Figuring out IV drip rates

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Specializes in Emergency Dept, M/S.

We have a section on this coming up on our next exam, so I'm studying like a madwoman. Anyway, I wondered if anyone could help with the below problem. I can't figure it out for the life of me:

Your patient is receiving a unit of blood. The pump is set at 125 and there is 450 ml left to infuse. How long will it take to infuse?

I get the answer based on 450ml / 125ml = 3.6 hours, but the answer says 3 hours, 36 minutes. Can someone explain how the .6 equals 36 minutes, because I DON'T get it. Unless there is more to the problem than just division, which very well could be.

As a side note, what formula is everyone using for calculating IV flow rates? I know I used a different formula for med dosage calculation than my instructors did, so I could NOT watch when they taught stuff like that in class, or it screwed up my way of doing it (Dimensional Analysis method). I hate that there are so many ways of doing it. One poor woman in our class was in TEARS because she was getting so confused with it. But of course, it is so, so important to know at least ONE of the methods cold.

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Specializes in Med-Surg, Psych.

Whitney,

I wish I had the answer for you. I am drawing a complete blank and know it's something so simple.

I'll be hoping someone comes along soon to answer.

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Pretty simple. To get the 36 minutes into decimel form just divide the 36 by 60. The 60 being the number of min. in a hour. That gets you the .6 Hope this helps. Which we are always told to round up or down accordingly.

Cheryl

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Specializes in ICU.

I am glad someone else answered this for you although I was going to say .6 of an hour is 36 minutes but with my math ability...... let us just say that when they were handing out the maths abilities I was in the line marked "shopping enjoyment".........going for seconds.

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Specializes in Emergency, Trauma.

3.6 is the same as saying 3 and 6/10ths of an hour. Divide an hour into tenths (60 minutes divided by 10) and you get six. So, if one tenth of an hour is six, then six tenths of an hour (6 x 6) is 36, i.e. thirty six minutes.

Calculating IV flow rates using MAGIC NUMBER method-

Determining which "magic number" you will use depends on your tubing gtt size.

(60 divided by gtt size equals magic number)

For example,

60 gtt tubing; 60 divided by 60 equals ONE.

15 gtt tubing; 60 divided by 15, equals FOUR.

10 gtt tubing; 60 divided by 10 equals SIX.

Okay, so once you know which "magic number" you're using, you then divide your ordered rate (ml/hr) by the magic number to get your gtts/min.

For example,

You have an order for NS at 120cc/hr using 15 gtt tubing. What is your drip rate in gtts/min?

60 divided by 15 equals FOUR (magic number)

120 cc/hr divided by 4 equals 30 gtts/min.

Another example,

Your order is to infuse D5NS at 240ml/hr using 10 gtt tubing. What is your drip rate in gtts/min?

60 divided by 10 equals SIX (magic number)

240ml/hr divided by 6 equals 40 gtts/min

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Specializes in critical care; community health; psych.

I use dimensional analysis. Setting up the problem is the same every time. Once you know the formula, it works for everything.

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Specializes in Emergency Dept, M/S.

Thank you!!! You've made me a happy studier! LOL

I was just using the magic number method last night also. It does seem a lot easier than the DA or 3-step method. And since there is only 4 numbers to remember, it's pretty easy!

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The way I got 36 minutes from 0.6 is multiplied 0.6 by 60 since there are 60 minutes in an hour. This is the way I do all of my questions like this.

Hope this helps!!

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Specializes in critical care; community health; psych.

That magic number formula is pretty cool. I never heard of it before.

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Specializes in DNAP Student.

Just my 2 cents....

I still wonder why nursing schools gives drip calculation questions using macro, micro drip what so ever. All hospitals have pumps and pumps are more precise in running IV drips the manually adjusting it for 60 gtts/min.

I know we still need to calculate for dosages before adminsitering drugs but questions with macro and micro drips in it hmmm... in the real world you use infusion pumps and you run the IV as ordered....

just wondering....

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Specializes in Emergency Dept, M/S.
Just my 2 cents....

I still wonder why nursing schools gives drip calculation questions using macro, micro drip what so ever. All hospitals have pumps and pumps are more precise in running IV drips the manually adjusting it for 60 gtts/min.

I know we still need to calculate for dosages before adminsitering drugs but questions with macro and micro drips in it hmmm... in the real world you use infusion pumps and you run the IV as ordered....

just wondering....

I wondered the same thing, and my professor said it's because if you end up doing field work - in-the-field trauma, flight nursing, occupational health, etc., you would not have access to a pump. Actually when I was in the ER last December a couple times for a stomach virus I couldn't kick, they didn't have pumps there either. It wasn't until I was admitted that they put me on a pump. I don't know if all ER's are like that, but this is a podunk, small-town, community hospital with no trauma center.

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Specializes in ER, PACU.
Just my 2 cents....

I still wonder why nursing schools gives drip calculation questions using macro, micro drip what so ever. All hospitals have pumps and pumps are more precise in running IV drips the manually adjusting it for 60 gtts/min.

I know we still need to calculate for dosages before adminsitering drugs but questions with macro and micro drips in it hmmm... in the real world you use infusion pumps and you run the IV as ordered....

just wondering....

In the fantasy land you are imagining there are pumps everywhere and you never need to calculate..But back here on earth there will be MANY times when you cant find a pump for a patient, or you only have X number of pumps available to you/your unit, and you/your coworkers need it for your/thier patients on dopamine/heparin/nitro/nipride gtt, so using up a pump for a patient that is getting antibiotics or fluid is just not going to fly. I am not saying that you are wrong by stating that fluid should be on a pump, and in some cases like in peds or a CHF patient they should be, but there is greater harm in trying to calculate a medicated drip using the drop method than there is regular IV fluid, so if there are limited pumps available, you must use them for the drips instead.

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