0.45% NS is Hypernatremia?

[CBsMommy]

So, I am trying to wrap my head around why we would use 1/2 NS in hypernatremia patients.

Here's what I have worked out so far...

1/2 NS is a hypotonic solution which would cause cells in the blood to swell with water.

The only thing that I could think of would be that this would change osmolarity in the blood thus pulling in water from the interstitial fluid to replace blood volume, which would then dilute the serum sodium level. Am I on the right track?

I've googled and can't seem to find an answer on the cellular level, just that we do use 1/2 NS to correct hypernatremia.

Thanks in advance.

[Mike R, ADN, BSN, RN]

I will ask the teacher tomorrow for further clarification and will let you know. Thanks again for going out of your way to help!

Let us know what it is when you find out! I'm still banking on my first response!

[pippylockstocking]

Someone else may have already said this, but I think it depends too on the patient's fluid volume status. If the patient is hypovolemic then hypotonic solutions are not recommended until the patient is stabilized. Once stable, then hypotonic solutions are appropriate for a euvolemic patient. Hypervolemic patients with hypernatremia are treated with diuretics, etc.

[CBsMommy]

Mike -

You were on the right track and I was totally overthinking it. The answer was this:

If there is too much sodium in the serum of the blood, the cells are already sitting in a hypertonic solution (therefore they are already shrunken down). If we give 0.45% NS, which is a hypotonic solution, it will balance out the serum sodium levels by dilution and cause the cells to swell with water bringing them back to the normal shape. Once we get the sodium stabilized (which will lead to vital signs being stabilized), we will quit the 1/2 NS and, if necessary, will switch to 0.9% NS to bring the blood volume back to normal if deficit.

That makes a whole lot more sense when we actually draw out the cells on a whiteboard but this is what we're doing. Yeah!

Thanks for everyone's help!

[Professor_Mike]

Many hypernatremic states are a result of deyhydration/volume loss. The examples of diarrhea or diabetes insipidus are examples. The goal is to replace volume, so using .9% NS would be just fine until volume is corrected. Then changing over to .45% would be appropriate. Replacing volume initially with .45% saline would not correct volume deficits as well because the volume would leave the vascular space much quicker that an isotonic colloid. The hypernatremia would resolve from dilution.

[CBsMommy]

Many hypernatremic states are a result of deyhydration/volume loss. The examples of diarrhea or diabetes insipidus are examples. The goal is to replace volume, so using .9% NS would be just fine until volume is corrected. Then changing over to .45% would be appropriate. Replacing volume initially with .45% saline would not correct volume deficits as well because the volume would leave the vascular space much quicker that an isotonic colloid. The hypernatremia would resolve from dilution.

That's what I would've though too. I guess it just depends on the situation the patient is in but for the purposes of my class, the instructor said that was one of the first line of treatments although only to get their VS stable. It's a really scary solution to use because if it gets overused, the consequences could be very severe for the patient.

[Professor_Mike]

That makes sense. Stabilize then definitive treatment. I teach that exact process for treatment of DKA. .9 then .45. Look up the water deficit formula. To get a result, you plug in the weight in kg and serum sodium. It tells you how many liters of fluid you need to bring them to a euvolemic state. For a 100 kg person with a sodium of 160, it would take around 6 or 7 liters of fluid.

[kindaquazie]

This is where nurses sometimes falter in my opinion, wanting an isolated, easy answer. The truth is that fluid and electrolyte disturbances are something you will see every day of your nursing career (if you are in a hospital). "Wrapping your head around it" early and completely will make you not only a good nurse, but a stellar healthcare provider. This website http://www.merck.com/mmpe/sec12/ch156/ch156e.html has an excellent description of hypernatremia and its causes and treatment. These are the principles that we were to learn in pre-requesite classes of biology and chemistry, but usually don't. I hope you will take a little time each day to devote to fluid and electrolytes, along with pH disturbances. These two will serve you well in years to come.

[FockerRN]

That's what I would've though too. I guess it just depends on the situation the patient is in but for the purposes of my class, the instructor said that was one of the first line of treatments although only to get their VS stable. It's a really scary solution to use because if it gets overused, the consequences could be very severe for the patient.

What you have to realize is that just about every solution we have is "scary if overused". Little that is done to patients is benign but you have to weigh the costs and benefits. Especially in the critically ill, which I am most familiar with. If treating hypernatremia IV many of the docs I worked with would use D5 because it is essentially free water in the veins. I've never seen them use 1/2NS but it seems that it would have a similar effect and have less effect on a patient's blood sugar. The best way to correct hypernatremia is through free water via DHT or NG. We need to ultimately dilute the high sodium levels in the blood.

One thing to also note is that with crystalloid, in a healthy patient, only about 33% remains intravascular and the 1/2 life is liek 20-30 minutes. So, if a patient gets a lot of fluid (hypo or isotonic) they are going to swell until back near homeostasis. In a sick patient the number drops to 25%, so only 250mL of a liter bag will stay IV.

I also have to agree with kindaquazie. Nursing students begrudgingly trudge through chemistry and biology (if they even take it at all) and are glad when done with physiology. However, these classes are more important ot what you are going to do on a day to day basis than 50% or more of your nursing classes. If you understand the chemistry and physiology behind drugs, disease processes and treatments you can be much more effective.

Nursing schools and nurses do themselves a disservice by not emphasizing these aspects...I will now step down from my soap box and go back to studying opioids and IV induction agents.

[joyouter]

I think this example might help to explain the complexity of Na shifts intracellularly. I found the explanations and sodium regulation system well written. The article has a very clear diagram of how sodium and water work within the

system. Hope it is helpful

Hypernatremia: eMedicine Emergency Medicine

[joyouter]

Just an addition to the discussion. Hypotonic saline -0.45% solutions were used to correct hypernatremia. The problem being the volume needed, and the rapidity of infusion. Hypertonic saline eg. 3% is chosen because of the small volume needed. but it must be carefully, slowly infused, through an infusion pump, with frequent Na serum levels monitored. The most important reason to consider is what is the underlying illness resulting in Na imbalance - and intracellular/extracellular shifts. Cheers

[GA_guy_1971]

The main reason for the 1/2 NS is to avoid correcting the hypernatremia too rapidly when other treatments such as giving the patient water by mouth or administration of D5W (free water since it is broken down into CO2 & H2O) are not options. Rapid correction can lead to permanent neurological damage and, in some cases, even death. This should take place over a number of days and NOT hours.

Hope this helps!

GA PharmD :)

[CarlieChicRN]

F & E hurts my brain. :) Lol