NBME Free 120 Orthostatic hypotension (NBME Answers)

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free120/Block 2/Question#31 (reveal difficulty score)
A 23-year-old woman is brought to the medical ...
Orthostatic hypotension 🔍 / 📺 / 🌳 / 📖
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+6 upvote downvote
submitted by thisquestionsucks(9)

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This question is kinda whack. Right away, I could tell this was exercise-induced collapse, which happens pretty often to runners. I picked autonomic dysfunction because I didn't realize that this is considered an "orthostatic hypotension." After a long race, runners have a decreased SVR from all of the blood flow going to muscles. Once they stop, blood pools, doesn't get back to the ol noodle and they collapse. But ffs I still didn't pick orhtostasis because I think of old people. Fuck me

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step7777 Not to mention orthostatics in the hospital imply a sudden change based on positioning. This patient didn't go from lying down to standing suddenly (just bitter bc I also chose autonomic dysfunction. +3

jbrito718 Hypokalemia would present with muscle weakness. Autonomic dysfxn is a decreased baroreceptor sensitivity so we would not see appropriate correction with elevated feet (over correction/hypertension would be seen). Isotonic saline would not correct hyponatremia, it would probably make it worse (dilution effect). MI would have different symptoms. +2

faili7777 @jbrito718 I think you misunderstood something. People who do marathon are really susceptible to hyponatremia. And the treatment for hyponatremia is literally '0.9% saline' because it is isotonic. So it's used to treat 'hyponatremia' +2

stenebee also chose autonomic dysfunction since I thought orthostatic hypotension had to measured in a much short time interval than 30 minutes apart like this question indicates (85/50 at first, 110/70 thirty minutes after leg elevation/saline infusion). My brain was thinking the repeat measurement would need to be within 1-5 mins for it to be orthostatic hypotension, & per AAFP "Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of standing when compared with blood pressure from the sitting or supine position." ughhhhh :) +

+4 upvote downvote
submitted by ∗lpp06(41)

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I fudged and went with autonomic dysfunction - BUT you can eliminate this option because the body's response to her hypovolemic state is exactly as it should be (increased HR due to decreased baroreceptor stretch). There is no dysfunction

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+3 upvote downvote
submitted by ∗mamast16(4)

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Tough question but 0.9% saline is isotonic and normally used for volume repletion is how I got it

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+2 upvote downvote
submitted by ∗b1ackcoffee(115)

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

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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 +2

blah I thought that orthostatic hypotension was more of a chronic condition, but I fooled myself into believing that. +1

cbreland I completely read over the initial BP measurement and picked the wrong answer (mostly b/c of that). Test in 4 days lets get it! +4

+0 upvote downvote
submitted by ∗freemanpeng(7)

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The key is when her legs up, Bp normal and symptoms free. In contast, When standing up(running), low Bp and syncope. And Low volume is surly the MMC. It's just so weird. "retrospective posture change"??

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+0 upvote downvote
submitted by ∗cassdawg(1780)

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This is a tricky question. The another big point of confusion here is that sweat actually causes a hyperosmotic volume contraction. This occurs because the content of sweat is composed primarily of water more so than salt. With that said, its unlikely that this patient will be hyponatremic. If anything she will be hypernatremic.

-Billy Rubin

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