Lasix and Hyponatremia

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I had a patient who's morning labs came back with K 5.0 and Na 127. The patient had been getting D5 1/2 NS all night at 125 cc/hr and urine output was about 30-40 cc/hr. I was concerned for fluid overload and suspected the fluids might've been responsible for the low sodium as well. The resident rounding wrote for lasix 40 mg IVP as well as fluids to be changed to D5 NS at 75 cc/hr. I thought it was okay at first, but now that I'm home I can't stop wondering what that might do to his sodium. I can't find any concrete numbers on how strong of an effect lasix has on sodium. Any thoughts, resources, ideas?

yep, if that helps you to think about how they work. it's not really useful to think of them as hypertonic "in the bag," because that's not where they are going to be. :D

Specializes in Med Surg - Renal.
As far as I know he had no renal problems, Cr was normal, I don't remember what his BUN was. Vital signs were stable, pressures 130s-140s.

As for the fluids, I have no idea, I got a very confusing report. He was post op day 1 for a cancerous mass removal of his lung.

No reason to mention the cancer in your OP I suppose....that could be another factor in the low Na. Cancer can cause all sorts of heck with electrolytes.

In any case, I still strongly suspect from the K, Na, and low UOP that the patient has some acute renal failure (most likely pre-renal) that is being addressed by the fluids with no further intervention. If left alone, the Cr would probably be trending up. The fluid and lasix regimen prescribed is most likely not going to dangerously affect the Na levels.

It would be interesting to hear some follow up.

Thanks!

I think that's where some confusion comes from though, because if you look at the osmolarity of D5 NS, it is hypertonic. That's not taking into account how it behaves within the body.

MN-Nurse,

Could the elevated K be from surgery?

That was very informative GrnTea, thank you for that.

His Na had been 130 in the previous day's labs and I suspected the high rate of D5 1/2 he was given would worsen that. I don't believe the cancer played a role in his electrolyte imbalance, but I can see how certain cancers could do that. I'm not certain why his K was 5, it had been 4.4ish the day before. I have heard that the anesthesia medications can temporarily shut down the kidneys and it takes some time for them to get going, but I don't have have any sources on that.

I also found this a nice read Diuretic-induced hyponatremia

GrnTea Great explaination! I hope you dont mind I have a questions. :D maybe a dumb one, maybe the answer to my question is already answer with your previous post (if yes please just tell me to read your previous post again) but anyway my question is: In Acute Renal Failure, oliguric phase patient have hypervolemia but according to Saunders pt might have normal or decrease serum sodium level....why is that? I thought when theres hypervolemia the serum sodium is suppose to be elevated. :mad: I really wish I paid more atention when I was in school. :D

Oh my gosh grntea!! You are spot on!! I will blame my error on complete brain fatigue secondary to studying for and taking the NCLEX lol. What I said would sounded great for 2% NS lol. Thank you for correcting me ;)

Hypervolemia = too much fluid in the intravascular space. This has a dilutional effect on the serum sodium. This is manifested by a decreased serum sodium level.....

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
that was very informative grntea, thank you for that.

his na had been 130 in the previous day's labs and i suspected the high rate of d5 1/2 he was given would worsen that. i don't believe the cancer played a role in his electrolyte imbalance, but i can see how certain cancers could do that. i'm not certain why his k was 5, it had been 4.4is the day before. i have heard that the anesthesia medications can temporarily shut down the kidneys and it takes some time for them to get going, but i don't have have any sources on that.

i also found this a nice read diuretic-induced hyponatremia

:yeah: another stellar explanation grntea!!!!!! :yeah:

c.e...... but the cancer very well could have caused his low na.....as grntea said,

"he's retaining water, and his na+ is called "dilutional" because all those little na+s are floating around in too much water. some degree of siahd is actually pretty common--- you can do it with anesthesia, mechanical ventilation (there's stretch receptors in the lungs, see, and....oh, later), and a host of common meds"

and the patient has just had a lung resection and anesthesia. as stargazer said "even though there is some sodium loss with the last, the patient is losing more water in proportion, which will increase the serum sodium concentration." so the lasix would help to further "dehydrate" or remove excess water thereby "dehydrating" the patient causing the increase in serum na.

this patient is elderly and very well may take some time to "re-regulate" himself...yes there are anesthesia meds that can cause transient changes to serum 'fluid/electrolytes as well as the stress to of the surgery itself, what and how much ivf were given during the or to the patient? will all reflect in the patients post op lab work.

before i would say this patient has renal issues other than being elderly...i would make sure the k was not hemolyzed and what the bun cr. are doing on trend. mild bump on labs need correcting but do not necessarily indicate renal insufficiency or failure.

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
GrnTea Great explaination! I hope you dont mind I have a questions. :D maybe a dumb one, maybe the answer to my question is already answer with your previous post (if yes please just tell me to read your previous post again) but anyway my question is: In Acute Renal Failure, oliguric phase patient have hypervolemia but according to Saunders pt might have normal or decrease serum sodium level....why is that? I thought when theres hypervolemia the serum sodium is suppose to be elevated. :mad: I really wish I paid more atention when I was in school. :D

Read Grntea'spost again......as minlor said, Hypervolemia = too much fluid in the intravascular space. This has a dilutional effect on the serum sodium. This is manifested by a decreased serum sodium level.....

Thanks Mindlor and Esme12.. I will read Grnteas post again. Drill it in my head :D I just get confuse because in diuretic phase According to Saunders there is hypovolemia and hyponatermia this makes sense to me more. You guys are awesome. I love this site so much. Thanks. I will read the post again. :)

remember that if someone is in a diuretic mode they may actually be excreting too much sodium. This may also cause the pt to become hyponatermic. Remember there are two different modes. Dilutional and actual hyponatermia. The first is corrected by pulling off fluid, the latter by adding sodium.

Take addisons disease for example...low aldosterone so the body is losing sodium AND water. This pt may actually need sodium supplementation......

Also, when worrying with sodium remember that sodium and potassium are usually inversely related. Low sodium typically = high potassium so be vigilant for high K+ and disrythmias.....

What to do for sky high K+? Insulin to tempoarily drive K+ into the cells.....then perhaps kayexelate to actually remove excess potassium.......i was recently taught it is a nice nurse who alerts the CNA prior to giving kayexelate hehe.

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