I need HELP in regards med calcs involving dilutions! PLEASE!

[loveoutloud]

I cannot find the material teaching me how to do this type of questions and the work for the answers is not shown in the answer key. I have not clue how to figure out how many ml of IV solution to dilute the medication in. I will post the question, and I would be more than happy if somebody could just tell me how to do it rather than do it for me!

In how many ml of IV solution will you dilute the medication?

The physician's order reads:

IV NS at 125 ml/hr

Vancomyacin 375 mg IV

THe drug monograph reads:

Final concentrations= 50 mg/ml

Dilute in 100-250ml of IV solution

Administer over at least 60 minutes

The answer key says 125-250 but I do not understand why!!

[morte, LPN, LVN]

something is missing...

[Clovery]

Your drug guide should tell you how to dilute each specific medication. I have Davis Drug Guide and Intravenous Medications (which goes into more detail) by Gahart. For Vancomycin it says "each 500 mg vial must be diluted with 100 mL of NS or D5W and given as an intermittent infusion". It does seem like the question is missing some information, or it's too obvious. The order says NS at 125 ml/hr, and that is your answer. I don't know where the answer key got the 250. The IV med book also says "concentrations greater than 5 mg/mL are not recommended". 375 mg in 125 mL is 3 mg/mL so that is safe. Maybe 250 is the lower limit? (1.5 mg/mL) Although I can't find anything that supports that.

The final concentration that you cited (50 mg/mL) is if you needed to reconstitute a vial of the medication (if it started as a powder or more concentrated liquid). It needs to be diluted further than that for IV administration. You should probably ask your instructor about this question; it seems unclear to me and I'd not know what to do if it showed up on a test.

[Esme12, ASN, BSN, RN]

I agree with morte something is missing.

[nurseprnRN, BSN, RN]

I wrote a really good explanation for this (Well, I thought it was pretty useful),.. and it seems to be gone. Let's try again.

IV NS at 125 ml/hr ((doesn't matter, extraneous information))

Vancomycin 375 mg IV ((total amount of dose--but for most of this problem, that doesn't really matter!))

THe drug monograph reads:

Final concentrations= 50 mg/ml ((if it's more concentrated, it could be harmful))

Dilute in 100-250ml of IV solution ((Aha! Here we go. If it's diluted in this range of volumes, it won't be in the harmful range. Your IV is supposed to go at 125cc/hr, so that's the minimum))

Administer over at least 60 minutes ((So, you have 125 cc with the med in it and you give it over an hour -> 125cc/hr. If you put it in 250cc, then it's 250cc/hr.))

Now, all this considered, here is something else to think about. If you ever get an order, a part of a medical or nursing plan of care, or anything else that appears to have missing information (and this one does, I agree), you, the nurse, must clarify it with the person who wrote it. Don't guess. Get it clarified. In this case, it would be the faculty person who gave you such a goofy question. Go ask that person. Well, don't tell him/her I said it was goofy. But do say that you need clarification because the parameters are not well-described. This is good practice for later when you have to have a physician clarify an order.