How do I recalculate flow rates for infusions?

0 1. An IV of 500mL was ordered to infuse in 3 hr using a 15gtt/mL set. With 1 1/2 remaining, you discover that only 150 mL is left in the bag. At what rate will you need to reset the flow?
2. An IV of 1000mL was ordered to infuse in 8 hr. With 3 hr of infusion time left, you discover that 600 mL have infused. The set delivers 20gtt/mL. Recalculate the drip rate, and indicate how many drops you will count in the 15 sec to set the new rate. 

0Jan 21, '13 by akulahawkRN, ASN, RN, EMTP ProQuote from EmilyEmilyYou recalculate just as you would for an initial rate... only you plug in the amount you have left in the bag and how much time you have left. For question #2, you do the same and add in the number of gtts you will need to have per minute to ensure the rate is correct.1. An IV of 500mL was ordered to infuse in 3 hr using a 15gtt/mL set. With 1 1/2 remaining, you discover that only 150 mL is left in the bag. At what rate will you need to reset the flow? So you have 150 mL in the bag with 90 minutes to go, correct?
2. An IV of 1000mL was ordered to infuse in 8 hr. With 3 hr of infusion time left, you discover that 600 mL have infused. The set delivers 20gtt/mL. Recalculate the drip rate, and indicate how many drops you will count in the 15 sec to set the new rate. So you have 600 mL to be delivered over the next 3 hours...
You're just overthinking this. 
0Jan 21, '13 by EmilyEmilyQuote from akulahawkCould you work it out?? I keep doing the steps over and over and getting the wrong answerYou recalculate just as you would for an initial rate... only you plug in the amount you have left in the bag and how much time you have left. For question #2, you do the same and add in the number of gtts you will need to have per minute to ensure the rate is correct.
You're just overthinking this. 
1Jan 22, '13 by Mina E.Quote from EmilyEmily1. An IV of 500mL was ordered to infuse in 3 hr using a 15gtt/mL set. With 1 1/2 remaining, you discover that only 150 mL is left in the bag. At what rate will you need to reset the flow?
So you have 150ml to infuse over 90mins at a rate of 15gtt/ml
(150ml/90mins)(15gtts/ml)= 25gtts/min
Quote from EmilyEmilySo you have 400ml of the 1000ml left to infuse at a rate of 20gtt/ml2. An IV of 1000mL was ordered to infuse in 8 hr. With 3 hr of infusion time left, you discover that 600 mL have infused. The set delivers 20gtt/mL. Recalculate the drip rate, and indicate how many drops you will count in the 15 sec to set the new rate.
(400ml/3hr)(1hr/60min)(20gtts/ml)= 44.4gtts/ml or about 44gtts/ml
Over 15secs, you would count 11gttsEmilyEmily likes this. 
0Jan 22, '13 by EmilyEmilyQuote from Mina E.So you have 150ml to infuse over 90mins at a rate of 15gtt/ml
(150ml/90mins)(15gtts/ml)= 25gtts/min
Wait I still don't see how you got 25 for this one..I'm getting 9 
1Jan 22, '13 by akulahawkRN, ASN, RN, EMTP ProSimple math. Do the stuff in parenthesis first, left to right...
150mL/90 min = 1.67 mL/min. Then multiply by the gtt factor.
1.67 mL/min * 15gtts/mL = 25 gtts/min.
As to why we weren't helping that much is that we generally prefer to point the way to the solution and if you follow the pointing, you'll arrive at the solution yourself and understand the result much more concretely than if we spoon feed you the answer.mariebailey likes this. 
0Jan 22, '13 by EmilyEmilyQuote from akulahawkThat method does not work for everyone. I like for someone to work the problem out so that I can see all of the steps and how it was solved. Maybe there was a step that I missed. This forum was made to assist students so I expect people to want to actually helpSimple math. Do the stuff in parenthesis first, left to right...
150mL/90 min = 1.67 mL/min. Then multiply by the gtt factor.
1.67 mL/min * 15gtts/mL = 25 gtts/min.
As to why we weren't helping that much is that we generally prefer to point the way to the solution and if you follow the pointing, you'll arrive at the solution yourself and understand the result much more concretely than if we spoon feed you the answer.