IV Calculations

tookewlandy · Dec 30, 2006

it seems maybe its a 2 step problem

First find out how long it would take 1000 mL to infuse at 50mL/hr... i got 20 hours

Next 60gtt/1mL x 1000mL/1200min(20 hours in minutes) = 50 gtt/min

Now i think that is what it is, i gotta go back and review Iv calculations myself

mkmm429 · Dec 30, 2006

Am I dividing the volume the 1,000 into the 50/ml to get the first answer?

Jules A, MSN · Dec 30, 2006

:uhoh21: Hello, I am a current nursing student and I am having a problem with a specific calculation question: there are 2 different types of calculations, the first 1 is:
A unit of packed cells (250ml) to infuse in 4 hour. Drop Factor 20gtt/ml.
These I can get, the answer I got was 20.8-21/gtt/min.
This one is difficult for me due to the fact I can not figure the equation:
1 Liter (1,000ml) of D5 o.45% NS at 50ml/hr, Drop Factor 60gtt/ml. UGH!
Can someone help me with the steps on how to figure this out and if possible give me the answer so I can refer to it! Thanks for all your help, I love this webpage! It has been extremely helpful!!!

I did them exactly the same way. You really don't need to divide the 1,000mls into 50ml/hr unless the problem asks for the total running time. Since you know that it is 50 mls each hour if you divide the 50mls by 60 seconds to the amount you will need per minute 0.833mls per minute multiplied by 60gtt/ml and you get 49.999 or 50 gtts per minute. Hope thats right.

P.S. The first time I got a problem like this the 0.45% NS freaked me out but I learned to just ignore those numbers. Good luck.

mkmm429 · Dec 30, 2006

Thanks, I have become very good at ignoring the other numbers, they try to trick you on these types of questions, I am finding that in my Foundations of Nursing course also. Having kids, I think ignoring things comes like breathing to me! thanks for your help I will try to work these out! :nurse:

VickyRN, MSN, DNP, RN · Dec 30, 2006

The way this second problem is presented, isn't too clear. Exactly WHAT do you need to know for this problem? Do you need to need how many hours it is to run for the entire infusion and then gtt/ minute or just gtt/ minute?

In order to figure gtt/ minute on the 2nd problem, all you need is the gtt/ml and ml/hr. The other information (1000 ml of D5 .045% NS) is superfluous, meant to throw you off. You have to learn to sort out the unnecessary information from the absolutely critical information. Afterall, this is the way it is in "real life." Always ask yourself - WHAT is the problem asking? WHAT parameters do I need to work out this problem? Then throw out the rest.

To figure gtt/ minute, start with dose desired (gtt):

60 gtt X 50 ml X 1 hr = 50 gtt

ml 1 hr 60 min min

(Or 60 gtt/ml X 50 ml/1 hr X 1 hr/60 minutes = 50 gtt/ minute)

However, if you also need to know HOW MANY HOURS of infusion (1000 ml D5 0.45% NS @ 50 ml/ hr), again you need to know what information you need and which is unnecessary. You don't need to know the D5 0.45% NS. All you need to know is 1000 ml and 50 ml/hr.

To figure hours of infusion, start with dose desired (hr):

1 hr X 1000 ml = 20 hours of infusion

50 ml infusion

(Or, 1 hr/50 ml X 1000 ml/ infusion = 20 hours of infusion)

Hope this helps :)

Daytonite, BSN, RN · Dec 31, 2006

here is how both problems are worked using dimensional analysis:

a unit of packed cells (250ml) to infuse in 4 hour. drop factor 20gtt/ml

since you want the final answer to be a fraction (or ratio) with the labels gtts/min, you set the problem up so the terms of the equation are fractions that are multiplied together. you are manipulating these terms so that the unwanted labels on the numbers (ml and hours) are going to get canceled out leaving you with final labels of gtts/min. it is difficult to write fractions out with the numerator over the denominator on this website, so it might help if you take this problem solution i'm giving you and re-write it on a piece of paper with numerators over denominators along with the labels that go with each number, so you can see how the labels in the numerator of one fraction are canceling out the labels on denominators in another fraction, etc. the terms of the equation are going to be the dose you want to give as well as the drip factor of the tubing you are using and any conversion factors you need. so,

250 ml

/

4 hours

(dose desired)

x

20 gtts

/

1 ml

(drop factor of iv tubing you are using)

x

1 hour

/

60 min

(conversion factor)

=

20.8333 gtts/min

(after performing the math and canceling out labels)

=

21 gtts/min

(rounded off)

1 liter (1,000ml) of d5 0.45% ns at 50ml/hr. drop factor 60gtt/ml.

you want the final answer to be a fraction (or ratio) with the labels gtts/min.

50 ml

/

1 hour

(dose desired)

x

60 gtts

/

1 ml

(drop factor of iv tubing you are using)

x

1 hour

/

60 min

(conversion factor)

=

50 gtts/min

(after performing the math and canceling out labels)

mkmm429 · Jan 1, 2007

Thanks for all your responses, I guess I better start practicing, as you can see math is not one of my strong points and I really need to get it straight. Thanks!

Cosper123 · Nov 23, 2007

This one is difficult for me due to the fact I can not figure the equation:
1 Liter (1,000ml) of D5 o.45% NS at 50ml/hr, Drop Factor 60gtt/ml. UGH!

Ok here is how I set up all my IV calculations - O/T X D /60

Where O=order, T=time in hours, D=drop factor, and the 60 is for gtt/ml(breaking it down to seconds)

The section O/T gives you ml/hr....

Knowing this, it makes it apparent that the 1,000ml is not needed when you notice 50ml/hr.

So you are left with 50(hourly rate) x 60 (drop factor) /60(breaking it down to seconds)

Which gives you 50 gtts

Hopefully this is easier to understand for anyone stumbling across this thread than the other posts here trying to explain, because that was my intent! Hope it helps!