- 00:00
- 2:00 Example 1
- 3:11 Example 1A Dimensional Analysis
- 4:59 Example 1B Dimensional Analysis
- 5:48 Example 1C Dimensional Analysis
- 7:26 Example Ratio & Proportion
- 7:43 Example 1A Ratio & Proportion
- 9:46 Example 1B Ratio & Proportion
- 11:04 Example 1C Ratio & Proportion
- 13:07 Example 1A Formula method
- 15:15 Example 1B Formula method

# Dosage Calc, part 27: Maternity Oxytocin

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## Full Transcript: Dosage Calc, part 27: Maternity Oxytocin

## Full Transcript: Dosage Calc, part 27: Maternity Oxytocin

Hi, this is Cathy with Level Up RN. In this video, I'll be working through several dosage calculation problems that involve the administration of oxytocin. And I'll be solving these problems on my whiteboard using three different methods, including dimensional analysis, ratio and proportion, and the formula method. You can find all the information that I'll be covering in this video in our Level Up RN dosage calculation workbook. If you are in nursing school, then you know how important it is to master dosage calculations. And our workbook will help you do just that. In a nutshell, our workbook contains all the different types of dosage calculation problems that you are likely to encounter in nursing school. And we demonstrate how to solve each problem using multiple methods so you can pick the way that makes the most sense to you.

Oxytocin is a uterine stimulant that is used to induce labor as well as control postpartum bleeding. So oxytocin comes in units per mL, and it is prescribed in milliunits per minute. And we would titrate that rate, meaning we would increase or decrease that rate per the order. So I first wanted to mention that milliunits is not a unit of measure that you see all the time. But we're going to handle it in just the same way as we would another unit of measure that we would see more frequently, like milligrams. So don't get freaked out when you see milliunits because it's just another unit of measure. We're not doing anything different. And just keep in mind that 1,000 milliunits is in one unit. So that is a conversion factor that we will definitely need as we are solving this problem.

All right. Let's look at our problem. So our patient is currently receiving Lactated Ringers at 125 milliliters per hour. We have an order to hang oxytocin, IV piggyback starting at 2 milliunits per minute, and to increase the infusion rate every 30 minutes by 2 million units per minute if there are no signs of fetal distress. Pharmacy sends us 10 units of oxytocin in 1,000 milliliters of normal saline, and we need to round all of our answers to the nearest whole number. Okay. So we are going to solve these three problems using dimensional analysis first because it's the most straightforward and efficient way to solve these problems. Then after I'm done with that, I will go through and solve them all with ratio and proportion as well. You can solve some of these with the formula method but not all.

So let's first go through this problem using dimensional analysis. All right. So with dimensional analysis, let's start with question A. What is the initial rate in milliliters per hour? So let's start by writing down the ordered rate, which is two milliunits per minute. So with dimensional analysis, we're going to keep multiplying by conversion factors to get to the units we are looking for, which is milliliters per hour. So I already know I need to go from minutes to hours. So I'm going to multiply times this conversion factor, right, 60 minutes in an hour. And that gets me to milliunits per hour. Now I need to try to get to milliliters. And the way I'm going to do that is I'm going to be multiplying by our available concentration here, 10 units in 1,000 milliliters. But you notice this is 10 units and not milliunits. So my next step here is to multiply by this conversion factor. One unit equals 1,000 milliunits. And I purposely put units on top, milliunits on the bottom such that they cross off here.Now I'm ready to multiply by our available concentration. So that is 1,000 milliliters and 10 units. And I purposely put my units on the bottom so that they'll cross off here. And when I multiply this out, I'll be left with milliliters per hour. So if you do that, you end up with 12 milliliters per hour. Okay? And that's the answer to A.

Now, B asks us, what is the infusion rate in milliliters per hour when the patient is receiving 8 milliunits per minute? Well, guess what? I can actually just change this 2 milliunits per minute here to 8 and rerun that math to get the milliliters per hour. So we're going to do that. So I'm just going to erase my answer there, erase my little 2 here, change that to 8, and then rerun this math. I end up with 48 milliliters per hour. Okay? So that was easy enough, right? We already did all the hard work in part A, so we just took advantage of that. And this is the answer to Part B here.

Part C, if the pump is set to 30 milliliters per hour, how many milliunits per minute of oxytocin is the patient receiving at that time? So we kind of have to work our way backwards from what we did here in Part A and Part B. So we'll start by writing down the rate, which is 30 milliliters per hour. And we are trying to get to milliunits per minute. So let's go ahead and convert our hours to minutes, right, making sure to put the hours on top so that they cross off here. Now I can multiply by our available concentration, which is 10 units in 1,000 milliliters. So I have 10 units in 1,000 milliliters. I made sure my milliliters are on the bottom so that they cross off here. Now I have units per minute, but I need milliunits per minute. So I would go ahead and multiply by this conversion factor, right, 1,000 milliunits in one unit so that my units cross off. And now when we multiply this out, we'll end up with milliunits per minute. So if I do this, I end up with 5 milliunits per minute. And that is the answer to part C of this problem.

