NBME Answers : Block 2 : #31 = A 23-year-old woman is brought to the medical tent ...

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submitted by b1ackcoffee(8),

confused why this is not autonomic dysfunction or hyponatremia due to sweating and why is this orthostatic hypotension?

mdmofongo This one is tricky and come downs to choosing the “best” option. I can see why you were confused. However do note that in an autonomic dysfunction you will never present tachycardia as this patient does. I guess the key here is seeing how her BP normalizes once she is laying down? Sorry, this one is a kinda unusual presentation of Orthostatic hypo. +

mamed Not sure if this is correct thinking but how I got this right was: 1. She is hypovolemic 2. Likely retaining salt so water follows (ADH or just renal dynamics in general). This is how I ruled our hypokalemia and hyponatremia 3. If she is hyponatremic b/c sweating then why wouldn't she also be hypokalemic? so both have to wrong because both can't be right 4. Volume depletion ==> orthostatic hypotension +