Ep 92 Pre-Reg Practice Question 2 - Pediatric Pharmacology Calculations

While the UK and United States have different methods for assessing their health professionals often the calculations and math(s) strategies are the same. I invite you to enjoy this 12-part series on Part 2 of preparing for the Pre-Reg exam but will also help those in the states that are looking to improve their skills in nursing, pharmacy technician, and pharmacist skills. Here's the Memorizing Pharmacology book link: https://www.audible.com/pd/Memorizing-Pharmacology-Audiobook/B09JVBHRXK?source_code=AUDFPWS0223189MWT-BK-ACX0-281667&ref=acx_bty_BK_ACX0_281667_rh_us

Want more options?

Find the book here: https://geni.us/iA22iZ 

and subscribe to my YouTube Channel  TonyPharmD here: https://www.youtube.com/c/tonypharmd

Here is the Link to my Pharmacy Residency Courses:  residency.teachable.com

Auto Generated Transcript:

Welcome to the Memorizing Pharmacology podcast. I’m Tony Guerra, pharmacist and author of the Memorizing Pharmacology book series, bringing you mnemonics, cases, and advice for succeeding in pharmacology. Sign up for the email list at memorizingfarm.com to get your free suffixes cheat sheet or find our mobile-friendly self-paced online pharmacology review course at residency.teachable.com/p/mobile. Let’s get started with the show.

I’ll just read it. The following hospital prescription is written for a seven-year-old child weighing 24 kilograms. The one translation I made or conversion factor I created was reminding you what 10 really means when you have a weight per volume. It’s 10 grams per 100 mLs, so you know 20 would be 20 grams per 100 mLs, and then 0.5 grams per kilogram. Normally I use yellow, but for whatever reason yellow didn’t come up against that gray background.

The infusion rates, this gets a little bit confusing, so I left it that way, although I really don’t like seeing it that way with two forward slashes. When we see a fraction, we usually we’re used to seeing a numerator over denominator, but here we have a numerator over a denominator and then another four slash. It just makes it a little confusing, but really at 0.6 mL over kilograms and then hours is also a denominator, so those are both on the bottom and we’ll see how that works when we’re doing our conversions.

How about what we have are three times and then when I say times I mean that quite literally. And let me get my pointer out here. I mean 30 minutes, 30 minutes, 30 minutes, but then an unknown and that’ll be kind of the twist at the end here that makes it a little bit tougher. But what is the total infusion duration of the immunoglobulin if it is infused at the prescribed rate? Well, we know it’s 30 plus 30 plus 30 plus something and we want it to the whole minute, so that’ll also be part of our conversion.

But the first thing to do I think is just say all right well I know eventually I’m going to have to know how many mLs I’m infusing total and I don’t really have that set up right now so let’s go look at that. All right so I have a 24 kilogram seven-year-old child and 0.5 grams per one kilogram. 100 mL per 10 grams equals the mLs. And I mentioned again I prefer to go right to left so if I see mLs I need a conversion factor that has mLs. Well this one didn’t have mLs but this one does so I put the 100 mLs over 10 grams and then I need to get rid of this gram because the gram is not over here so I see 0.5 grams over kilograms and I don’t see kilograms over here so I need to get rid of it and I get rid of 24 kilograms so then we cross out diagonally our units. I’ll get rid of the kilograms, get rid of the grams and we’re left with the mLs. So the total infusion will be 120 mLs.

Okay so that’s a nice number to work with and we’ll see we’re going to be able to figure out the infusion quantities for the first three but we’re going to need this 120 for our fourth infusion quantity. So there are two ways you could do this. And I mentioned this long way versus short way. The short way is to recognize that you’re going from 0.6 to 1.2 to 2.4 and you’re really doubling and then doubling again. Okay so you could really just put it over here and go 0.6 plus 1.2 plus 2.4 is going to end up at 4.2.

Or you can go through each of them and say okay well this one’s going to be 7.2 mLs and this one would be 14.4 and this would be 28.8 all together though we end up with the same product that we’re gonna or sum that we’re going to have 50.4 mLs.

So again if we have mLs as something that I’m looking for I need to have my conversion factor of mLs over kilograms per hour and as I mentioned we have that strange denominator one on the bottom so we need to multiply by kilograms and by hours because there’s no hours over here in the answer.

Okay so we can do that three times. I can get this 50.4 so if we’ve used 50.4 so far we know the total is 120 from the last equation that we did then the infusion quantity for the fourth segment is 120 mL minus 50.4 or 69.6 mLs. But unfortunately that’s not what the question asked. The question wanted to know what’s the total infusion duration. So we have that one of the unknowns known now now that we’ve calculated the 69.6 mLs and we can put plug that in.

So instead of having the hours here where we knew it was 0.5 of an hour or 30 minutes we know the answer we know it’s 69.6 mLs is the total amount so what we do is we do a little bit of rearranging here and we see that we’re going to have to move the 24 over so 1 over 24 when you move it from the left to the right and then again we have to move the 4 under the kilograms per hour and then when we do this calculation eventually we come up with 0.725 hours.

So I know you could just do 0.725 times 60 but I still like to do the entire thing to make sure that I’ve got the right factors so 0.725 hours times 60 minutes over one hour makes 43.5 minutes. So we already had our 90 at the very beginning of the question, we just need to add our 43.5 minutes to get 133.5 rounded to the nearest whole minute as per the question or 134 minutes.

So just one kind of caveat that if you’re filling in answers it sounds like you would want to go through the entire test and make sure that every answer is done properly here because you could have just left it at 133.5 and then gone on to the next but I want to make sure that we’re attentive to the actual question.

Thanks for listening to the Memorizing Pharmacology podcast. You can find episodes, cheat sheets, and more at memorizingfarm.com. Again, you can sign up for the email list at memorizingfarm.com to get your free suffixes cheat sheet or find our mobile-friendly self-paced online pharmacology review course at residency.teachable.com/p/mobile. Thanks again for listening.

Like to learn more?

Find my book here: https://geni.us/iA22iZ

or here: https://www.audible.com/pd/B01FSR7HLE/?source_code=AUDFPWS0223189MWT-BK-ACX0-059486&ref=acx_bty_BK_ACX0_059486_rh_us

and subscribe to YouTube Channel TonyPharmD here: https://www.youtube.com/c/tonypharmd

Here is the Link to my Pharmacy Residency Courses:  residency.teachable.com