Welcome to two examples
of determining the drops per minute of an IV.
To determine the drops per minute,
we're going to multiply the flow rate
in milliliters per hour
by the drop factor
and then divide by 60 minutes per hour.
This will give us the drops per minute.
And the drop factor is the number of drops
it takes to equal one milliliter
with a specific type of IV tubing.
Before we take a look at our first example though,
I do want to show why these units
work out to drops per minute.
If we start with milliliters per hour,
which I'll write in fraction form,
and multiply this by the drop factor,
which is in drops per milliliter,
and then we divide this product by minutes per hour,
notice how the units of hours simplifies out
as well as the units for milliliters,
leaving us with drops per minute.
Now, let's go and take a look at our first example.
The drop factor is 20 drops per mil
and the flow rate is 150 mil per hour.
Find the drops per minute.
So we'll have the flow rate in milliliters per hour,
which is 150
milliliters per hour,
times the drop factor which is 20
drops per mil,
and we're going to divide this by
60 minutes per hour.
Now, we could find this product and then divide,
but I'm going to encourage you to simplify it first.
The two most common drop factors are 15 and 20.
Well, if we have a 20 here in the numerator
and a 60 here in the denominator,
notice how these two do share a common factor of 20.
Therefore, we can simplify the 20 to one,
and there are three 20s in 60,
so we can simplify this to three.
So this would simplify nicely to
150 divided by three,
which we know is going to be drops per minute.
And now we'll go ahead and find this quotient.
By hand, we would have 150
divided by three.
There are five threes in 15,
five times three is 15.
Subtract,
bring down the last digit of zero.
There are zero threes in zero.
Zero times three is zero,
we subtract, we have zero.
So our final answer would be 50 drops per minute.
Let's go ahead and check this on the calculator.
Of course, with a calculator
it's not as important to simplify it first.
Let's verify both of these.
Let's first do 150
times 20
in parenthesis
and then divided by 60,
which was the original set up.
Still 50.
Or 150 divided by three.
Of course, it's still 50.
Let's take a look at another example
where we actually have to round.
Here, the drop factor is 15 drops per mil
and the flow rate is 145 mils per hour.
So to find the drops per minute,
we would have the flow rate in milliliters per hour,
which is 145
milliliters per hour,
times the drop factor which is 15 drops per mil,
and we're going to divide this by 60 minutes per hour.
Again, before we work this out though, let's simplify it.
Looking at just the 15 and the 60,
since 15 times four is 60,
we can simplify the 15 to one,
there's one 15 in 15 and four 15s in 60.
So now we could write this as
145 divided by four
drops per minute.
This quotient will be much easier to find by hand
than multiplying and then dividing.
145
divided by four.
There are three fours in 14,
three times four is 12,
we subtract, difference is two,
bring down the five.
There are six fours in 25.
Six times four is 24,
we subtract, the remainder is one.
We want to round this to the nearest drop or whole number.
So we'll have to go to the one decimal place to determine
whether round up or down.
So put a decimal point here, bring it up with the quotient,
add a zero and bring it down.
There are two fours in 10.
Two times four is eight,
subtract which gives two.
We can stop here, the two tells us to round down,
which means this would be approximately 36
drops per minute.
Again, let's go ahead and verify this on the calculator.
Originally, we had 145
times 15
and then divide all of this by 60.
Again, this rounds to 36.
Or the simplified form of 145
divided by four will give us the same quotient.
I hope you found this explanation helpful.