2nd year dosage calc/ IV

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Hi. Just starting 2nd year in ADN program and they have given us some math problems over break that I am unsure of how to do. Help if ya can!

Order: Heparin drip 25,000 U heparin in 250 mL 0.45% NS to infuse at 1200 U/hr.

Drop factor: On infusion controller

Flow rate = ? mL/h

I don't know if they are just throwing in a bunch of info you don't really need or what but I just took 250mL and divided it by 1 hour. Am I way off?

Order: Penicillin G 1,000,000 units in 100 mL NS to run over 30 minutes q4h.

Drop factor 10gtt/mL

Flow rate: ? gtt/min

Again, I don't know if they are throwing in a bunch of info that's not used to calculate or what but I am kinda lost.

Thanks!

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order: heparin drip 25,000 u heparin in 250 ml 0.45% ns to infuse at 1200 u/hr.

drop factor: on infusion controller

flow rate = ? ml/h

you are not being asked to calculate the infusion rate to run the entire bag of heparin over 1 hour, you are being asked to calculate the infusion rate to run the heparin at 1200 units/hour.

the first step in solving this problem is to determine the concentration per ml. although this information should be contained on the package or container, you should know how to determine this yourself. this is easily accomplished by dividing the total amount of heparin by the total volume (25,000 units/250 ml = 100 units/ml).

the hourly dose, 1200 units, was provided for you. so, to determine infusion rate all you need to do is divide the dose by the concentration ([1200 units/hour]/[100 units/ml] = 12 ml/hour).

order: penicillin g 1,000,000 units in 100 ml ns to run over 30 minutes q4h.

drop factor 10gtt/ml

flow rate: ? gtt/min

once you have determined that you have the correct medication and concentration, all they are asking for here is a simple rate calculation. the formula for doing this is: volume x gtt factor/time. so, for this calculation you set the problem up as follows: 100 x 10/30 or 1000/30=33.33. since you are delivering this via a standard administration set you would need to round to the nearest whole number, in this case 33.

hope this information was helpful. :specs:

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Specializes in VA-BC, CRNI.

Beat me to it.

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Thank you very much, I understand. Another one is:

Order: Ancef 1 g in 50 mL D5w to run over 30 min q6h

Drop factor: On infusion pump

Flow rate ? mL/hr

Not sure if I take the 50 mL and divide by 30 minutes or 360 minutes.

Thanks Again!

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Specializes in being a Credible Source.
Thank you very much, I understand. Another one is:

Order: Ancef 1 g in 50 mL D5w to run over 30 min q6h

Drop factor: On infusion pump

Flow rate ? mL/hr

Not sure if I take the 50 mL and divide by 30 minutes or 360 minutes.

Thanks Again!

Why would you divide by 360 minutes? The problem statement tells you that it's running over 30 minutes.

Also, since you're looking for the flow rate per hour (mL/hr), you need to convert 30 minutes to hours. How many hours are in 30 minutes?

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I got the 360 minutes by taking 6 hours x 60 minutes. Okay so I need to focus on the ml/hr and not the minutes because the problem is asking for ml/hr. I think what is confusing me is the 30 minutes and 6 hours. There is 0.5 hours in 30 minutes.

Thanks

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Okay I have been looking at this tooooo long. I get it. Sorry to make myself look dumb. I hate math and always make it harder than it is. The answer is 100mL/hr. Duh.

Thanks!

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Specializes in being a Credible Source.
Okay I have been looking at this tooooo long. I get it. Sorry to make myself look dumb. I hate math and always make it harder than it is. The answer is 100mL/hr. Duh.

Thanks!

Yep, you've got it.

The "q6h" really has nothing to do with the problem.

Try to think about what's really happening before you start trying to throw equations down on paper.

In this case, you've got a bag of fluid that's supposed to flow into a patient. You know how much (strictly speaking, what volume...) stuff you've got to infuse and you know the time in which it must be done so you just need to figure out how fast it needs to go.

It's no different than saying "you need to drive 45 miles in 1/2 hour - how fast must you drive?" (the answer is 90 miles per hour, right?) or "How many minutes will it take you to drive 45 miles if you're traveling at 90 mph?" (1/2 hr or 30 min).

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Specializes in being a Credible Source.

Also, apply the "does this make sense?" test...

If you infuse 50 mL over 360 minutes, that would be a rate of 0.14 mL/min or 8.3 mL/hr... that is very slow.

When you saw the "q6h", did you understand that it meant "every 6 hours?" If not, then be sure that you understand all the shorthand notation used in these kinds of problems.

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the easiest way to do these types of problem is: volume x drip factor/time (always in minutes). so for this problem:

order: penicillin g 1,000,000 units in 100 ml ns to run over 30 minutes q4h.

originally posted by skyflier viewpost.gif

drop factor 10gtt/ml

flow rate: ? gtt/min

your volume is: 100ml

your drip factor is: 10 gtts/min

your time is: 30 min

so the equation would be 100ml x 10 gtts/min divided by 30 min = 33.3 gtts/min

that always seems to be the easiest for me. i hope this helps also.

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