Med. calc & mEq

chare · Apr 11, 2014

Why don't you show us what you have. This will allow us to see where exactly you're having a problem.

Boxer Mama · Apr 11, 2014

I have shown you what I have with setting up the "order" and "have." I am just not sure where to go from there. I am confused about what values are used and where they are used to solve the problem.

Boxer Mama · Apr 11, 2014

I got it. This is solving for how many mls you would put into the bag of D5W, which would be 5.

Esme12, ASN, BSN, RN · Apr 11, 2014

There you go! See you got it!

Well done!

nurseprnRN, BSN, RN · Apr 17, 2014

Well, you'd put it in a smaller bag, but the question as you give it here is only asking you about the amount of KCl you'd draw up into the syringe. The 500cc bag is extraneous information. If the prescription is to give 2mEq, that's 1cc. The problem as given does not say to give 500cc of a solution of 2mEq per 100cc, does it? If it did, that would be 5cc ... But it doesn't.

If the prescription was for IV fluids with 2mEq/100cc to be given continuously, that's a different matter. In that case, you'd put the 10mEq in the 500cc bag and run it at whatever rate was specified.

ready4nu · Apr 17, 2014

I would start out by figuring out how many mEq per mL I have for the ordered and on hand.

But I am no math whiz and often make things more complicated than they need to be.

RayBIV · Apr 21, 2014

Hi Boxer Mama,

I know you solved it already, but I will reinforce what you did to solve. I am currently in Medsurg and we also use Dimensional Analysis for everything we do. 1) What are you solving for? In this case it's mL/dose. So that's what I write down first. 2) what do I have on hand? Since we know we want ml/dose the 10mL will go on top and the 20meq will go on bottom. 3) What's the order calling for? We know that each unit has to cancel out so 2 meq will go on top and 100mL will go on bottom. Now, we cancel out like terms. 10mL and 100mL cancel out and 20meq and 2meq cancel out. What we need to finish with mL on top... We still have that 500mL left throw it on top. It should look like this:

10 X 2 X 500/ 20 X 100 = 5

Remember first write down what you are solving for and proceed with your "railroad" tracks until you are left with what you are solving for. Good luck with the rest of your clinical calculations and I would be happy to help with anytime.

Guests · Apr 22, 2014

--The doctor orders KCL 2 mEq/100 ml of D5W. On hand is KCL 20 mEq/10 ml and a 500 ml bag of D5W. How many mls of KCL will you give?

If this is the question verbatim, it's a little problematic... and NOT how you would ever see it in practice.

The simple answer to "How many mls of KCL will you give?" doesn't require anything to do with D5W or anything else, right? It's simply asking what volume of the KCl solution holds 2 mEq.

By inspection one can say, "one milliliter," right?

Using proportions:

[TABLE=width: 303]

[TR]

[TD][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center][/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]----[/TD]

[TD=align: center]=[/TD]

[TD=align: center] ----[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]10 mL[/TD]

[TD=align: center][/TD]

[TD=align: center] V[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]x[/TD]

[TD=align: center]----[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]10 mL[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]x[/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center]x[/TD]

[TD=align: center]10 mL[/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]10 mL[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center]x[/TD]

[TD=align: center]----[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[/TR]

[TR]

[TD]V[/TD]

[TD]=[/TD]

[TD]1 mL[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[/TR]

[/TABLE]

However, the doctor ordered "KCL 2 mEq/100 ml of D5W" which is telling you the dilution the doc wants... that is, 1 mL of KCl (which is 2 mEq) into 100 mL of D5W... which means your solution is actually 2 mEq in 101 mL of solution... (1 mL of KCl and 100 mL of D5W)...

If instead somebody wants you to use the entire 500 mL bag of D5W, you'd have to put 1 mL of the KCl stock into the bag so now you'd have 2 mEq of KCl in 501 mL of solution...

In reality, what you'd do (if you didn't have a dilute K-rider stock) is put the entire 10 mL of KCl (that is, 20 mEq) into the 500 mL D5W bag and then give... how many mL?

Keeping in mind that your bag now has 20 mEq of potassium chloride in 510 mL of solution (10 mL of KCl and 500 mL of D5W)...

[TABLE=width: 303]

[TR]

[TD][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq

[/TD]

[TD=align: center][/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]----[/TD]

[TD=align: center]=[/TD]

[TD=align: center]----[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]510 mL[/TD]

[TD=align: center][/TD]

[TD=align: center]V[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]x[/TD]

[TD=align: center]----[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]510 mL[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]x[/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center]x[/TD]

[TD=align: center]510 mL[/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]510 mL[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]=[/TD]

[TD=align: center]2 mEq[/TD]

[TD=align: center]x[/TD]

[TD=align: center]----[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[TD=align: center]20 mEq[/TD]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center][/TD]

[/TR]

[TR]

[TD=align: center]V[/TD]

[TD=align: center]=[/TD]

[TD=align: center]51 mL[/TD]

[TD=align: center][/TD]

[/TR]

[/TABLE]

Now practically speaking:

2 mEq of potassium is just a tiny bit... typical potassium doses are a factor of 10-30 higher than this... (20-60 mEq)
IV potassium is typically given in one of two ways... either from a "K-rider" piggybacked onto maintenance fluids (because the stuff burns like heck otherwise) which K-riders are generally 20 or 40 mEq in 100 mL or... or from a liter bag commonly 20 mEq/100 mL

Anyway, the math is what it is... and is shown in its entirety above...