NBME 22 A weak pulse due to decreased stroke volume (NBME Answers)

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Retired NBME 22 Answers

nbme22/Block 1/Question#23 (reveal difficulty score)
A patient in the early stages of hemorrhagic ...
A weak pulse due to decreased stroke volume 🔍 / 📺 / 🌳 / 📖
tags: cardio

+6 upvote downvote
submitted by ∗dr.xx(176)

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Hypovolemia is a direct loss of effective circulating blood volume leading to:

A rapid, weak, thready pulse due to decreased blood flow combined with tachycardia
Cool, clammy skin due to vasoconstriction and stimulation of vasoconstriction
Rapid and shallow breathing due to sympathetic nervous system stimulation and acidosis
Hypothermia due to decreased perfusion and evaporation of sweat
Thirst and dry mouth, due to fluid depletion
Cold and mottled skin (Livedo reticularis), especially extremities, due to insufficient perfusion of the skin

https://en.wikipedia.org/wiki/Shock_(circulatory)

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thrawn Why no sweating? +2

BP/HR are most important to monitor in early stage

Hb starts to drop after 8-12 hours

+4/- dentist(94)

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submitted by joga(1)

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LOW FLOW (HYPOTENSION) ...> LOW SV...> ^SYMPATETIC

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justanotherimg Does this mean that in early stages, sympathetic stimulation hasn't happened yet, that is why pulse is weak ? Because otherwise pulse should be rapid (tachycardia in response to sympathetic stimulation caused by decreased stroke volume). +1

chaosawaits There will be both tachycardia and weak pulse in early hypovolemic shock +

chaosawaits https://www.firstaidforfree.com/how-to-recognise-hypovolemic-shock/ +

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-4 upvote downvote
submitted by ∗atstillisafraud(217)

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Ambiguous question but in because it is early shock, there is not enough time to activate the RAAS to increase kidney perfusion.

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makinallkindzofgainz This is not an ambiguous question. It makes perfect sense. +7

khaleb In early shock you have increased SVR due to vasoconstriction. This would cause increased flow to the kidney. I could be wrong but I think what makes that answer incorrect is NOT that RAAS hasn't been activated yet. It is what is causing vasoconstriction via Angiotensin II. What is possibly wrong about that answer is that it says via sympathetic stimulation. I do think it is a little vague between those two answers though. Because you can get sympathetic activation of the RAAS system causing vasoconstriction and blood shunted to vital organs such as the kidneys. Bottom line is you can't argue with weak pulse during hypovolemic shock.... so an obvious right answer. You could make a case for the increased blood flow to the kidney though. +3

zqatan @makinallkindzofgainz no need to dismiss the question... so pretentious +3

chaosawaits @zqatan, interesting, I thought OP was the pretentious one: to each their own, I suppose +

leap1608 FA2020 PAGE 310 simply focusing on term hemorrhagic shock preload decreases highly which would decrease the stroke volume. early sympathetic system would only increase the heart rate( as cardiac output= stroke vol*heart rate ) +

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