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NBME 22 Answers

nbme22/Block 2/Question#14

A previously healthy 12-year-old boy is brought to ...

Glucose and sodium

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submitted by armymed88(29),

Glucose is co-transported into enterocytes of SI via sodium

toxoplasmabartonella  That makes that glucose needs to be given with sodium. But, what about bicarb? Isn't the patient losing lots of bicarb from diarrhea? +2  
pg32  Had the same debate. I knew glucose/sodium was the textbook answer for rehydration but also was wondering if we just ignore the bicarb loss in diarrhea...? +2  
makinallkindzofgainz  @pg32 - Sure, they are losing bicarb in the diarrhea, and yes this can effect pH, but it doesn't matter that much. You're not going to replace the bicarb for simple diarrhea in a stable, but hydrated previously healthy 12 year old. You're gonna give him some oral rehydration with a glucose/sodium-containing beverage. Don't overthink the question :) +  
makinallkindzofgainz  *dehydrated +  

Easiest way to think of this is that this is Gatorade. Sure everyone thinks that sports drinks have glucose for the energy (which is also true) but they also contain sugar because the Na/Glucose co-transporter in the small intestine helps drive electrolyte intake. Without glucose, you don’t pull in sodium nearly as efficiently in the gut and the first makers of the Gatorade formula at UF found that once they gave glucose and electrolytes instead of just water to the football team during practice, they didn’t get as dehydrated and their electrolyte balance was a lot more stable.

Kid probably had cholera -- giving Na+ and glucose takes advantage of sodium-glucose cotransporter thereby replenishing electrolytes and energy.

hipster_do  To add on to the diarrhea kid -- SGLT1 is the Na-glucose symporter and it facilitates movement of water into the enterocytes. Water loves to follow sodium around, I think sodium over other electrolytes purely because sodium is generally the highest concentration electrolyte. +1  

 +1  upvote downvote
submitted by hello(144),

The patient is dehydrated. Need to give water to rehydrate.

Water follows solute. If sodium is added to the solution, water will follow the sodium. Now, enterocyte uptake of sodium is mediated by Sodium-Glucose transporter. Hence, the solution needs to contain sodium and glucose in order to have the enterocytes take up the sodium.

 +0  upvote downvote
submitted by beto(1),

Glucose is co-transported into enterocytes of SI via sodium

Glucose is co-transported into enterocytes of SI via sodium

+/- beto(1),