I'm soooo lost on my med math homework! Can anyone help me?

loriangel14, RN · May 1, 2013

OK so the pt weighs 70kg and you need to give 18 units per kg/hr. You would multiply 70 by 18 giving you 1260. So the patient would be getting 1260 units per hour.

I use the doc over stock formula. Doc ( what is ordered by the doctor) is 1260 units. Stock ( what you have in stock) is 25000 units. So 1260 divided by 25000 is 0.0504. Then you multiply by the vehicle ( the 500 mls in this case). 0.0504 is 25.2. Rounded off your answer would be 25ml/hr.

ShyeoftheTiger · May 1, 2013

Ok, I'm a student nurse enrolled in the LVN program and I'm about to start my second semester. I have never been a brainaic at math and this med math is KILLING me. I've been lucky enough to not flunk out (so far... it's been a nightmare!) but I could REALLY use the extra help with things like DF's, and da equations.
The problem reads: Ordered: Heparin 18 units per kg per hr in a continuous infusion. Available: Heparin 25,000 units in a 500 mL D5W. Patient's weight: 70kg.
a. How many units per hr are ordered? :
DA equation:
b. The nurse will set the flow rate at how many mL per hr?:
DA equation:
I'm soooooo lost! Can anyone help me?

*I am not a nursing student yet*

Here's my guess

A) 1,260 units per hour (70kg x 18 units = 1,260 units)

B) 25.2 mL per hour (25,000u/500mL = 1u/50mL; 1260u/50mL = 25.2mL/hour)

I could be way off...

ShyeoftheTiger · May 1, 2013

OK so the pt weighs 70kg and you need to give 18 units per kg/hr. You would multiply 70 by 18 giving you 1260. So the patient would be getting 1260 units per hour.
I use the doc over stock formula. Doc ( what is ordered by the doctor) is 1260 units. Stock ( what you have in stock) is 25000 units. So 1260 divided by 25000 is 0.0504. Then you multiply by the vehicle ( the 500 mls in this case). 0.0504 is 25.2. Rounded off your answer would be 25ml/hr.

Woo! I was close!

loriangel14, RN · May 1, 2013

You were right, you just need to round off.

Esme12, ASN, BSN, RN · May 1, 2013

Dimensional analysis.....http://www.davesems.com/files/drug_dose_calculations.pdf

and DosageHelp.com - Helping Nursing Students Learn Dosage Calculations

Will help as well...goodluck!

SopranoKris, MSN, RN, NP · May 2, 2013

I had Pharmacology last semester and I HIGHLY recommend "Math Attack: Strategies for Winning the Pharmacology Math Battle" by Karen Champion. She explains all dosaging problems in an easy-to-understand method. You pick the one that works best for you. It helped me ace my dosaging math tests in Pharm. Our program requires a 90% or better on all math quizzes or you fail the entire class! Stressful, but it's necessary. You don't want to make a math error in the real world :)

Shorty11, BSN, RN · May 4, 2013

I solve these similar to the way loriangel does. I was taught "desired" divided by "on-hand". Then multiplied by the "volume." I'm really not a fan of dimensional analysis (personal preference), but if it works for you, great! Dimensional analysis is a great way to keep your units straight and to have "everything" in one uniform equation. I prefer to break things down into a couple of smaller equations as opposed to dimensional analysis (again, just a personal preference). If you do it this way, key is to make sure to keep track of your units as you go along. I learned dosage calc from "Calculate with Confidence" by Morris (ISBN 978-032-305-6298). The book provides many examples of different ways to solve different types of problems... you can practice each way of solving and figure out which way works best for you. Includes lots of practice problems. Granted, it probably isn't the best book out there on the subject, but I have made an A on every dosage calc test I have had so far.

mistybeck · May 5, 2013

I find dimentional analysis to be the easiest way to work out dosage calculations. It lines up really nice, and you just have to multiply the fractions. If you follow these 3 rules for your calculations, it's simple. Step 1: Start out with what you're looking for (just put the units of measurement first without any numbers to get your thoughts straight). Step 2: Your next numerator has to have the same unit of measurement as your previous denominator (this is so you can cancel them out). Step 3: When you are left with only the units of measurement you are looking for, you are done...just do the math straight across.The problem reads: Ordered: Heparin 18 units per kg per hr in a continuous infusion. Available: Heparin 25,000 units in a 500 mL D5W. Patient's weight: 70kg.a. How many units per hr are ordered? U/ hr = 18 U/ kg/hr X 70 kg/ 1 (I use a 1 as a filler when nothing else goes there. It's not really needed in this case, but in a more complicated problem, it helps) = 1260/ 1 = 1260 U/ hr b. The nurse will set the flow rate at how many mL per hr? mL/ hr = 500 mL/ 25,000 U X 1260 U/ hr = 630,000/ 25,000 = 25.2 --> 25 mL/ hr I had this typed in Word so I could should the fractions better and how you cancel out the units of measurement, but I couldn't figure out how to attach it lol. Anyway, I hope this makes sense.