How to calculate for "how much remains after X-Hours?"

Editorial Team / Admin · Feb 6, 2015

You should have the information needed to calculate how much would infuse from 12:00 to 2:00. The volume remaining is what didn't infuse- so if you start with a 500mL bag and infuse 250mL, how much is left? That's how you should think about these questions.

Bedside_Life RN · Feb 6, 2015

Lets say that you are infusing Magnesium IVPB 50 mL, over two hours, using secondary tubing with a drop factor of 15. The infusion is ordered to be started at 1300.

What is the rate in mL/hr?

What is the VTBI?

What is the volume that will be infused in 30 minutes?

What volume will be left at 1400?

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ChooSoul · Feb 6, 2015

Lets say that you are infusing Magnesium IVPB 50 mL, over two hours, using secondary tubing with a drop factor of 15. The infusion is ordered to be started at 1300.
What is the rate in mL/hr?
What is the VTBI?
What is the volume that will be infused in 30 minutes?
What volume will be left at 1400?
**Tell how you would start this problem, and we'll help from there**
**Even if you get stuck, at least try it. You are learning***

Im lost. you didnt give the rate.

heres an example of what im talking about.

Client is recieving 40gtt/H dextrose, IV set works as 10gtt/ml, the beginning volume of dextrose is 1000ml at 12 noon. How many ml will remain at 3pm?

psu_213, BSN, RN · Feb 6, 2015

Client is recieving 40gtt/H dextrose, IV set works as 10gtt/ml, the beginning volume of dextrose is 1000ml at 12 noon. How many ml will remain at 3pm?

Although I have never seen an order written in gtt/hourâ€¦.

1. If the pt. gets 40 gtts. in one hour, and each 10 gtt deliver one mL, how many milliliters is the pt. getting per hour?

2. Then how much would the pt. get in the 3 hour window?

3. If you started with 1000 mL of the dextrose, how much is now left?

ChooSoul · Feb 6, 2015

Although I have never seen an order written in gtt/hourâ€¦.
1. If the pt. gets 40 gtts. in one hour, and each 10 gtt deliver one mL, how many milliliters is the pt. getting per hour?
2. Then how much would the pt. get in the 3 hour window?
3. If you started with 1000 mL of the dextrose, how much is now left?

Oh shoot!

Sorry! its actually 40gtt/min! haha! thanks for mentioning it

psu_213, BSN, RN · Feb 6, 2015

Oh shoot!
Sorry! its actually 40gtt/min! haha! thanks for mentioning it

Then for #1: they get 40 gtts in one minute. How many mL do they get in that minute if they get a mL for every 10 gtts? How much would they get in an hour? (Parts 2 and 3 stay the same.)

mrsboots87 · Feb 6, 2015

Drop factor of 15 = 15gtt/min. She did give the rate.

Bedside_Life RN · Feb 7, 2015

drop factor of 15 would reflect 15 drops (gtt) per mL. So if you are infusing 50mL, you would be infusing 750 drops Total. If 750 drops are to be infused over 2 hours, there would be 375 drops q1h...... you can further break it down by smaller time intervals in this same way. So the rate is up to you to figure out....?

To do this, take the 375 gtt (or 25mL) per hour and divide by 60 minutes. So the drops per minute would be 6.25 and the mL per minute would be 0.42mL.

this would answer gtt/min and mL/min.

if you work it out for both gtt and mL it will give you additional resources to work the problem out.

KelRN215, BSN, RN · Feb 9, 2015

The formula you are looking for is subtraction. You figure out how much has infused and then subtract that volume from the total volume and you get the remaining volume.

Ex, if you have 1,000 mL D5NS infusing at 100 mL/hr and you hang the bag at 12:00, at 2:00 there will be 800 mL remaining in the bag. 12:00-2:00 is 2 hours, you are running 100 mL/hr x 2 hrs = 200 mL. 1000 mL total -200 mL infused = 800 mL remaining. Don't make this more complicated than it needs to be.

mrsboots87 · Feb 15, 2015

Ey yi yi. I just came back to this and saw my error. So as not to look like an idiot, I just want to note I totally meant that drop factor of 15 means 15gtt/mL not min. Oops.

nurseprnRN, BSN, RN · Feb 16, 2015

Im lost. you didnt give the rate.
heres an example of what im talking about.
Client is recieving 40gtt/H dextrose, IV set works as 10gtt/ml, the beginning volume of dextrose is 1000ml at 12 noon. How many ml will remain at 3pm?

She did give the rate. It says, "50ml over two hours." If you can't do that in your head and come up with "25cc/hour" I don't think we can help you.

I think some of your problem is that you aren't familiar enough with the components of these word problems, so you get flustered if you don't see them in a particular order or format.

In your example above, there is no such prescription as gtt/hour. That's one of your problems right there. Reread it and try again.