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NBME 21 Answers

nbme21/Block 1/Question#10

A 34-year-old woman is brought to the emergency ...

Primary metabolic acidosis with increased anion gap

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Na-(Cl-+HCO3-)=anion gap = 140-(105+10) = 25 mEq/L

normal range for anion gap is 8 to 16 mEq/L...Therefore, positive anion gap.

pH = 7.25, normal range 7.35-7.45... Therefore acidosis

Normal bicarbonate 22-28, questions shows bicarb of 10. Therefore metabolic acidosis

Additionally PCO2 normally 33-45 mm Hg, question shows PCO2 of 23 with normal PO2, therefore respiratory compensation

 -1  upvote downvote
submitted by temmy(27),

please help according to winters equation the patient has a normal anion gap

ergogenic22  winter's formula is to look at the compensation to see if it is appropriate. PCO2 = 1.5[HCO3-] + 8 +/- 2 In this case, 1.5* 10 (Pt's bicarb) +8 +/-2 = 21 to 25 Pt's PO2 is 23, so compensation is appropriate. If PCO2 was below 21, it would be concomitant respiratory alkalosis +1  
ergogenic22  in other words, winter's formula is not necessary for this question +1  
the_sacramento_kings  lol unless you want to make sure its not A. +1  
hello  @ergogenic22 Someone might use Winter's formula to rule out choice A. +  
maxillarythirdmolar  respiratory depression of alcohol should rule out "A" +