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#1
06-06-2011
 USMLE Forums Guru Steps History: Step 1 Only Posts: 343 Threads: 127 Thanked 525 Times in 192 Posts Reputation: 535
Anion gap question

A 30 year AIDS male pt is admitted in hospital with severe diarrhea. He has protracted diarrhea for past 3 days.
he appears to be breathing rapidly. pulse is thready and fast.
arterial blood sampling is shown below

arterial CO2 = 28 mmHg
arterial pH = 7.32
plasma cl- = 116 mEq/L
plasma HCO3- = 14 mEq/L
plasma Na+ = 140 mEq/L
plasma K+ = 3.4 mEq/l

What is anion gap in this patient..

a) 5
b) 10
c) 15
d) 20
e) 25

I think due to diarrhea there is no anion gap and answer is (B)

but if we calculate according to equation

Na+ = cl- + HCO3-

It turns out to be 13

What u guys think of it?
 The above post was thanked by: pass7 (06-06-2011)

#2
06-06-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,175 Threads: 38 Thanked 854 Times in 478 Posts Reputation: 864

I think the answer is B) 10

The calculation was

Na - (Cl + HCO3):

140 - 130

= 10

You can add potassium to this, but Fish says not to.
 The above post was thanked by: bebix (06-06-2011), doc_study (06-06-2011), drnirajmavani (06-07-2011), JBerger (06-06-2011), pass7 (06-06-2011), sandy_presto3 (06-06-2011), struggle (06-07-2011)
#3
06-07-2011
 USMLE Forums Scout Steps History: Not yet Posts: 13 Threads: 3 Thanked 4 Times in 4 Posts Reputation: 14
it,s B

may be you make something wrong

#4
06-07-2011
 USMLE Forums Scout Steps History: Not yet Posts: 70 Threads: 5 Thanked 13 Times in 10 Posts Reputation: 23

The formula is super clear. Just apply numbers and thats all. Normal anion gap from 8 to 12....so patient has normal anion gap.
#5
06-07-2011
 USMLE Forums Newbie Steps History: Not yet Posts: 9 Threads: 0 Thanked 5 Times in 5 Posts Reputation: 15

it's better not to make it 13 anyways, because the patient had diarrhea and hyperventilation, non of which is associated with increased anion gap!
 The above post was thanked by: bebix (06-07-2011)
#6
06-07-2011
 USMLE Forums Newbie Steps History: 1 + CK Posts: 7 Threads: 4 Thanked 3 Times in 3 Posts Reputation: 13
this is your formula

Hey anion gap is the anionic gap and then the equation is anion gap= Na+ (Cl - CO3) the right choice is 10

Last edited by ari2003; 06-07-2011 at 05:53 PM.
 The above post was thanked by: melboghdady (06-03-2013)

 Tags Physiology-, Renal-, Step-1-Questions

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