NBME 20 Cl<sup>-</sup>: 96 mEq/L; HCO3<sup>-</sup>: 8 mEq/L (NBME Answers)

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Retired NBME 20 Answers

nbme20/Block 4/Question#31 (reveal difficulty score)
A 48-year-old man is brought to the emergency ...
Cl^-: 96 mEq/L; HCO3^-: 8 mEq/L 🔍 / 📺 / 🌳 / 📖
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submitted by ∗hayayah(1212)

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Iron overdose is a cause of a high anion gap metabolic acidosis.

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meningitis I found this to add a little bit more explanation as to how it causes the acidosis if anyone needs it. 1. Mitochondrial toxicity - decreases aerobic respiration and shunts to lactic acid production 2. Cardio toxicity (Secondary to Mitochondrial toxicity) leads to cardiogenic shock (hypoperfusion), which causes lactic acidosis 3. Hepatotoxicity - Decreases lactate metabolism, causing lactic acidosis 4. When in trivalent form (Fe+3), it can react with 3 molecules of H2O --> FeOH3 + 3H+ This will then deplete Bicarb buffering system resulting in non-gap acidosis. Source: https://forums.studentdoctor.net/threads/iron-poisoning-anion-gap-or-non-anion-gap-acidosis.958285/ +20

sympathetikey None of the other choices were even metabolic acidosis. They threw us a bone with this one. +33

imnotarobotbut Don't changes in bicarb take a few days? How did his bicarb drop down to 8 in 12 hours? +2

charcot_bouchard its met acidsis. not compensation +9

j44n they did throw us a bone however I didnt catch it +7

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submitted by manarashour(1)

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regarding my understanding, we are looking for option with high anion gap metabolic acidosis so you will exclude choice A and D because HCO3 high in them, then you will consider Na 140 as they mention in the question it is normal so if you add the cl to HCO3 in option C you will get 134 so it will be normal anion gap so only choice you left with is B.

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