More IV dosage calculation problems: Please Help!

Daytonite, BSN, RN · Jan 19, 2006

Determine the following in drops per minute using the drop factor provided.
1. 3000 ml D5W at 125 mL/hr
10 gtt/mL
125 x 10/60 = 20.83 = 21 gtt/min Is that the correct answer?

Yes, 21 gtts/min is correct! You did this using the short cut. Here is how to set it up by dimensional analysis. . .

125 mL/1 hr.

x

10 gtts/1 mL

x

1 hr/60 min. (

conversion factor from hours to minutes

)

By simplifying and cancelling out labels you get the following:

(125 x 10 gtts x 1)

/

(1 x 1 x 60 min.)

=

1250 gtts/60 min

=

20.8 gtts/min,

or

21 gtts/min

(

rounded off

)

Here is another problem, please tell me if this is correct:
150 mL D5W infusing at 20 macro gtt/min. Drop factor: 15 gtt/mL. Calculate infusion time.
150 x 15/ 20 = 112.5 minutes...Is this correct and do I leave the problem like that?

If I am understanding this problem correctly, it is asking how long it is going to take to give this 150 mL of D5W. Now, where I get confused here is that the drip factor on macro drop tubing is 10 gtts/mL. So, the infusion is going at 120 mL/hour at 20 macro gtts/min. It will take 75 minutes, or 1 hour and 15 minutes, to infuse the entire 150 mL. Now, changing to 15gtt/min tubing (if I am understanding this correctly) is not going to change the infusion time UNLESS you want to give 150 mL at 20 gtts/min with 15gtt/min tubing. Then, it will take you the 112.5 minutes. The math to do this is:

150 mL/

x

min.

x

15 gtts/1 mL

=

20 gtts/1 min

Simplfying and cancelling labels you get the follow ratio:

1150 gtts/

x

min

=

20 gtts/ 1 min.

Cross-multiply to get this equation:

20x

=

2250

-->

x

= 112.50 min.

, or

1.875 hours