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NBME Step 2 CK Form 7 Answers

step2ck_form7/Block 3/Question#16 (reveal difficulty score)
A 16-year-old girl is brought to the ...
Aspirin ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: renal inc

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submitted by โˆ—jlbae(159)

Anion gap metabolic acidosis and compensatory respiratory alkalosis. Only 2 options here are methanol or aspirin. Yea, I guess you could go into Winter's formula and blah blah blah, but just think about it... this is a 16 yo girl trying to kill herself, so pill ingestion is very likely. If it were some alcoholic hillbilly trying to make moonshine I might've thought methanol.

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billasmalls  lol actual sound reasoning...thanks +

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submitted by โˆ—keyseph(99)

Calculated anion gap is 140-(104+6) = 30. This patient has a high anion gap metabolic acidosis.

Based on Winter's formula, adequate respiratory compensation would yield a PCO2 of 1.5*6 + 8 ยฑ 2 = 17 ยฑ2. Since this patient's actually PCO2 was lower, she also has a concomitant respiratory alkalosis.

Since salicylates stimulate respiratory drive and are part of the MUDPILES mnemonic, aspirin is the only answer choice that explains the high anion gap metabolic acidosis with respiratory alkalosis.

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submitted by โˆ—step_prep5(246)
  • Patient who attempted an overdose who has a mixed anion-gap metabolic acidosis (140 โ€“ 104 โ€“ 6 = 30 > 12) with a significant respiratory alkalosis, most consistent with aspirin/salicylate poisoning

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submitted by โˆ—305charlie94(6)

Shouldn't early salicylate OD cause resp alkalosis? I thought only late salicylate OD caused increased anion gap metabolic acidosis. I chose Methanol given her eye sxs and I thought aspirin should be ruled out due to the timing of her OD

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submitted by โˆ—seagull(1933)

THe acid-base status of aspirin is always in the process of shifting from alkalosis to acidosis over a few hours. So relying on ABG is unreliable (in my opinion) for a quick answer.

Rule of thumb for aspirin toxicity: Fast respirations, tinnitus, kidney damage (increased creatinine).

This question she had a fast respiration rate.

---Not perfect but may help in a quick pinch-----

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fkstpashls  Yup, just adding a little bit to this: You can have a normal range pH but expect both primary resp alk and primary met acidosis afterwards to be present, making sure you have an elevated anion gap - if you have questions with the arrow shit to choose from. +

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