General question on infusion calculations

[furelite]

OK, so let's say you reconstituted a drug to equal 7.5 mL to inject in 100 mL of D5W. Why do you base your drop factor on the 100 mL and not 107.5 mL, which is the really the new volume? I swear I have seen it worked both ways, but in my book it is based on 100 mL.

[Double-Helix, BSN, RN]

The math is easier? Technically you should calculate the rate based on the full volume. Sometimes the nurse or the pharmacy will withdraw 7.5mL of the D5W before injecting the medicine, depending on the order, so in that case the total volume is 100mL. If the problem reads "The nurse has reconstituted X drug... which yields 7.5mL in 100mL D5W, the assumption is the total volume is 100mL, not 107.5.

Realistically, as long as you continue the infusion until the patient receives the entire volume in the bag, the exact rate of the pump doesn't really matter.

[furelite]

Ok, thanks. The question actually specifies that the nurse first reconstitutes the drug (previous question was how to reconstitute the drug) and injects it into the existing 100 mL quantity. So to me, that is 107.5. But the book solves it using 100 mL. I appreciate your reply.

[Esme12, ASN, BSN, RN]

follow your book for the sake of calculations...the real world is as Ashley says.....I do however remove volume when it is a titrated drip like Dopamine, Dobutrex etc.