Hi, this is Cathy with Level Up RN. In this video, I'll be working through a dosage calculation problem that involves heparin titration. And I'll be working through this problem 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 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.
In this problem, we have an order for heparin 5,000 units IV bolus to be administered, and then a continuous IV infusion that should be titrated based on the patient's aPTT level using the protocol, which I'm going to show you here in a minute. Our initial infusion rate is 18 units per kilogram per hour, and we need to round all our answers to the nearest tenth. What we have available to us is heparin 25,000 units in 500 ml, and our patient weighs 176 pounds, and has an initial aPTT level of 35 seconds.
So before we get into the first set of questions, let's take a look at our heparin protocol. All right. Here is our heparin protocol. This is a pretty standard protocol that you would see across many hospital systems, but of course, you would want to refer to your facility's policy and your facility's particular heparin drip protocol. So with this protocol, we have three columns. The first column is where you would look up your patient's aPTT level. The second column will tell you whether you need to administer a bolus dose for your patient, depending on their aPTT level. So you can see, in some cases, we don't want to administer a bolus, and in other cases, we're given a bolus dose in units per kilogram. And then our third column tells us whether we need to adjust our heparin infusion rate based on the patient's aPTT level. So we always want to get our patient's aPTT level prior to initiating therapy. And then we want to get a repeat aPTT level every six hours, and then we would use that level to look up whether we need to administer a bolus dose and/or adjust the infusion rate. When we get two consecutive aPTT levels that are within the ideal range, which is between 60 and 100, then we can start drawing the aPTT level every morning as opposed to every six hours.
Let's go ahead and work through part A of our problem. Part A asks us, what is the starting infusion rate in milliliters per hour? And if you look at our order, the initial rate is ordered in units per kilogram per hour. So we know right out of the gate, we're going to need to know our patient's weight in kilograms instead of pounds. So let's go ahead and figure that out. If we take 100-- my marker could work here. There we go. If we take 176 pounds, divide by 2.2, or multiply by the conversion factor, which is 1 kilogram equals 2.2 pounds, I end up with 80 kilograms. So that is my patient's weight in kilograms. Now, I can go ahead and try to solve this problem. I can use either dimensional analysis, ratio and proportion, or the formula method to solve part A.
So let's first use dimensional analysis, which is definitely the most efficient and straightforward way to solve this problem. So with dimensional analysis, I can take my patient's weight in kilograms, and I can multiply by the initial infusion rate from the order. So that's going to be 18 units per kilogram per hour. And you'll see that my kilograms will cross off, and I'm left with units per hour. So what I'm looking for, though, is milliliters per hour. So if I take this and multiply by the available concentration, making sure to put milliliters on top and my units on bottom, such that my units cross off, and I'll be left with milliliters per hour, that's what I'm looking for. So if you do this math, we end up with 28.8 milliliters per hour, and this is rounded to the nearest tenths place per the instructions of the problem.
Let's now work through this problem using ratio and proportion. With ratio and proportion, we actually have to do a few steps before we can set up our equation with the ratios. So we need to take the patient's weight, 80 kilograms, and multiply it by the initial ordered rate, which is 18 units per kilogram per hour. And if we do this math, we end up with 1,440 units per hour as the initial rate, but we want milliliters per hour. So through ratio and proportion, we need to figure out how many milliliters it will take to give the patient 1,440 units. So on one side of the equation, we're going to put our known ratio, which is 25,000 units in 500 ml. That's our known ratio, basically our concentration. And on the other side of the equation, we're going to put the amount of units we're looking for and an X for the ml. That's our unknown value and what we're looking for. So now we're going to cross-multiply here. We're going to end up with 25,000 X equals 500 times 1,440. And then if we solve for X, we're going to end up with 28.8 milliliters. So in order to give the patient 1,440 units, it's going to take 28.8 milliliters. So our rate is going to be 28.8 milliliters per hour. Okay, so we get to the same answer as we did with dimensional analysis, just a few more steps.
With the formula method-- I'm going to erase this work here and now do the formula method. We actually need to do this first initial step with the formula method as well. So I won't redo that, but basically, we're taking the patient's weight, multiplying that by the initial ordered rate, and we end up with units per hour. So 1,440 units per hour. But we want milliliters per hour, so we need to figure out how many milliliters will it take to give the patient 1,440 units. So with the formula method, we have desired over have times the vehicle. So what we desire is 1,440 units, and what we have are 25,000 units in 500 ml of solution. So if we do this math, we end up with 28.8 milliliters. This is the amount that will need to be given over an hour. So the rate will be 28.8 milliliters per hour.
Okay. So that is part A, solving it three different ways. Let's look at Part B. Part B is asking us six hours after heparin was initiated, our patient's aPTT is now 39 seconds. Will a bolus be administered? If so, how many units will be given? And then in addition, in part C, we're being asked, will the rate be adjusted? If so, what is the new rate in units per hour? So now we need to use our heparin protocol, and we need to use our patient's aPTT level of 39 seconds and see if we need to administer a bolus and if we need to adjust the rate. All right. So our patient has an aPTT of 39, which means they fall within this range under 40 seconds. If we look over here, we will need to administer a bolus dose of 80 units per kilogram, but we have a maximum of 5,000 units that we can administer with the bolus dose. In addition, we need to increase our patient's infusion rate by 3 units per kilogram per hour.
All right. So according to the protocol, we need to give the patient a bolus dose of 80 units per kilogram. So if we take this and multiply it by the patient's weight, 80 kilograms, we get 6,400 units. However, according to the protocol, the max bolus amount is 5,000 units. So we are not going to give 6,400 units. We're going to give the maximum amount of 5,000 units. All right. So that is going to be our bolus dose.
How about the rate from part C? Will the rate be adjusted? Well, according to the protocol, we need to increase our rate by three units per kilogram per hour. So our initial rate was 18 units per kilogram per hour. So now our new rate is going to be 21 units per kilogram per hour, but we need to get that into units per hour for this question. So we're going to multiply this by the patient's weight, 80 kilograms, and this will give us 1,680 units per hour. So that is going to be the new rate in units per hour per the protocol.
Let's now look at parts D and E of this problem. So D says, "Six hours later, the aPTT is now 102 seconds. Will a bolus be administered? If so, how many units will be administered?" And then E says, "Will the rate be adjusted? If so, what is the new rate in units per hour?" So let's take a look at our heparin protocol with our new aPTT of 102 seconds. For an aPTT of 102, our patient would fall within this range right here, between 101 and 110. This means we would not give a bolus to our patient, and we also need to decrease their infusion rate by one unit per kilogram per hour. All right. So for part D, we will not be administering a bolus, so no bolus. And for Part E, we will be adjusting the rate. So according to the protocol, we need to take the rate down by 1 unit per kilogram per hour. Our previous rate was 21 units per kilogram per hour, so our new rate is going to be 20 units per kilogram per hour. I don't know why my pen's so squeaky now, but anyway. So if we take this new rate, and we multiply by the patient's weight, which is 80 kilograms, then our kilograms will cross off here. And if we multiply this out, we end up with 1,600 units per hour. And that is the new rate in units per hour, and that concludes our heparin titration example problem.
