?

Loops abolish the interstitial electrolyte gradient, making ADH less efficacious, thereby decreasing free-H2O reabsorption. This is a secondary occurrence, but is not intrinsic to the loop diuretic itself, which is instead an inducer of hypertonic loss.

 

[Myxedema]

Guyton & Hall Textbook of Medical Physiology, 12th Edition, p. 395:

By blocking active sodium-chloride-potassium co-transport in the luminal membrane of the loop of Henle, the loop diuretics raise urine output of sodium, chloride, potassium, and other electrolytes, as well as water, for two reasons: (1) they greatly increase the quantities of solutes delivered to the distal parts of the nephrons, and these act as osmotic agents to prevent water reabsorption as well; and (2) they disrupt the countercurrent multiplier system by decreasing absorption of ions from the loop of Henle into the medullary interstitium, thereby decreasing the osmolarity of the medullary interstitial fluid. Because of this effect, loop diuretics impair the ability of the kidneys to either concentrate or dilute the urine. Urinary dilution is impaired because the inhibition of sodium and chloride reabsorption in the loop of Henle causes more of these ions to be excreted along with increased water excretion. Urinary concentration is impaired because the renal medullary interstitial fluid concentration of these ions, and therefore renal medullary osmolarity, is reduced...

 

[loveoforganic2]

Thanks for the citation Myx - it's nice when your rationalizations turn out to actually be the case!

 

[Melkor]

Thanks guys!