# help me calculate this problem.. - page 2

by EmilyEmily

1,437 Views | 18 Comments

1. An infusion ordered of 2g in 500 mL is ordered at 60mL/hr 2g/500mL ???... Read More

- 0Jan 28, '13 by KelRN215Quote from EmilyEmilySo you have the same concentration as before. Your book doesn't "show" you how to do this because the authors assume you know how many minutes are in an hour.I'm having trouble finding the flow rate with this problem

A 3mg/min dosage is ordered. The solution strength is 2g in 500 mL. What is the mL/hr flow rate?

**2g/500mL...**

I dont know what the mL/hr flow rate formula is..my book does not show me how to do this type of problem

You are infusing 3 mg in one minute... so how many mg are you infusing in an hour? You know your concentration so all you have to do is plug in the numbers to convert to mL/hr. - 0Jan 29, '13 by
*akulahawkRN*Quote from EmilyEmilyWrong formula.2000mg/500mL x 3mg/60min

i get the wrong answer with this formula

2000mg/500mL = 4mg/ml. Your ordered dose is 3mg/min. How many mL/min is that? Take that answer and multiply by 60 and you'll have your flow rate per hour.

Perhaps set the problem up as a proportion problem to find the rate per min.

4mg 3mg

---- = -----

1mL X

Solve that... and you'll be 1/2 way to your answer, depending upon what flow rate (ml/min or ml/hr) is being asked. - 0Jan 29, '13 by KelRN215Quote from EmilyEmilyWell look at the way you have this problem set up. Your answer is going to give you mg SQUARED over min x mL. That's no good. You're looking for mL/hr.2000mg/500mL x 3mg/60min

i get the wrong answer with this formula

Your infusion rate is 3 mg/min not 3 mg/hr so you can't use 3 mg/60 min. To change the mg/min rate to mg/hr you multiply by 60 min/hr.

So 3 mg/min x 60 min/hr and the minutes cancel each other out to give you mg/hr.

Then you take your concentration, which you have already figured out and multiply it by that to give you mL/hr. - 3Jan 29, '13 by
*GrnTea*This student is why I hate teaching formulas to new students. They always take all those numbers and jam them in there and come out with something weird like mg^2 (mg-squared), which is meaningless but they don't get that.

Break it down into its component parts, solve them one at a time, and see what it is you're looking at, don't do it all at once. - 2Jan 29, '13 by ♪♫ in my ♥Emily, I've been watching this thread but haven't had time to write out a detailed response.

I will share this, however: Don't try memorizing "formulas," try to understand the basic concept of what you're doing. If you learn the idea, there really are no "formulas," but just simple equations that follow from the information given.

Try to wrap your brain around the following concepts:

1) mass

2) concentration/dilution

3) volume

4) volumetric flow rate

5) mass flow rate

6) fundamental units and derived units

7) density

If I had to guess, you don't really understand one or more of these basic concepts which is why you're getting so confused.

If I were your tutor, we'd be certain that you could clearly articulate just what each of these mean and how they relate to each other. From there, the questions that you're trying to solve are quite simple.

I HIGHLY suggest you spend some time with a good tutor ASAP.loriangel14 and GrnTea like this. - 0Jan 29, '13 by Bandorder is 3 mg (concentration)/ min (time)

available is 2,000 mg(concentration) inside 500 mL(volume)

cross multiply, answer will be = mL / min

2,000 mg is to 3 mg

as 500 ml is to X min.

500mL x 3 mg = 2,000 mg X

= 0.75mL / min... x 60 min (to make 1 hour) = 45 ml/hr

Go to the college library and check out Calculating with Confidence, or any Dosage Calc book, go through every chapter and they should give you both methods of solving the problem the way you like it - 0Jan 30, '13 by LanesmamaI know someone said don't memorize formulas but I do like a formula for this:

want

_____ x vol

have

want 3 mg/min

__________ so first this I do here is make sure my units of mass are the same. 2 g=2000 mg so it now reads

have 2 g

want 3 mg/min

__________ x 500= 3mg/min divided by 2000= 0.0015mg/min X vol (500)

have 2000 mg

0.015mg/min x 500mL= 0.75 mL/min

You need in hours so multiply by 60 (minutes in an hr)= 0.75x60= 45 mL/min