# IV Calculations (Help!)

1. Hey nurses!

I've been trying to solve these problems however I can't find the solution. Any instructions on how to do these would be so grateful! Thank you!

1) Cephalexin 400mg in 100ml of fluid to run over 20mn. Drop Factor is 15.
At what rate would you set the infusion pump?

2) You are to give 600units of heparin per hour.
Each liter of solution contains 25,000 units.
You will set the pulp at _____ ml/hr.
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Joined: Feb '13; Posts: 6

3. Question 1 is trying to trick you. You don't need to know the mg of medication or the drop factor. All you need to know is that you need to give 100mL of medication in 20mins. How fast do you need to run the medication?

Dose (100mL) / Duration (1/3 hr) = ?

I have no idea how the answer you supplied for question 2 is correct. Is that all the information that was given? If you have 25,000 units in 1 liter (1000 mL) then there are 5,000 units in 1/5 (200 mL) of the bag. Much more than the ordered 600 units. In order to solve this problem:

Desired dose (600 units) / available dose (25,000 units) x volume available (1000mL) = ?
4. Quote from jenxsmiles
Hey nurses!
I've been trying to solve these problems however I can't find the solution. Any instructions on how to do these would be so grateful! Thank you!

1) Cephalexin 400mg in 100ml of fluid to run over 20mn. Drop Factor is 15.
At what rate would you set the infusion pump?
The question asks for mL/hr not gtts/min so the drop factor is irrelevant. The medication dose is also irrelevant to the math here. You need to infuse 100 mL in 20 min... so how many mL would you infuse in an hour?

Quote from jenxsmiles
2) You are to give 600units of heparin per hour.
Each liter of solution contains 25,000 units.
You will set the pulp at _____ ml/hr.
If you have 25,000 units of heparin in one liter and you infuse 200 mL in one hour, the patient will have receive 5,000 units of heparin, no?

So, 25,000 u/1,000 mL= 25 u/mL. If you want to give 600 units, how many mL is that? It is most definitely not 200 mL.
5. Welcome to AN! The larget online nursing community!

We are happy to help with homework but we will not do it for you. Show me what you have so far so I can try to figure how to best help you.

You will be doing calculations for the rest of your career so you need to get good at them.

You will find this site estremely helpful....DosageHelp.com - Helping Nursing Students Learn Dosage Calculations
6. If 100cc runs in over 20 minutes, how many cc would run in over 60 minutes? You can do that in your head. It may help to draw a picture on a piece of paper to help you visualize it, but that's really all there is to that one.

The other one might benefit from a picture too. If there are 25,000 units in the liter, but you only want 600 units at a time, how much of the liter is that? You know it's a pretty small number, because 600 is such a small part of 25,000, right?
7. Thank you for all the help, I've figure it out.

1) Cephalexin 400mg in 100ml of fluid to run over 20mn. Drop Factor is 15. At what rate would you set the infusion pump? Answer: 300ml/hr (Can't figure how to get this answer)

It's asking for ml/hr so what I did is take the 400mg/20min = 20

Then...
Take the 20 x15 gtt = 300 ml/hr
***But I still don't know why I used the 400mg rather than the 100ml to get the answer??

2) You are to give 600units of heparin per hour. Each liter of solution contains 25,000 units. You will set the pulp at _____ ml/hr. Answer: 200mL (Can't figure how to get this answer)

25,000 600
-------- = ------
1000ml (1L) X

Just cross multiply..
25,000 X = 600,000

Total - 24ml/hr NOT 200.
8. Quote from Esme12
Welcome to AN! The larget online nursing community!

We are happy to help with homework but we will not do it for you. Show me what you have so far so I can try to figure how to best help you.

You will be doing calculations for the rest of your career so you need to get good at them.

You will find this site estremely helpful....DosageHelp.com - Helping Nursing Students Learn Dosage Calculations
I've done the 1st one but instead I've used the 400mg rather than the 100ml and got the correct answer. However, I did do the 100ml/20min and got 5.

5 x 15gtt = 75 (wrong answer)

My question is.. Why did I have to use the 400mg rather than the 100ml?
9. Quote from jenxsmiles
I've done the 1st one but instead I've used the 400mg rather than the 100ml and got the correct answer. However, I did do the 100ml/20min and got 5.

5 x 15gtt = 75 (wrong answer)

My question is.. Why did I have to use the 400mg rather than the 100ml?
You don't. You're working this wrong. This is what you did:

400 mg/20 min = 20 mg/min. When you multiply this by 15 gtts/mL, it does NOT give you the answer in mL/hr. It would give you 300 gtts*mg/min*mL. NOWHERE near what you're looking for. Pay attention to the units you're using.

In order to figure out mL per hour, you need to take your volume which is 100 mL. It is set to infuse over 20 min. How many "20 min" are in one hour? Three, right? So all you need to do is simple multiplication to figure out your rate in mL per hour.