Jacked Up Sodium

I've only been a nurse for a year, so maybe some of y'all with more experience can help me out here.
I had a patient this weekend with a jacked up sodium level, and I can't figure out what caused it.

This elderly lady was at a party and fell face flat. They rushed her to the ED, did CT scans, X-rays, all that good stuff. She fine (in pain, but no fractures, etc). They could find no reason to admit her, so as they were discharging her, she became dizzy and dang near fainted. Just then they got the results back from her BMP and said, "Oh looky here, her sodium is 120, lets go ahead and admit her.". So they give her a 500cc NS bolus and sent her up to my med-surg floor with an IV of NS going at 100ml/hr.

Her BMP was rechecked in the AM, roughly 6 hours later..... Her Sodium was 119. My only response was "What the ----?, How the heck can that happen?". (Strangely enough, with the low sodium, she was still alert and oriented, no confusion at all).

I called her doc and got the following orders: Recheck BMP in 8 hrs, place on 900cc/24hrs fluid restriction, stop the NS and start 3% NS in 100ml bags at 33ml/hr.

Over the next day and a half her sodium came up to 128, the 3% NS was decreased to 15ml/hr. Then it was 131. Her IV was hep locked and she was kept on the fluid restriction. The last day I worked it was 132. The doc didn't want it to go up too fast. I left work to start my days off so I don't know what ever happened to her.

My question is....How the heck could her sodium get lower after a bolus and being on regular fluids for 6-7 hours? At first I thought the lab screwed up, especially since she wasn't confused (She was 85). This has been naggin me all weekend.
Normal saline is isotonic, it doesn't really increase sodium a whole lot, nor does it really cause fluid shifts. For a Na+ as low was 119-120, you definitely wanted the fluid restriction, slow replacement with 3% and/or diuresis if she's fluid overloaded (?from heart failure?). I'd want to know if it's dilutional or truly that low, then I'd want to know why.I would probably want a BNP! Then again, I am a cardiac nurse so I can't help seeing heart failure everywhere...

Quote from OutlawNurse86My question is....How the heck could her sodium get lower after a bolus and being on regular fluids for 6-7 hours? At first I thought the lab screwed up, especially since she wasn't confused (She was 85). This has been naggin me all weekend.

Is BMP- basic Metabolic panel?If so that is very close to BNP( brain natriuretic peptide ) which shows if your heart is working harder than normal as would happen in CHF.

Did they check her for Syndrome of Inappropriate Antidiuretic Hormone Hypersecretion (SIADH)? That can cause low sodium.

Gila, I bet you are a chemistry whiz! I cant even remember what moles are, much less the formula. Im impressed! However I do understand how 0.9 NS wouldnt increase Na+ and so forth. But I wish I could remember what I learned in my chemistry class years ago.

Quote from OutlawNurse86My question is....How the heck could her sodium get lower after a bolus and being on regular fluids for 6-7 hours? At first I thought the lab screwed up, especially since she wasn't confused (She was 85). This has been naggin me all weekend.

Quote from batmikIs BMP- basic Metabolic panel?

She is 85. She has to be fully worked up for all sorts of disease processes especially brain and kidneys, including her PMHX w/meds.I'm still not over the statement where they were ABOUT to release her until she passed out again...and the BMP hadn't even come back?Am I reading that correctly?

Quote from JoPACURNI'm still not over the statement where they were ABOUT to release her until she passed out again...and the BMP hadn't even come back?Am I reading that correctly?

Quote from chenoaspiritGila, I bet you are a chemistry whiz! I cant even remember what moles are, much less the formula. Im impressed! However I do understand how 0.9 NS wouldnt increase Na+ and so forth. But I wish I could remember what I learned in my chemistry class years ago.

Mmmm, avocados!

I am soooo not smart enough to be reading this thread.