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Retired NBME 21 Answers

nbme21/Block 4/Question#44 (reveal difficulty score)
A 28-year-old woman with chronic renal ...
Furosemide ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: renal diuretics GFR

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 +11  upvote downvote
submitted by soscrying(11)
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at my uni, we learnt that at lower GFR, loop diuretics still work. That's why you should use them in renal failure. Thiazides would not work with a GFR of <30.

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qball  Dang, you actually learned something at your school? Lucky. +24
lowyield  At our med school they teach us that Thiazide anti-HTN function is primarily from it's direct effects on vasculature rather than it's diuretic effects. Somehow directly affects the vasculature which is not well understood but this is linked to why Thiazides have greater efficacy in African American Populations. That's kinda why i figured it wouldn't be the best diuretic in this case. +3
brotherimodu  lowyield but interesting +2



 +8  upvote downvote
submitted by โˆ—hungrybox(1277)
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Loop diuretics are first line for acute congestive heart failure. That should help you remember that they are the most potent diuretics, so they're often used in the acute treatment of edema.

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peridot  I think what threw me off was that this lady had such low GFR, figured it couldn't be right. Turns out it's still ok. Furosemide is a miracle drug!! +1



 +3  upvote downvote
submitted by โˆ—mcl(671)
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Furosemide and other loop diuretics are indicated for use in volume overload secondary to renal failure. Recall loop diuretics inhibit the Na+/K+/Cl- pump at the thick ascending loop of Henle, which messes with the hypertonicity of the medulla and therefore prevents urine from being concentrated. This results in increased fluid loss to urine, and is helpful in treating symptoms of edema.

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 +3  upvote downvote
submitted by โˆ—thepromise(66)
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Chronic renal failure = High potassium in blood (page 590 FA19) Furosamide is the strongest diuretic on that list that also depletes Potassium

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claptain  HCTZ and acetazolamide would also deplete potassium, they are just not as strong of diuretics. To be potassium-sparing, it has to have effect at the collecting ducts. Any diuretic that works before the collecting ducts will increase the concentration of sodium going to the collecting ducts and stimulate sodium/potassium exchange at the collecting ducts, potentially leading to decreases in potassium +4



 +2  upvote downvote
submitted by โˆ—ali_hassan(11)
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furosemide is the DOC for fluid over flow (i.e. HF) but i cucked myself by overthinking

CKD = hypocalcemia. furosemide = more hypocalcemia. hydrochlorothiazide = get to keep the Ca2+ babies. chose thiazide with a smile on my face, but didnt last long

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 +1  upvote downvote
submitted by โˆ—basic_pathology(25)
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Loop diuretics are 90% bonded to proteins and are secreted into the proximal convoluted tubule through organic anion transporter 1 (OAT-1), OAT-2, and ABCC4. Thus, there use is not dependent on GFR.

Thiazide diuretics are filtered via the glomerular apparatus, thus their use is dependent on GFR.

Use loops during low GFR states. Use thiazides in normal GFR states (to prevent compensatory Na/Cl reabsorption at the distal tubule when using a loop).

https://en.wikipedia.org/wiki/Loop_diuretic

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