Hi, this is Cathy with Level Up RN. In this video, I will be going over a variety of dosage calculation problems that involve delivering IV fluids using gravity as opposed to a pump. I will first go over how flow rate is regulated using gravity, explain what a drop factor is, and then share the different types of IV tubing used when delivering IV fluids through gravity. I will then work through a variety of problems on my whiteboard using both dimensional analysis and ratio and proportion. 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 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.
So regulation of flow rate when you use gravity is done by using the roller clamp on the IV tubing and watching the drops in the drip chamber. In order to calculate the drops per minute, you need to know the drop factor of the IV tubing that's being used. So drop factor is the number of drops in one ml of solution. And IV tubing for delivering IV fluids through gravity can either be macrodrip tubing or microdrip tubing. Macrodrip tubing delivers 10, 15, or 20 drops per ml. Microdrip tubing delivers 60 drops per ml. So when you are given a gravity problem, if the patient is using-- or the nurse is using macrodrip tubing for that patient, you will be told what the drop factor is. So they'll tell you the tubing has a drop factor of 10 drops per ml or 15 drops per ml. However, sometimes they'll tell you on a dosage calculation problem that microdrip tubing is being used, and they may not give you a drop factor. So you need to memorize the fact that with microdrip tubing, this delivers 60 drops per ml. So that's something you've got to remember because you will not always be given that information.
Let's work through our first example problem that pertains to IV infusions delivered through gravity. So with this problem, we have an order for 500 milliliters of normal saline to infuse over four hours. And we have IV tubing with a drop factor of 10 drops per ml. And we want to find out how many drops per minute should be delivered to the patient, and we should round our answer to the nearest whole number. So the most efficient way to solve this problem is with dimensional analysis, so I'm going to solve it using dimensional analysis first. So I'm going to start by writing down kind of what is ordered, and what's ordered is 500 milliliters of normal saline to be delivered over four hours. But I don't want milliliters per hour, right? I want drops per minute. So I'm going to need to multiply times conversion factors to get to that. So I know I can change hours to minutes easily. So one hour over 60 minutes, my hours cross off, and now I have milliliters per minute. But I need drops per minute. So now I'm going to multiply times the drop factor here, which is 10 drops per one ml. And my mls cross off here. And if I calculate this out, I am left with drops per minute. So if you do that, you end up with 20.8333 and on and on and on, so the three is repeating. So we need to round this to the nearest whole number, so that will end up being 21 drops per minute. Okay. So that is the answer using dimensional analysis.
With ratio and proportion, it definitely takes a couple more steps to figure it out. So again, we want 500 milliliters delivered over four hours, but we need to know-- we want this to actually be drips, and we want this to be minutes, right? So we know how to convert four hours to minutes, right? So four hours is really equal to 240 minutes. But we need to figure out how many drops are in 500 ml, and we can do that by setting up our ratio. So we know there are 10 drops in 1 ml, and we want to know how many drops are in 500 ml. So if we cross-multiply here, we end up 1 times X is X. 500 times 10 is 5,000. So there are 5,000 drops in 500 ml, so 5,000 drops. So if I take 5,000 drops and divide that by 240 minutes, then I will get the same answer I did here. So it'll be 20.83 with the three repeating, which we would round up to 21 drops per minute. And that's the answer to this problem.
Well, let's work through our next example problem. With this problem, we have an order for 50 milliliters of normal saline to infuse over 30 minutes using microdrip tubing. How many drops per minute should be delivered to the patient? Round to the nearest whole number. So you will notice they told us that we have microdrip tubing. They did not give us the drop factor. That is because you sometimes need to memorize what the drop factor is for microdrip tubing. And if you recall, it is 60 drops per ml. That is the drop factor there. So we need to calculate the drops per minute that needs to be delivered to the patient. So let's first calculate that using dimensional analysis. So we have 50 ml that we want to give over 30 minutes. But we want to find out how many drops per minute should be delivered, so we're going to multiply this times the drop factor, so 60 drops per ml. And our mls will cross off. And if we calculate this out, we end up with 100 drops per minute. And this is already rounded to the nearest whole number, so we're good as far as rounding. So that's how you would solve it with dimensional analysis.
With ratio and proportion, again, we want to give 50 ml in 30 minutes. But we need to figure out how many drops is this, right? We want drops and not mls. So we're going to set up a ratio. So our drop factor is 60 drops for 1 ml, and we want to find out how many drops are in 50 ml, right? So we want to make this drops instead of mls. So we do our cross multiplication here. 1 times X is X. 60 times 50 is 3,000. So if we take 3,000, and this will ends up being 3,000 drops. So 3,000 drops divided by 30 minutes will give us 100 drops per minute, so same answer as we got above using dimensional analysis. This is a little faster and more efficient, but this is another solid way to solve this problem.
