hyponatremia and 3% NaCl

mrsboots87 · Sep 25, 2014

Yes a hypertonic solution can pull fluid from the cells and cause brain shrinkage. But if a patient is hyponatremic, the first line of treatment is oral fluids and possible IV NS. 3%NaCl would only be given in a severe case of low sodium or when the cause is hypervolemia. Also, in low serum sodium, their blood is hypotonic and already pushing fluid into the cells. The risk of cerebral edema comes from giving them too much sodium to where yes, the cells can have fluid pulled from them, but the fluid would also be retained due the sodium. So now they can get edema fluid retention. At least that's how I understand it (I am also still a student so I could have this all wrong lol)

Here.I.Stand, BSN, RN · Sep 25, 2014

The editors of your med-surg book are on crack.

For simple hyponatremia in the med-surg setting, options include oral salt tabs, NS as the IV fluid (as opposed to D5W or 0.45% NaCl), and restriction of free water for drinking.

3% is given to NEURO patients who either have or at risk for high ICPs. Fluid is pulled from the intercellular spaces into the vascular space, reducing cerebral edema and thereby decreasing ICPs. It requires infusion by pump, yes--through a *central line.* At least in my hospital, the patient must be in the ICU to receive 3%. Na levels are monitored q 6 hours to determine that the infusion rate is neither too high nor too low. The neurosurg team determines what their goal Na level is; some patients they just want normonatremia on the high end--140-145. Other times they want it close to 150, or even up to 155.

On occasion, 5% NaCl is used if the 3% isn't doing the job, especially if they are getting fluid overloaded. That way you can then give them the same amount of sodium in less fluid.

2% can be given through a PIV, and in my hospital can be given on the trauma/neuro stepdown unit. Patients on 2% also have Na levels checked q 6 hrs.

If they have ICPs over 20 sustained for over 20 minutes (monitored in the ICU with an extra-ventricular drain), and we need to bring the ICP down QUICKLY, then we can give a dose of 23% NaCl--30 ml given over 15 minutes :)

Here.I.Stand, BSN, RN · Sep 25, 2014

I just slept on this, and decided that a nicer thing to say would be "I don't know why they say this puts a pt at risk for cerebral edema, because that is exactly what we use hypertonic saline to treat." Sorry, I've been on edge the past few days. The risk comes from giving the pt too much, making them hypernatrimic, which can cause seizures (from the shrinkage of the brain cells.) Which is one reason why we check serum Na levels q 6 hours when the pt is on 3%.

Also, it occurred to me that you may not have studied ICP issues yet. If not, here's the basics--

Inside the skull is a fixed space. Inside is filled with brain tissue, blood vessels, and CSF. If any of those increases--from hydrocephalus, bleeding, or cerebral edema--the intracranial pressure increases. So to combat this, the neurosurgeon might put in a drain to monitor the pressure and let some CSF drain off. If indicated, they'll go to the OR and evacuate the clot. Or, we can decrease edema by giving hypertonic saline or an osmotic diuretic like Mannitol. Or, all of the above if it's a severe enough head trauma... then extra sedation, cooling, a neuromuscular blocking drug (paralytic)....... and hope & pray.

Here.I.Stand, BSN, RN · Sep 25, 2014

Oh, and I just wanted to give you props for your critical thinking and asking this question! :up:

You're well on your way :nurse:

Do-over, ASN, RN · Sep 25, 2014

Sometimes, I think they go way too deep for nursing school. Yes to central line and ICU level monitoring for 3%.

icuRNmaggie, BSN, RN · Sep 25, 2014

If you raise the sodium too rapidly the fluid shifts can cause central pontine demyelinosis. Your patient could end up a quadriplegic.

3% sodium chloride is a very dangerous IVF and should be given with great caution and q 4 hour chem 7s.

It should be given through a central line or a very large bore IV.

The goal is to raise the sodium by 0.5 mmol per hour and no more than that.

These patients should be in ICU to be closely monitored for changes in mental status, seizures, CHF and pulmonary edema.

The osmolarity of 3% sodium chloride is 1607 and the pH is 4.5.

Any thing with an osmolarity greater than 600 is known to cause vein damage.

The pH and osmolarity are printed on every bag of IVF.

The quote from the textbook is vague and over simplistic.

The patient should have had a CT of the head for acute change in mental status and cerebral edema would be evident on a CT.

To the OP: why is D5W the worst thing you could give to a pt with cerebral edema?

Here.I.Stand, BSN, RN · Sep 25, 2014

If you raise the sodium too rapidly the fluid shifts can cause central pontine demyelinosis. Your patient could end up a quadriplegic.

You know, I don't remember ever hearing this. You taught me something--thanks! :)

The osmolarity of 3% sodium chloride is 1607 and the pH is 4.5.
Any thing with an osmolarity greater than 600 is known to cause vein damage.
The pH and osmolarity are printed on every bag of IVF.
The quote from the textbook is vague and over simplistic.

I was thinking this too, although I left it at "it needs a central line." It's not a med-surg intervention at all.

To the OP: why is D5W the worst thing you could give to a pt with cerebral edema?

Oh my goodness, a while back one of our 2nd year residents ordered D5W for a TBI admit. It didn't occur to the RN to question this. When the chief resident arrived for rounds in the a.m., she had both their butts on a platter for breakfast. :no:

iluvgusgus · Sep 25, 2014

If they are on 3 percent NaCl they usually have Na levels q 2 or q 4 hours. We usually treat ICPs>20 sustained for 5 minutes, not 20 mintues. If they cant get them down they sometimes order ICPs>25 for 5 minutes call surgeon.

tambarino · Sep 25, 2014

Hi,

I think I actually like you saying that the editors of my book are on crack. It made me laugh. When I asked for clarification for this from my teacher, she just referred me back to the text. Thank you for your help. The information you provided about neuro was really interesting, too!

tambarino · Sep 25, 2014

Yes! This is what I kept reading about online..central pontine demyelinosis. I even asked my teacher about several articles on the topic. Everything I read says the brain will shrink, not swell. Thanks for your input.

Also, the D5W becomes hypotonic after the dextrose is metabolized and will be pulled into the cells increasing ICP and cerebral edema.

tambarino · Sep 25, 2014

I found a rationale that would make my book correct, although it is a more of a rare thing, but still of concern. The rationale was published in the Journal of the Association of Anaesthetists of Great Britain and Ireland.

"Other consequences of hyperosmolarity include acute heart failure and pulmonary oedema from rapid blood volume expansion [11]. In bleeding patients, this rapid volume expansion may theoretically increase the rate of blood loss [36, 89]. A disrupted blood brain barrier may result in a 'reverse osmosis' phenomenon, with worsening cerebral oedema and raised intracranial pressure."

So, pulmonary edema might occur as a result of rapid volume expansion and cerebral edema might worsen in the case of a disrupted blood brain barrier. So, it seems the lesson is that 3% NaCl should be infused very slowly as all of you have mentioned. One, so that desired water shift out of the swollen cells is not too fast and, two, so that the vessels do not fill up too fast.