Drug Calculations – total infusion time  105

Drug Calculations – total infusion time 105


This video is provided as supplementary
material for courses taught at Howard Community
College and in this video I want to show how to calculate the
total infusion time for an IV. Here’s the first problem. A 300 milligram IV is ordered
to be given at the drip rate of 25 milligrams per minute. How long will it take to infuse the
medicine? So let’s start out with the order
that we have, how much medicine we have to give.
That’s 300 milligrams. I’ll make that the the beginning of the left side
of the equation, and since I’ll be dealing with fractions I’ll make that into a fraction. I’ll put it
over 1.I know that I’m dealing with time, so on the right side of the equation I’ll leave a space for the answer and write
minutes. The other information is that the drip rate is 25 milligrams
per minute. Since I want to end up with
minutes I’m going to multiply that amount that’s ordered, the 300 milligrams by
the fraction minutes over 25 milligrams. By putting the
minutes in the numerator, I’ll end up with minutes in my
answer, and I’ll be able to cancel out the milligrams.
So let’s do that. We’ll cancel out the milligrams.
I’ve got a 300 and 25, so I can reduce those numbers.
I’ll divide both by 25. 300 divided by 25 is 12, and 25 divided by 25 is just 1. Now I’ve only got 1’s in the
denominators, so I don’t have to worry about them.
I’ll just multiply the numerators. That’s going to be 12 times minutes.
So that’s going to be 12 minutes. Let’s do one more. This one says the
order is for 1000 milliliter. to be infused at a rate of 50 drops per
minute. If you drop factor is 15, how long will
it take to infuse the medication? So let’s take the amount order,
1000 millimeters. I’ll write that down. Once again
I’ll make it into a fraction. I’ll put it over 1. On the right side of the equation I want to
write the units that I’ll be left with. I want to be left with time,
so that’s minutes. Now let’s add the rest of the information.
The rate we’re dealing with is 15 drops per minute.
So once again I’ll put minutes in the numerator
and I’ll take that 50 as the denominator. And the last thing I know is
that the drop at factor is 15. So that’s like 15 gtt over 1 milliliter. 15 drops.
So here’s 15 gtt over 1 milliliter. This time I want the
drops in the numerator so I can cancel out the ones
in the denominator over here. And I’ll also be able to cancel the
milliliters. Now let’s cancel those units. The milliliters are going to cancel and the gtt, the drops will cancel. I can simplify the numbers a bit. I’ve got a 50 over here and 1000 here, so let’s start by dividing by 10.
I’ll just cross out a zero in each number, and I can
divide the 100 by 5 and I’ll divide the 5 by 5.
So 100 divided by 5 is 20 and 5 divided by 5 is 1. Once again I’ve got only 1’s in the denominator. I’ll just multiply across
the numerators and see what we end up with. l
So that’s 20 times minutes times 15.
20 times 15 is 300. So that’s 300 minutes. With a number like this, I don’t want to leave that minutes. I want to convert that to hours.
So let’s remember that there are 60 minutes in an hour.
So that’s 300 minutes times one hour over 60 minutes. The minutes will cancel out.
I’ve got 300 and 60. I’ll divide them both by 10
to begin with. I’ll cross a zero off each one. And I can divide both 30 and 6 by 6.
30 divided by 6 is 5 and
6 divided by 6 is 1. I’m going to be left with 5 hours. To review quickly, what I did was I
started out with the amount of medication that was ordered. I took the rate that we’re
infusing it at, 50 drops per minute and I put the minutes in the numerator
so I would end up with minutes and the drops in the denominator.
And I was given a drop factor also. So I had to multiply by the
drop factor, which was 15 gtt, 15 drops per milliliter. I cancel out
whatever units I can, multiply across. I end up with 300 minutes. Since that’s a large number of minutes, I want a convert it to hours.
So I use the conversion from minutes to hours and up with 5 hours. So that’s about it. Take care. I’ll see you next time.

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