Med Calc..Show me set up...Please!!

[Spikey74]

#1

Zofran 0.15 mg/kg IVPB 30 minutes before chemotherapy. The label on the vial states to dilute the drug in 50 ml of D5W and infuse over 15 minutes. Calculate the flow rate for a patient who weighs 55 kg, when the drop factor is 10 gtts/ml.

#2 Hycantin 3.25 mg IV daily for 5 days. Repeat every 21 days. The label on the vial reads

4 mg/4 ml. Directions state to withdraw the dose and add to the 50 mls of D5W and infuse over 30 minutes. Calculate the flow rate in ml/hr.

[shaas, ASN, RN]

#1. What are your flow rate units? Here are all three scenarios:

gtt/mL = (50 mL/15 min) (10 gtt/mL) = 33 gtt/min

mL/min = (50 mL/15 min) = 3.3 mL/min

mL/h = (50 mL/15 min) x (60 min/1 h) = 200 mL/h

#2. mL/h = (50 mL/30 min) x (60 min/1 h) = 100 mL/h

*Notes:

1) Don't be bogged down by extraneous information. The amount of medication that pt. needs is not relevant to rate calculation because it's gonna be dumped into that IV bag.

2) When minute amount (mg) of meds are added to the IV bag, the volume change is negligible. So, assume the total volume to be 50 mL in both cases, even after the meds have been added.

[Spikey74]

Thanks Shaas...I was reading too much in question #1 but for question #2 I did it the way you have it set up and got the answer marked wrong...106.5 ml/hr was suppose to be the answer. IDK maybe the answer key is wrong but thanks for your help these questions are worded tricky!

[Esme12, ASN, BSN, RN]

This is an excellent web site!

DosageHelp.com - Helping Nursing Students Learn Dosage Calculations

[shaas, ASN, RN]

Spikey, thank you for the information regarding #2; apparently, in this question the added medication volume matters.

So, a change of m.o. and here is a new set-up:

1. 3.25 mg x (4 mL/4 mg) = volume of med. needed = 3.25 mL

2. 50 mL (D5W) + 3.25 mL (med) = 53.25 mL *Notice the total volume exceeds 50 mL.

3. (53.25 mL/30 min) x (60 min/1 h) = 106.5 mL/h

Scientifically and technically speaking, all initial volume increases when a substance is added, and the final volume is greater than the initial volume. However, in nursing, we must discern which case falls into which category.

Here is my suggestion. Next time, when med concentration is given (mg/mL) follow the method above. Find out in mL how much med will be added to the IV fluid. For #1 question types, there was no way for us to figure how much volume would be added to the IV fluid. The question formulator implicitly assumed that it would be negligible, so, the conc. was omitted and not given to us.

Good luck!

Shaas