Question

A TPN order calls for the amounts on the left to be made from the items on the right. The total volume is to be 250 mL. How much of each ingredient do you need to prepare this TPN?

Order What you have
Aminosyn 2.5% Aminosyn 8.5% 500 mL
Dextrose 7.5% Dextrose 50% 1000 mL
KCl 4 mEq KCl 2mEq/mL 10 ml
Ca Gluconate 2 mEq Ca Gluconate 4.4mEq/ml 25 mL
Ped MVI 5 mL Ped MVI 10 mL


What I really need is an explanation of the method because I'm having trouble determining the values.

Answer 1

you're basically doing dilutions. Use this: \[C _{1}V _{1}=C _{2}V _{2} \]

Answer 2

you're gonna add each one of the solutions then top it up to 250 mL with water (distilled)

Answer 3

I have been using that equation but I'm not sure how it comes to the answers. For example, the answer for the amount of Aminosyn needed to produce a 2.5% product is 73.5 mL, but I'm doing the equation the same way and it amounts to 147, double the answer. I don't understand where the extra division comes in.

Answer 4

For: Aminosyn 2.5%

0.025(250mL) =0.085(V) -> V=73.529 mL

Answer 5

you're probably doing it backwards

Answer 6

That makes sense but where did the 250mL come from?

Answer 7

the total volume of the solution you're making is 250 mL

Answer 8

So the 500 mL from the 8.5% Aminosyn is irrelevant to the equation?

Answer 9

well thats how much you have, but yeah, you don't use it in the calculations

Answer 10

you're figuring out how much solute you need

Answer 11

thanks a lot! it was stressing me out.