nbme 6 block 1 help please - backtobooks

[ArchivalUser]

hi,
ive spent the entire day trying to get explanations for my wrong answers on nbme 6 but sometimes the answer key does not correspond to the question number (are the questions generated in a different order in the online version?) and I seem to not understand the most basic of concepts - seems like my brain cells are shutting down as my exam dat approaches! so if anyone could help me with explanations... sorry am not typing entire questions - just the relevant parts..

q 4 - I feel really dumb asking about this one - infusion of 2 l isotonic saline, no urine excretion, ecf volume increases by how much?
0.3
1
1.3
1.7
2


q 12 - occlusion of IVC above renal veins - increased venous pressure in which vein -
ext iliac
hepatic
inf mesenteric
portal
splenic

[ArchivalUser]

For Q4 ...u are infusing isotonic fluid ...hence no change in osmolarity....but there is change in volume and the change in volume is distributed equally in ECF and ICF(BASED ON THEIR PROPORTION)

..--- u remember 2/3 OF OUR FLUID IS intracellular and 1/3 of our fluid is ECF ....hence 1/3 of the 2L isotonic fluid goes to the ECF ..the rest goes to the ICF ....1/3 * 2L=.667...check again the question

for q12...any vein below the renal vein is gonna get an increased venous pressure...and renal vein joins the IVC at the L1 level hence any vein below L1 ...

external iliac vein is below L1..will get the increased venous pressure

[ArchivalUser]

That's the problem yeahbiruh 0.67 is not one of the choices. :-(

[ArchivalUser]

sorry it is misunderstanding.....the whole isotonic fluid stays inside the ECF ...no net movement between the ECF and the ICF as there is no change in the osmolarity....hence 2L ...forget my previous wrong explanation.....

[ArchivalUser]

sorry I misunderstood the question...when we infuse An isotonic fluid the whole fluid stays in the ECF as there is no change in the osmolarity...recall if there is no change in osmolarity there is no net movement of fluid between the ICF and ECF compartments...hence 2L will be the answer..sorry for the previous wrong explanation...

[ArchivalUser]

I thought the same for the fluids question but yeabiruh's second explanation is correct, all into the ECF and since there's no osmolarity difference, it will stay in that compartment.

As for the latter question, I'd think the external iliac, it's the only one that feeds into the IVC.

[ArchivalUser]

Thank you!