All right. Let's answer these same three questions using ratio and proportion. It's definitely going to take multiple steps to use this method. So if dimensional analysis made sense to you, then I would probably skip over this part of the video. But if you like ratio and proportion, I'm going to work through that now. All right. So for part A, we are being asked, what is the initial rate in milliliters per hour? So our ordered rate is 2 milliunits per minute, and we're trying to get to milliliters per hour, right, instead. So we want to find out how many milliliters is required for 2 milliunits. So we're going to set up our ratio. We're going to start by putting down our known concentration on one side of the equation. So 1,000 milliliters has 10 units, right, which is right here. Then on this side, we want to know how many milliliters is 2 milliunits. But I need to make sure I have units, right? I need to have milliliters, milliliters, units, units. So I'm going to take this 2 milliunits and convert it to units. So that is 0.002 units.

And so that's what I'm going to put down here. And we're going to solve for X. So we're going to cross multiply here. 10X equals 1,000 times 0.002. So that is 2. And then X equals 2 divided by 10. This equals 0.2 milliliters. So we know that for 2 milliunits, this is 0.2 milliliters. So we have 0.2 milliliters per minute, but we want milliliters per hour. So we're going to multiply this times the 60 minutes, which is an hour, right? 60 minutes is in one hour. And if you multiply this out, you end up with 12 milliliters per hour. So that is the rate and the answer to A.

All right. Let's look at Part B now. Part B is asking us, what is the infusion rate in milliliters per hour when the patient is receiving 8 milliunits per minute? So pretty much, it's the same thing except with 8 milliunits per minute versus 2. So we're going to convert our 8 milliunits to units. So that's going to be 0.008 units. And then we're going to set up our ratio. So our known ratio is on one side, right, which is our available concentration. And then our unknown value, milliliters, is on the other side, 08 units. And we're going to cross multiply, solve for x, and we would end up with 0.8 milliliters. And just like we did over here, we have 0.8 milliliters being infused per minute. To get to milliliters per hour, I would need to multiply it times 60. And that would give us 48 milliliters per hour. And that is the answer to part B.

All right. Let's now solve part C, which is asking us if the pump is set to 30 milliliters per hour, how many milliunits per minute of oxytocin is the patient receiving at that time? So our patient is getting 30 milliliters per hour, and we want to get to milliunits per minute, right? So let's go ahead and set up our ratio. We'll take our known concentration, which is 10 units in 1,000 milliliters. And we want to find out for 30 milliliters, right here, how many units is that? Okay? So we're going to cross multiply. That's 1,000X equals 300. If we solve for X, that equals 0.3 units. But we actually need milliunits, right, not units. So we're going to convert this to milliunits. So we're going to move the decimal point to the right three places. So that's 300 milliunits. So now we know we have 300 milliunits in 30 mL, so 300 milliunits per hour. But we want to know how many milliunits per minute. So we need to divide this by 60, right? Because there are 60 minutes in one hour. So 300 divided by 60 equals 5 milliunits per minute. And that is the rate in milliunits per minute if our pump is set to 30 milliliters per hour.

All right. Let's work through at least a couple of these problems with the formula method. So formula method is up next now. Part A asks us, what is the initial rate in milliliters per hour? So our ordered rate is 2 milliunits per minute, and we want to get to milliliters per hour, right? So we need to figure out how many milliliters do we have to milliunits in. So we are going to set up our formula, which is desired over half times the vehicle. But before we can do that, I need to convert my milliunits to units. So 2 milliunits equals 0.002 units.

And the reason I have to do this is when I set up my formula-- so desired is this 0.002 units. Have is 10 units. And our vehicle is 1,000 milliliters. And you can see the reason why I had to do this is because I need this unit of measure and this unit of measure to be the same. So that's such that our units will cross off, and we can multiply this out and get milliliters. So this ends up being 0.2 milliliters. So now we know we have 0.2 milliliters that needs to be infused per minute. But we really want hours, right? So we're going to have to multiply this times 60 minutes to get our hours. So when we do that, we end up with 12 milliliters per hour. And that is the rate for part A. So you can see with the formula method, I had to do this conversion and then use the formula and then do another little conversion. So it's definitely multiple steps as opposed to dimensional analysis, which was one equation.

All right. Part B is asking us, what is the infusion rate in milliliters per hour when the patient is receiving 8 milliunits per minute? So we're pretty much doing the same exact calculation, but we're using 8 instead of 2. So 8 milliunits equals 0.008 units. And then now I can set up my equation. So have-- I'm sorry, desired equals 0.008 units. And what we have is 10 units in 1,000 mL of solution. And if we multiply this out, we end up with 0.8 mL. Then just like we did here, 0.8 mL per minute, we need to convert that to milliliters per hour. So we're going to multiply it by 60, right, to get our 48 milliliters per hour because there are 60 minutes in an hour. So the answer to B is 48 milliliters per hour. So because the formula method requires us to do desired over have times vehicle, there is not a way to solve this last part of the problem where that makes sense. So you'll need to use either dimensional analysis or ratio and proportion to solve part C of this problem versus the formula method.