Why 1/2 normal saline?

Nurses General Nursing

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I'm trying to figure out why 1/2 normal saline would be ordered in my patient? Patient is here for uti and aki. BUN is in the 50-60 range, creatinine 2.5-3. Initial sodium was 131 and is now 136. Saw a note from the doc about continuing diuresis and holding lasix until the creatinine drops. I don't even see lasix or any diuretic in the MAR, but let's just say it is I can't figure the reason for using 1/2 NS instead of NS.

Specializes in Public Health.

Did you ask the Doc?

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Specializes in Emergency Department.
Shoot.... I'm thinking this through, also as a student.

1/2 NS placed in vessels will pull water into the vessels.

If your pt has kidney issues, this may help to provide perfusion to the kidneys, which I think will in turn hopefully prevent kidney failure.

Without perfusion, kidneys will die and then the whole body will have adverse effects.

Am I on the right track, experiences nurses?

Remember, "water follows sodium." 1/2 NS has less sodium than the body usually has... it's hypotonic. So water is going to leave the vessels until the sodium concentration is equal on both sides of the vessel walls.

This patient is slightly hyponatremic but you want to continue diuresis (loss of water). Normal saline in this patient may have a slightly higher sodium content than the blood (and rest of body compartments)... so what happens when you pull water from the blood?

Think about the sodium concentrations here...

I'm no expert in AKI, but if this patient is diuresing for physiological reasons, it doesn't make sense to me to exacerbate it with Lasix (or any other diuretic for that matter) but water replacement will be necessary while this is going on. I would imagine that the doc's got some timed labs (blood and urine) in place for a while to keep close tabs on sodium, potassium, BUN, Creatinine, and the like. Patient probably also is on strict I&O... (particularly output, I'd imagine...)

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Did you ask the Doc?

Not calling the doc at 3am for this one.

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Remember, "water follows sodium." 1/2 NS has less sodium than the body usually has... it's hypotonic. So water is going to leave the vessels until the sodium concentration is equal on both sides of the vessel walls.

This patient is slightly hyponatremic but you want to continue diuresis (loss of water). Normal saline in this patient may have a slightly higher sodium content than the blood (and rest of body compartments)... so what happens when you pull water from the blood?

Think about the sodium concentrations here...

I'm no expert in AKI, but if this patient is diuresing for physiological reasons, it doesn't make sense to me to exacerbate it with Lasix (or any other diuretic for that matter) but water replacement will be necessary while this is going on. I would imagine that the doc's got some timed labs (blood and urine) in place for a while to keep close tabs on sodium, potassium, BUN, Creatinine, and the like. Patient probably also is on strict I&O... (particularly output, I'd imagine...)

I do not think there are any orders for lasix. I am not sure why she charted hold lasix. Pt does have a history of chf though. Labs of course are being followed.

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Specializes in ICU, CVICU, E.R..

What's the Serum Osmolarity of your patient? Check that and we can have a better understanding of the fluids chosen.

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What's the Serum Osmolarity of your patient? Check that and we can have a better understanding of the fluids chosen.

If she's still there tonight I'll look. I'm not at work anymore.

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Specializes in Urology.

Your doc is trying to gently address the hyponatremia by ordering 1/2 NSS. 1/2 NSS will pull sodium into the serum to reach equilibrium it does not pull water like another suggested. Think about this for a second. If we have a 1.5 on one side and 0.5 on another and separate them by a semi permeable membrane the sides will equilize with both sides being a concentration of 1 (equilibrium laws). Should your patient have a critical low sodium a different approach would probably be used (hypertonic saline).

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Specializes in Public Health.
Not calling the doc at 3am for this one.

I would imagine at some point you come across docs at night. I work night shift and I usually see at least ONE doc per shift.

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you need some more PHM to see why because of the diuretic use

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Specializes in Emergency Department.
Your doc is trying to gently address the hyponatremia by ordering 1/2 NSS. 1/2 NSS will pull sodium into the serum to reach equilibrium it does not pull water like another suggested. Think about this for a second. If we have a 1.5 on one side and 0.5 on another and separate them by a semi permeable membrane the sides will equilize with both sides being a concentration of 1 (equilibrium laws). Should your patient have a critical low sodium a different approach would probably be used (hypertonic saline).

Yep. However across a semipermeable membrane, water will cross the membrane to reach sodium equilibrium, sodium will not cross the membrane from high side to low side. Remember, that's why it's said "water follows sodium" because water will go to the higher concentration of sodium until equilibrium is reached.

Now on to another thought: because the patient is diuresing, why didn't the Doc order 1/4 NS?

Serum Osmolarity should also give a good indication of why 1/2 NS. Consider question, what's being protected by continuing the diuresis without adding diuretics to the mix?

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Specializes in Utilization Review.

Whatever doc put in the order should be able to answer it for you. I can't think of a good reason myself, but any time I had a question be it on nights or days I would reach out to get answers. If other nurses didn't have an answer, there were always house doctors some where in the building and we had a hospitalist team right on our floor I could ask as well if they had some down time. Most MDs who are reasonable people will not turn away a nurse who starts a question with "I know you didn't put this order in, but I am concerned for my patient and need to know for future reference." If you do get an answer, please let us know! I'll be curious from now on :)

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I'm trying to figure out why 1/2 normal saline would be ordered in my patient? Patient is here for uti and aki. BUN is in the 50-60 range, creatinine 2.5-3. Initial sodium was 131 and is now 136. Saw a note from the doc about continuing diuresis and holding lasix until the creatinine drops. I don't even see lasix or any diuretic in the MAR, but let's just say it is I can't figure the reason for using 1/2 NS instead of NS.

I did a bit of looking and it looks like the chloride level in NS (which is higher than in plasma) can harm the kidneys, especially if the person's already suffering AKI: Skeptical Scalpel: Is normal saline bad for the kidneys?.

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