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Discussion

Math Calculation Help Please!!!!!

I am practicing once again for another math test in Pharmacology. I want to ask for some assistance:wink2: Than you!!!!!!

4. You want to infuse 100 ml of metronidazole over 45 minutes via a left forearm peripheral angiocath #20gauge. At what hourly rate (ml/hr) do you program the pump?

ml/hr = 100 ml/45min x 60min/1hr = 133ml/hr

a. The pump is malfunctioning after 15 minutes and you switch to a gravity set. How much of the volume of metronidazole has infused after 15 minutes (pre malfunctioning!)?:banghead: I got stuck here?????

I wasn't sure ????

b. For the remaining volume, how many drops per minute do you count for the infusion to finish in the recommended infusion time of 30 minutes? Drop factor is 15gtts/ml.

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Well it seems to me that if you have 100ml infusing in 45 minutes, and 15 minutes have passed (1/3 of the infusion time) I just break down the fluid into thirds, which is 33ml. 33ml x 3 = 99ml.

So we have approx 66 more ml's to infuse per gravity. The second part of the problem, I cannot remember the formula to figure out right now.

For the second part, I figured this way-

66ml x 15qtts/ml= 33qtts/min.

30 min

I do believe this works. You want to give 66 ml in 30 minutes, which means giving 2.2 ml/min. 2.2 X 15=33qtts/min.

Granted I have not done drip factors in approx 5 years, and I just worked a rough 12 hour shift, but I believe this is right.

Okay, so I just found my nursing reference. The formula for qtts/min-

Volume (66ml) X gtt factor (15qtt/ml)

Time (in minutes- 30)

It's really easy once you know the formulas.

  • Experts

you want to infuse 100 ml of metronidazole over 45 minutes via a left forearm peripheral angiocath #20gauge. at what hourly rate (ml/hr) do you program the pump?

100 ml/45 minutes
(infusion rate)
x 60 minutes/1 hour
(conversion factor)
= 133.333
, rounded off to
133 ml/hour
rate to program the pump

the pump is malfunctioning after 15 minutes and you switch to a gravity set. how much of the volume of metronidazole has infused after 15 minutes (pre malfunctioning!)?

if you have 133 ml infusing per hour, then how many ml are infusing in 15 minutes? that is your new problem. that is a simple ratio.

133 ml/hour = x ml/15 minutes

1 hour = 60 minutes, so

133 ml/60 minutes = x ml/15 minutes

cross multiply

60x = 1995

x =
33.25 ml
, rounded off to
33 ml
have infused after 15 minutes

for the remaining volume, how many drops per minute do you count for the infusion to finish in the recommended infusion time of 30 minutes? drop factor is 15gtts/ml.

to calculate the remaining volume subtract the volume already infused from the amount you started with.

100 ml
(starting amount of metronidazole)
- 33 ml
(already infused)
=
67 ml
(needs to be infused)

now, calculate the drip rate (gtts/minute) for 67 ml by gravity over 30 minutes with a 15 gtts/ml set:

67 ml/30 minutes
(amount to infuse)
x 15 gtts/1 ml
(drip factor of tubing)
= 33.5 gtts/minute,
rounded off to
34 gtts/minute

  • Author

Thanks Daytonite I usually don't use the ratio method, but the way you have explain it makes a lot of sense to me now for the 1st time.

Thank you:nuke:

  • Author

Thanks cursenurse for your help

email me and I can give you a great packet that really explains medical math for the non-math person. If I knew how to attach it I would, but I am new to the forum.

  • Author

I would appreciate it. Thank you :yelclap:

nyemt195488, thanks for sending that. :)

email me and i can give you a great packet that really explains medical math for the non-math person. if i knew how to attach it i would, but i am new to the forum.

:)

thank you so much for the math packets!!!

you rock!!! :up:

have a great weekend!

jadu1106

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