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  #1  
Old 07-03-2011
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Kidney Ca(2+) filtered load

A patient with acute glomerulonephritis has a total plasma Ca2+ of 2.5 mmol/L and a GFR of 160 L/day. What is the estimated daily filtered load of calcium?

(A) 64 mmol/day
(B) 120 mmol/day
(C) 240 mmol/day
(D) 400 mmol/day
(E) 800 mmol/day
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Old 07-04-2011
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Filtered load=GFR x plasma conc.
=160x 2.5=400mmol/day
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Old 07-04-2011
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Default 400

This is one of the "come on.. really?" question.
I read this question and instantly the answer was 400. But I was like hmm noo, may be not. Cant be that beginner of a question. Cos the patient has glomerulonephritis so may be the normal equation of FL does not fit here.
RIGHT??
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Old 07-04-2011
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Idea!

Quote:
Originally Posted by docji View Post
This is one of the "come on.. really?" question.
I read this question and instantly the answer was 400. But I was like hmm noo, may be not. Cant be that beginner of a question. Cos the patient has glomerulonephritis so may be the normal equation of FL does not fit here.
RIGHT??
It is really tricky question, I got it wrong, what why decided to post....
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Old 07-04-2011
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Default ?????

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Originally Posted by jahn77 View Post
It is really tricky question, I got it wrong, what why decided to post....
So whats the answer to this??
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Old 07-04-2011
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Correct Answer Correct answer.

I was going to wait for more options,

OK, here is the trick, taking into consideration that about 40% of total Ca is bound to proteins and can not be filtered;
The answer will be 240 mmol/day. (60% of 400 mmol/day)

Got the question from Lange Qbank book, physio part...
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Old 07-04-2011
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Default

Quote:
Originally Posted by jahn77 View Post
I was going to wait for more options,

OK, here is the trick, taking into consideration that about 40% of total Ca is bound to proteins and can not be filtered;
The answer will be 240 mmol/day. (60% of 400 mmol/day)

Got the question from Lange Qbank book, physio part...
GOOD ONE!!!...
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Old 07-04-2011
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that is a really good question!
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Old 07-05-2011
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The question states Ca2+.......as in free ion, why they would expect you to think that includes non ionic forms bound to protein, is ridiculous and defeats the purpose of a "trick" question. Just a thought.
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Old 07-05-2011
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Originally Posted by moe2185 View Post
The question states Ca2+.......as in free ion, why they would expect you to think that includes non ionic forms bound to protein, is ridiculous and defeats the purpose of a "trick" question. Just a thought.
I thought same way, but the buzzword - TOTAL plasma Ca2+ which consists of bound Ca and free ionic form.
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Old 07-05-2011
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The thing is even with TOTAL being stated it only applies to what comes after that word. If it stated TOTAL serum calcium then sure it would mean ionic and non ionic forms, but if you say TOTAL serum Ca2+ now you are discussing a specific state of calcium.

Nomenclature should be absolute when making questions at this level of education and should not be used as short forms or else it just gets confusing.
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Old 07-05-2011
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Default Ca2+ - albumin binding

Thank you for good point,I looked back to book, guessing my mistype,but it was written as Ca2+ (ionic form), and than, what RR Biochem says:
"Aspartate and glutamate (acidic): negative charge at pH 7. Albumin has many of these acidic amino acids, which explains why it is a strong binding protein for calcium and other positively charged elements". And Ca2+ binds to albumin as ionic form, not any other type, I guess it is Van der Vaals bonds, what why they easily displaced on change of blood pH.
And wiki says about albumin: Albumin is the main protein of plasma; it binds water, cations (such as Ca2+, Na+ and K+), fatty acids...so it is the same ionic form.
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Old 07-20-2011
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Quote:
Originally Posted by jahn77 View Post
A patient with acute glomerulonephritis has a total plasma Ca2+ of 2.5 mmol/L and a GFR of 160 L/day. What is the estimated daily filtered load of calcium?

(A) 64 mmol/day
(B) 120 mmol/day
(C) 240 mmol/day
(D) 400 mmol/day
(E) 800 mmol/day

Nice question. I ran across a similar one in Kap bank:

Testing of plasma shows plasma Ca2+ as 5 mmol/L and GFR as 150 L/day. What is filtered load for Ca2+:

150 L/day
300
369
550
750 -> ANSWER

(I think they missed up the units for the answer choice and should have been mmol / day).

But why it's the answer 40% of the 750 as it was for you problem that you have posted?

One more thing that confused me was that 99% of Ca is bound to bone, 1% in blood and of that 40% is bound, is that correct?
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