Lasix and Hyponatremia

Nurses Medications

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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?

Specializes in Med Surg - Renal.
MN-Nurse,

Could the elevated K be from surgery?

Yep, but if the surgery went OK, I think it's more likely from the cancer or ARF. If the patient is otherwise healthy, I would expect them to respond to the fluid regimen described quite nicely.

@mindlor: alas, no.

hypervolemia in the vascular space doesn't necessarily lower serum na+, because it could be caused by a rapid infusion of normal saline, which, as i described, will have almost no effect on serum sodium, or whole blood, right? remember, "saline is not salt and water" for purposes of thinking about volume.

likewise, hyponatremia caused by too much straight water (like d5w or d5-1/2ns) may not make you hypervolemic, because, as you remember, "saline stays and water travels," meaning that most of that water goes into cells, therefore not sticking around the vacular space to alter any serum electrolytes.

@macunanan, this is why your oliguric patient can be hypervolemic (because he's not making much or soon-to-be-not-any urine) and not necessarily be hyponatremic. he might have a decreased sodium level, especially if he had a period of polyuria (making too mych urine) just before his kidneys feeped out. this is common-- just before they fail, the sometimes become much less efficient at doing their major jobs, namely, reclaiming most of the water from the filtrate and regulating electrolytes.

the kidneys get careless and sloppy, so they let a lot of water out because they can't be bothered to do the work of retaining it, and they can lose a lot of sodium in the process. then when the renal failure really sets in, with oliguria/anuria, there's that low serum sodium sitting there, but it goes back to close to or above the normal range as tine passes and sodium intake (dietary, usually) exceeds renal output (duh, there's no renal output), and it all stays in there resulting in hypervolemia. does that help?

:D ah I see. So its not a mystery at all for me at least. Yes it does help. :) sorry I have so many questions I don't feel comfy just memorizing the labs I need to know what the heck is going on.

:)Thanks again from the bottom of my heart Mindlor and GrnTea

GrnTea, you give the BEST explanations. You should write a book. :)

Thanks. Just finished a chapter in one :)

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