# Can someone please explain (with calculations) this guyton and hall hyponatremia question answer to me?

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#### creightonstudent101

##### Full Member
5+ Year Member
For the life of me, I cannot figure out the calculation to solve these two problems. Would have been nice if they actually written them out in their answer key!

Thank you!!

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#35
total body fluid: 60% * 60L = 36L
total osmoles before administration = 36L * 260mosm/L = 9360
osmoles added = idk how to do this given their data...but I do know that 1L of 0.9nacl is 154mmol Na, so 2L of 3% is 1026na (and 1026cl) = 2052mosm
total osmoles after administration = 9360 + 2052 = 11412
total liters after admnistration = 36+2 = 38
osmolarity after= 11412/38 = 300.3

#36
ecf osmoles at start = 20% * 60L * 260= 3120mosm
osmoles added = 2052mosm
osmoles at end = 5172mosm
osmolarity from previous = 300mosm/L
ecf fluid after equilibration = 5172/300 = 17.24L

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For the life of me, I cannot figure out the calculation to solve these two problems. Would have been nice if they actually written them out in their answer key!

Thank you!!

View attachment 298623View attachment 298624
Is this Guyton physiology? I would imagine this overkill for the Mcat.

Last edited:
#35
total body fluid: 60% * 60L = 36L
total osmoles before administration = 36L * 260mosm/L = 9360
osmoles added = idk how to do this given their data...but I do know that 1L of 0.9nacl is 154mmol Na, so 2L of 3% is 1026na (and 1026cl) = 2052mosm
total osmoles after administration = 9360 + 2052 = 11412
total liters after admnistration = 36+2 = 38
osmolarity after= 11412/38 = 300.3

#36
ecf osmoles at start = 20% * 60L * 260= 3120mosm
osmoles added = 2052mosm
osmoles at end = 5172mosm
osmolarity from previous = 300mosm/L
ecf fluid after equilibration = 5172/300 = 17.24L
Thank you so much!

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Is this Guyton physiology? I would imagine this overkill for the Mcat.
This is Guyton physiology! And I didn't even realize I posted this in the MCAT study question forum (I meant medical school study question forum!) I hope you had a good admissions cycle and/or good luck in your studies!

This is Guyton physiology! And I didn't even realize I posted this in the MCAT study question forum (I meant medical school study question forum!) I hope you had a good admissions cycle and/or good luck in your studies!
Haha no worries. This totally freaked me out. Good luck to you as well!