Dosage Help

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Having a hard time with this question. A liter of D5/NS with 10 units of Regular insulin is started at 9:55 AM at a rate of 22 gtt/min. If the drop factor is 20gtt/mL, when will the infusion finish?

Thank you!

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Specializes in Informatics / Trauma / Hospice / Immunology.

First of all the D5/NS and insulin information is irrelevant to the problem, so ignore it.

The I like to start with my volume to be infused on the left of the equation and line up my dimensional analysis (ratios) so that the units each cancel to get me where I need to go... time in this case:

1L (1000ml / 1L) (20gtt / 1ml) (1 min / 22 gtt) = ?

Since the drip rate is just a ratio I flipped it here so that my units all cancel except minutes.

This gives me 909 minutes which seems insanely long right? So I review the equation and see that the drip rate is basically 1 ml per minute so yeah, it will take almost 1000 minutes (minimum drip rate to keep the vein open is 15-30 ml/hr so this is not too insane).

Lastly, convert minutes to hours and minutes and add to 9:55am:

909 minutes ( 1 hr / 60 mins ) = 15.15 hours. 0.15 hours ( 60 mins / 1 hr) = 9 mins.

We have 15 hrs and 9 mins. Adding the 9 mins first gives 10:04am. Then adding 15 hours gives us 1:04am the next day.

Hope that helps! :)

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As noted above, all they want to know is, "How long will it take to use up a liter of fluid at 22gtt/minute using a 20gtt/cc IV set?"

20gtts = 1cc

20,000 gtts = 1000cc

Divide 20,000gtts by 22gtts/minute will tell you how many minutes it will take to run it all out. :)

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