How bolus infusions of NaCl may affect low sodium levels...?

So, the other day in clinical I had an elderly patient who had low sodium levels and low blood pressure. They gave the pt two bolus infusions of NaCl to help get his/her bp back up, and afterward my instructor asked me a few questions about the effects of giving boluses of NS NaCl to someone who already has low sodium levels. The instructor said that giving those boluses would dilute the sodium levels in the pt even further, causing his/her [Na+] ratios to drop. For some reason, I'm having a really hard time believing that. My reasoning:

1) NS NaCl concentrations are based on regular sodium levels. So, if you have a pt who has lower-than-normal sodium in his/her system, then the NS solutions are hypertonic to the pt's Na+ solutes, and that should cause there to be an increase in [Na+] ratio levels, right?

2) Also, even if the pt's Na+ levels were average, shouldn't the 0.9% NaCl solution not dilute the sodium in the pt's system?

I'm just having issues with this because to me it does not logically follow. What do you all say? Am I mistaken or is my instructor?
I am assuming these are IV infusions?Add intravascular sodium = water flowing from interstitial space into the plasma. This = great blood interstitial volume = more urination if the kidneys are functioning, which is going to have them peeing more and thus dropping their serum Sodium further.....

Even if everything is isotonic and osmosis is not a factor, just the virtue of the added fluid volume will equal more excretion which will equal sodium leaving the body.....

I probably said that all wrong. here is a link to a much more astute expanation LOL...http://www.globalrph.com/hyponatremia.htm

To raise levels the pt should be on 2% or3% (central line only) hypertonic saline.

Quote from nrsang97To raise levels the pt should be on 2% or3% (central line only) hypertonic saline.

So, the other day in clinical I had an elderly patient who had low sodium levels and low blood pressure. They gave the pt two bolus infusions of NaCl to help get his/her bp back up, and afterward my instructor asked me a few questions about the effects of giving boluses of NS NaCl to someone who already has low sodium levels. The instructor said that giving those boluses would dilute the sodium levels in the pt even further, causing his/her [Na+] ratios to drop. For some reason, I'm having a really hard time believing that. My reasoning:1) NS NaCl concentrations are based on regular sodium levels. So, if you have a pt who has lower-than-normal sodium in his/her system, then the NS solutions are hypertonic to the pt's Na+ solutes, and that should cause there to be an increase in [Na+] ratio levels, right?2) Also, even if the pt's Na+ levels were average, shouldn't the 0.9% NaCl solution not dilute the sodium in the pt's system? I'm just having issues with this because to me it does not logically follow. What do you all say? Am I mistaken or is my instructor?

As others have said, it depends on the underlying issue. In my line of work, hyponatremia is usually related to an underlying endocrine disorder (SIADH or Cerebral Salt Wasting). In SIADH, you would never bolus to raise serum sodium as the inappropriate levels of circulating ADH would cause the kidneys to retain the fluid thereby possibly dropping the sodium level even more. In Cerebral Salt Wasting, I have given NS boluses to raise serum sodium with good results (123-129-131) throughout the course of the night. In this case, you would use standing NaCl supps to maintain normal sodium levels. In the case of SIADH, you would use fluid restriction.

Quote from mindlorEven if everything is isotonic and osmosis is not a factor, just the virtue of the added fluid volume will equal more excretion which will equal sodium leaving the body.....

Great thread! Not to derail the thread, but here's a link to CPM and "Locked in Syndrome." It results most commonly from raising NA+ too rapidly in patients with chronic hyponatremia.Locked in Syndrome will leave you with your cognition intact, but completely paralyzed except for the ability to blink your eyes, and may be permanent. Frightening.http://en.wikipedia.org/wiki/Central...e_myelinolysis

What exactly was the sodium level, if it is mild the NS boluses aren't going to matter. The body will adjust to the intake of fluid and assuming the kidneys are working normally will retain some of the NA. Isotonic fluid boluses are fine to raise BP in the short term, but unless the patient is dehydrated the majority of isotonic IV fluid is only going to stay in the intravascular compartment for about 20mins.

Quote from nrsang97To raise levels the pt should be on 2% or3% (central line only) hypertonic saline.

It def depends on HOW LOW the pt.'s Na+ is, but usu. NS is enough to raise [Na+] to a normal level.