Correcting Electrolytes

[StickMe]

I've been doing clinicals since May and still have no idea how to correct electrolytes. I have asked my residents on various rotations what guidelines they use to correct the various lytes to which they reply that it is mostly guess work. One chief tried looking it up in various texts in the library for me with no luck.

Can someone please tell me how to actually correct the lytes? How much of what will correct by how much? When I start my Sub-I as well as start my internship, I'd like to have a better idea on how to correct lytes than by mere guessing. Also, if you know of a good website that has this info, a link would be greatly appreciated.

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[deleted109597]

Sodium is pretty hard to correct. Potassium, you just push 40. It it's still low, push 40 more later.
(Kidding, sort of).
Washington Manual gives some good advice.

 

[KidDr]

I've been doing clinicals since May and still have no idea how to correct electrolytes. I have asked my residents on various rotations what guidelines they use to correct the various lytes to which they reply that it is mostly guess work. One chief tried looking it up in various texts in the library for me with no luck.

Can someone please tell me how to actually correct the lytes? How much of what will correct by how much? When I start my Sub-I as well as start my internship, I'd like to have a better idea on how to correct lytes than by mere guessing. Also, if you know of a good website that has this info, a link would be greatly appreciated.

Many hospitals have "standing orders" for electrolyte replacement (usually for K, Mg, and Phos) so that the patient's nurse can just automatically give the needed replacement based on lab values. This is especially helpful in an ICU setting, when lytes are more likely to be deranged. Some places also have separate pediatric and adult electrolyte replacement order sets. I carry a copy of our university hospital's pediatric lyte replacement orders around with me, and use it as a reference when I'm rotating at a hospital that doesn't have standing orders. Like IbnSina mentioned, Na is a whole topic in itself, and often has more to do with volume status than replacement (though not always).

 

[StickMe]

Unfortunately, Ive not seen a standing order form at any of our hospitals. Im less concerned with Na and K and more interested in how to replace Mg, Phos, and Ca.

 

[dpmd]

I used to have this in my peripheral brain, but I can't find it right now. I will look for it, but in the meantime I recommend asking an ICU nurse. At most hospitals they replace electrolytes either with a standard order set or by protocol.

 

[colbgw02]

9 times out of 10 it's superfluous medical intervention. honestly, unless they're symptomatic, having EKG changes, or something of the like, why bother? who - besides an internist - gives a flying crap is someone's magnesium is 1.8 instead of 2? hell, my potassium right now is probably 2.7.

but, since you'll be a mindless slave to the attending for at least several years, here ya go. disclaimer: this shouldn't be taken as gospel. do not use this post as any sort of authority.

1) 10 mEq of potassium for every 0.1 it needs to rise.
2) for mag, give either 2 or 4gm unless they're in renal failure. remember, blood Mg is not a good indicator of total body Mg.
3) for phosphorus, just give 40 mmol of NaPhos or KPhos, depending on which cation is more necessary/less damaging, through the IV. or you can just give them 2 packets of your hospital's favorite PO form of phosphorus with every meal for a couple of days.
4) calcium is rarely repleted once you correct for albumin. you can use PO Os-cal or whatever the local flavor is.
5) sodium is almost always corrected with either giving or withholding fluids. hot salt is only given to severe cases of hyponatremia.

 

[Caffeinated]

I agree, it seems to be a lot of guesswork. The formula I have heard is the 2-3-4 rule, or try to keep Mg around 2, PO4 around 3, and K around 4. As for MgSO4 versus Mg-gluconate, I have no idea which is better. For K, each 10 mEq should raise K by 0.1.

 

[DOtobe]

One thing to always remember when replacing electrolytes:

If the patient is taking PO replace K orally! Runs of K through an IV line are extremely painful.

My first rotation of my intern year was surgery, and I chased electrolytes every single day.

My two cents:
- K - as others have said, 10 mEq for every 0.1 rise.
- Mg - usually 2 gm, sometimes 4. Can also give mag oxide 400 mg, but don't do this if the patient is having diarrhea because it will make it worse.
- PO4 - usually replace as NeutraPhos or NeutraPhosK if they are taking PO, if not, give 30 mMol IV.
- Ca - Ca levels without an ionized calcium are useless. Usually give calcium gluconate 1000 mg IV.

I just finished night float, and it's amazing how sensitive the heart is to electrolyte abnormalities. I had two patients whose rapid A-fib resolved with Mg replacement.

 

[Dr JPH]

Be careful with the K. You can get a quick intra/extracellular flux and have some nasty sine wave EKGs pretty quickly.

 

[StickMe]

Over what period of time do you give these?

 

[SBlanc]

Hey dude -
Like you, I have been on clinics a long time and don't really know how to replace lytes (unlike you, however, I am fine with that as I know it will come in internship). Anyhow I just wanted to add this pearl which no one has yet mentioned:

When replacing K, you must fix a low Mg as well, because the K won't go up if the Mg is also low, no matter how much you give.

Don't ask me why, but people love to pimp on this, in my experience... So if the K is low, check the Mg.

 

[DOtobe]

Over what period of time do you give these?

K can be given at 10 mEq/hr through a peripheral line, and at 20 mEq/hr through a central line. Mg is given 1gm/hr. Ca is 1000mg/1hr. Not sure about PO4 (because I don't have to replace it very often).

 

[Arch Guillotti]

K can be given at 10 mEq/hr through a peripheral line, and at 20 mEq/hr through a central line. Mg is given 1gm/hr. Ca is 1000mg/1hr. Not sure about PO4 (because I don't have to replace it very often).

In the OR we give K faster and we will just give mag and calcium IV push

 

[KidDr]

K can be given at 10 mEq/hr through a peripheral line, and at 20 mEq/hr through a central line. Mg is given 1gm/hr. Ca is 1000mg/1hr. Not sure about PO4 (because I don't have to replace it very often).

For replacement purposes (not in acute situations, like giving Ca for hyper-K):
In peds (not sure about adults, but I'd assume it's about the same), we give IV phos (either as Na-phos or K-phos) pretty slow--usually over 4-6 hours. We give IV K and Mg over 1-2 hours; Ca goes in quicker (~30 minutes I think).

 

[KidDr]

If anyone's interested, here's the dosing guide I use for kids:

For KCl:
-level 3-3.5: 0.25 mEq/kg over 1 hour
-level <3: 0.5 mEq/kg over 2 hours

For Mg sulfate:
-level 1.4-1.8: 0.25 mEq/kg over 1 hour
-level <1.4: 0.5 mEq/kg over 2 hours

For KPhos or NaPhos:
-level 3-3.9: 0.15 mMol/kg over 4-6 hours
-level 2-2.9: 0.25 mMol/kg over 4-6 hours
-level 1-1.9: 0.35 mMol/kg over 6 hours
-level <1: 0.5 mMol/kg over 6 hours

For CaCl:
-typically 20 mg/kg/dose, for either hypocalcemia and/or BP support (in cardiac kids); follow ionized calcium if albumin is low

Remember that once kids weigh a certain amount, you're better off just using adult replacement dosing.

Also remember to re-check levels at some point after replacement (K+ usually 30-60 minutes after replacement is given, Mg 1 hour after--if you're really concerned about it and think it might need to be replaced again--or the next morning if you're not as concerned, and Phos typically the following morning)

These are just guidelines, the patient population matters. You're obviously not going to be replacing every kid with a phos of 3.5 or K of 3.2; on the flip side if you've got a post-op heart kid on a Bumex drip, you're probably going to be checking K+ and replacing every few hours.