All right. Let's work through our next example problem. In this problem, we have an order to infuse 1,000 milliliters of normal saline at 20 drops per minute. And we have IV tubing with a drop factor of 15 drops per ml. What is the infusion time in hours for the above order? Round to the nearest 10. Okay. So we're going to solve this with dimensional analysis first, and then we're going to do it with ratio and proportion. Definitely more efficient to use dimensional analysis for this one. All right. So dimensional analysis. So we have 1,000 milliliters of normal saline, and we are trying to get to hours. So we're going to just multiply times different conversion factors to get us there. So we've 1,000 milliliters. We have a drop factor of 15 drops per ml. And our mls will cross off. Now we're at drops. And we're going to be infusing this at 20 drops per minute. And I purposely put the drops on the bottom of the ratio because I want my drops to cross off. Now I'm in minutes, but the question is asking for hours. So then I would multiply times this conversion factor. So my minutes cross off, and I am left with hours. So if you calculate that out, we end up with 12.5 hours. And that is already rounded to the nearest 10. So you can see this is really where dimensional analysis kind of shines. You could solve it all in one equation, kind of in one step. You just have to be really careful about your units so that like units cross off, and you're left with the units that you are looking for. It matters what's on top and what's on bottom.
Now let's work through this same problem using ratio and proportion. It will definitely take a few more steps with this method. So the first thing we need to figure out is how many drops are in 1,000 ml, which is what we need to deliver to our patient. So we can do this by setting up a ratio. So we have 15 drops in 1 ml, and we're wondering how many drops are in 1,000 ml. So if we cross-multiply here, 1 times X is X. 15 times 1,000 is 15,000. So we have 15,000 drops that are in 1,000 ml. So we need to give this 15,000 drops at a rate of 20 drops per minute, okay? So if I take my 15,000 drops and divide that by 20 drops-- not 2, 20 drops, then I'll figure out how many minutes it will take to deliver this volume. So if I do this math, I end up with 750 minutes. But we weren't asked for minutes. We were asked for hours, so we need to convert this to hours. And if we do that, divide by 60, we end up with 12.5 hours, which is what we had here above. So a few more steps, definitely more efficient. But this method just makes more sense to certain people, and that's fine. And that's that for that example.
All right. Let's work through our last example problem of IV infusions that are delivered via gravity. So in this problem, we have normal saline being infused at 30 drops per minute using IV tubing with a drop factor of 10 drops per ml. And we want to know how many milliliters are infused over four hours round to the nearest whole number. So definitely the fastest way to do this problem-- to solve this problem is with dimensional analysis, so that's the way I'm going to do it first. And then I will solve it with ratio and proportion as well. So we are trying to get to milliliters. So when it comes to dimensional analysis, you basically just keep multiplying times things to get to the units you are looking for. So let's just go ahead and start with our rate, which is 30 drops per minute. And if I multiply this times the drop factor, which is 1 ml over 10 drops, I purposely put the drops on the bottom so that my drops can cross off. Now I'm to milliliters per minute. We're getting there. So then I am going to multiply this times a conversion factor to get to hours because I want to make sure I'm factoring in the four hours of infusion time. So 60 minutes equals one hour. So now my minutes cross off, and I have milliliters per hour. And now, if I multiply it times four hours, my hours will cross off, and I will be left with milliliters, which is exactly what I was looking for. So if we multiply this out, we end up with 720 milliliters, which is rounded to the nearest whole number as instructed.
Let's now solve this problem with ratio and proportion, which will take a few more steps. So we want to figure out-- let's first figure out how many minutes are in four hours, because then we can figure out how many drops are being delivered to the patient within those four hours. So four hours equals 240 minutes, right? And we have an infusion rate of 30 drops per minute, so that can be one side of our equation. And then we can find out how many drops are delivered over 240 minutes, which is those four hours. So I would do my cross multiplication here. 1 times X is X. And then 30 times 240, that equals 7,200 drops. So 7,200 drops are being delivered over four hours. But we need to figure out how many milliliters are being infused over those four hours. We can figure that out by using our drop factor. So our drop factor is 10 drops per ml, so if I divide that by 10 drops per ml, I will get 720 ml. And that is the volume in milliliters that's being infused over four hours.
