Saline

[hyrule]

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What are some of the important rules to follow with patients w/ dehydration/various forms of fluid loss? (ones to know for the USMLE)
or even some of the mistakes physicians often make

One scenario I can think of is:
if patient has hypotonic fluid loss and low BP --> giving them regular saline will normalize BP but will not correct dehydration.

 

[bambi]

What are some of the important rules to follow with patients w/ dehydration/various forms of fluid loss? (ones to know for the USMLE)
or even some of the mistakes physicians often make

One scenario I can think of is:
if patient has hypotonic fluid loss and low BP --> giving them regular saline will normalize BP but will not correct dehydration.

You replace like with like.

 

[ArcGurren]

What are some of the important rules to follow with patients w/ dehydration/various forms of fluid loss? (ones to know for the USMLE)
or even some of the mistakes physicians often make

One scenario I can think of is:
if patient has hypotonic fluid loss and low BP --> giving them regular saline will normalize BP but will not correct dehydration.

This is actually absurdly simple.

Hypotonic fluid loss = replace with hypotonic fluid

Hypertonic fluid loss = replace with hypertonic fluid

etc.

Logically if you had someone with hypotonic loss they'd have a higher osmolarity but dehydrated so they have a low BP; if you give them isotonic fluid it'll correct the fluid loss but they could end up with hypernatremia or something to that effect.

 

[mastamark]

What are some of the important rules to follow with patients w/ dehydration/various forms of fluid loss? (ones to know for the USMLE)
or even some of the mistakes physicians often make

One scenario I can think of is:
if patient has hypotonic fluid loss and low BP --> giving them regular saline will normalize BP but will not correct dehydration.

If you dump a ton of free water and end up hypovolemic and hypernatremic, you want to correct the volume first with isotonic sol'n 0.9% saline. You can get 3rd spacing if you give hypotonic solution before correcting volume. Once that's done you can correct the water(hypotonic sol'n).

If they have euvolemic hypernatremia, it can usually be treated with water by mouth or hypotonic solution, but I think they usually just increase drinking to allow the body to do it's thing.

If there is high volume along with your Hypernatremia which is usually from Hyperaldo you can give diuretics and fix the issue.

 

[SlaveOfTCMC]

This is actually absurdly simple.

Hypotonic fluid loss = replace with hypotonic fluid

Hypertonic fluid loss = replace with hypertonic fluid

etc.

Logically if you had someone with hypotonic loss they'd have a higher osmolarity but dehydrated so they have a low BP; if you give them isotonic fluid it'll correct the fluid loss but they could end up with hypernatremia or something to that effect.

To OP: Yep, this is all you need for Step 1. Maybe familiarize yourself with those Yannet Darrow diagrams.


A sidenote: every doctor tells me that although the "like replace like" is true, often times, they just grab 0.9% saline with 5% dextrose and just give that to any patients because "it is readily available."

 

[turkeyjerky]

This is actually absurdly simple.

Hypotonic fluid loss = replace with hypotonic fluid

Hypertonic fluid loss = replace with hypertonic fluid

etc.

Logically if you had someone with hypotonic loss they'd have a higher osmolarity but dehydrated so they have a low BP; if you give them isotonic fluid it'll correct the fluid loss but they could end up with hypernatremia or something to that effect.

Um, no.

That might work for first year physio, but by this stage of the game you should have at least some concept of hemodynamic instability. If someone comes in w/ hypotension from hypotonic fluid loss, they get isotonic saline til they're BP normalizes. Always remember your ABCs on usmle and shelf exams.

 

[ArcGurren]

Um, no.

That might work for first year physio, but by this stage of the game you should have at least some concept of hemodynamic instability. If someone comes in w/ hypotension from hypotonic fluid loss, they get isotonic saline til they're BP normalizes. Always remember your ABCs on usmle and shelf exams.

Um, yes. The gist of what I wrote is still correct; however you're right about the fact that you correct BP with isotonic saline first, my bad.

This is not a particularly high yield step 1 topic anyway, I've rarely seen questions about fluid replacement.

 

[hyrule]

So if you give isotonic infusion (0.9%), it won't enter the ICF but it will spread out over over plasma and interstitium with a 1/4 (plasma) and 3/4 (interstitium) distribution right

 

[ArcGurren]

So if you give isotonic infusion (0.9%), it won't enter the ICF but it will spread out over over plasma and interstitium with a 1/4 (plasma) and 3/4 (interstitium) distribution right

Yes. It stays in the ECF compartment