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NBME 20 Answers

nbme20/Block 3/Question#44

A 56-year-old man is brought to the emergency ...

Capillary hydrostatic: increased; Interstitial hydrostatic: increased; Interstitial oncotic: decreased

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submitted by hayayah(244),

LV stopped working, pressure backed up into pulm circuit. Pulm circuit roughly is made of 3 "parts" - the capillaries, interstitial space, and the alveoli.

In cardiogenic shock, the extra blood increases capillary hydrostatic pressure, driving fluid into the interstitial space. Compared to the alveoli, the interstitial space now has more fluid (thus more interstitial hydrostatic pressure and less oncotic pressure due to ratio of fluid to protein), and as a result of this unbalancing of forces, fluid moves into the alveoli --> pulmonary edema.

masonkingcobra  https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Figure%204.1.%20Mechanisms%20of%20enhanced%20transcapillary%20filtration%20in%20response%20to%20elevations%20in%20arterial%20or%20venous%20pressure.&p=BOOKS&id=53445_fig4.1.jpg +  

 +2  upvote downvote
submitted by hello(29),

Patient's symptoms began 30 min after mowing lawn (i.e. after doing physical activity). He has severe chest pain and is cool, clammy, diaphoretic. He has increased pulmonary artery pressure and increased left atrial pressure. Taken altogether, this is cardiogenic shock.

Cardiogenic shock is a heart pump problem -- the LV isn't working.

When the LV, isn't working, it causes a back up in the direction opposite to how blood normally flows. Therefore, blood will back up in the lungs.

This causes increased capillary hydrostatic pressure --> this drives more fluid into the interstitium --> this causes increased interstitial hydrostatic pressure --> there is now more fluid than normal in the interstitium --> this affects the protein ratio within the interstitum --> this causes decreased interstitial oncotic pressure.