Now, you can see what we have left after we cancel is mL on the top and hr on the bottom – everything else is cancelled, so we are good to go! Over here, we wrote what we’re looking for – mL/hr. Remember our goal here is to cancel units until we end up with what we are looking for. So now I have mEq on top and bottom, so it cancels. So what I know is 60 mEq – and what about that 60 mEq? It needs to go over 4 hours. So – I’ve already used THIS mEq – so now I need to use the other one. Sometimes I find it helpful to cross out information once I’ve used it because we won’t use it again. Now we have mEq down here – transfer the units up – insert what we KNOW about mEq. ![]() So, now we have liters on top and bottom and it cancels. Then insert what we KNOW about liters – what we KNOW is that in 1 L of NS, there is 100 mEq of KCl. So now we transfer units – put liters up here. So we’ve already got our first 1,000 mL equals 1 L. Remember, if you see the same units on the top and the bottom on this side of the equation, they will cancel. We’re going to repeat this process of transferring units across, inserting what we know, and converting if we don’t UNTIL we can cancel enough units out to find what we’re looking for. Now – here’s where we really start to build out this problem… So we’re going to convert – 1,000 mL equals 1 L. Do we have anything in here that could use a conversion? Yes – we have Liters. So – if you don’t KNOW anything about that unit – we use a conversion. So – does the problem say anything about milliliters? Actually – no. What I mean by what you KNOW is if you have anything provided about those units. Once we’ve transferred our units over, the next step is one you’ll just keep repeating – insert what you KNOW, convert if you don’t. This will help set us up for success so that we know we end up with the right units in the right place. So, in this case, we’re going to take the mL from the left and shift it directly over to the right. Once you’ve got that, the next step is to transfer the units across. ![]() Okay – step 1 – start with what you’re looking for. What is the rate you should set on the pump? So first things first – identify our variables – what are we looking for? Setting a rate on an IV pump always means mL per hour – so write that here, then write an equals sign because we’re going to be setting up an equation. The provider orders 60 mEq of KCl IV to be given over 4 hours. So when you start dimensional analysis, you always start with what you’re looking for and build your equation from there. ![]() In the other med math lessons on the different types of problems, we will use this method, because we honestly feel like it’s the best way to go. We’re going to talk you through the process of dimensional analysis with the same problem we used in the Basics of Calculations lesson, then I’m going to show you how it work for simple AND complex problems by working a few out. Everything happens with ONE final calculation. And – while we think we’ve done a pretty good job breaking that down for you in the basics of calculations lesson, we still believe that having only one way to do things every time is way better! The other benefit is that dimensional analysis works for all types of calculations – simple, complex, weight based, lots of conversions or super straight forward – it still works! And there’s no need to do any separate conversions or rounding in the middle of the process. Other ways teach you multiple different formulas to learn. The biggest benefit I see to dimensional analysis is that it means you only have to know ONE process. I wrote med math made easy here because we honestly believe that dimensional analysis is the best way to go when it comes to dosage calculations. In this lesson we’re going to talk about dimensional analysis.
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