The Savvy VetTech

New call-to-action

Let's Practice Calculating A Constant Rate Infusion (CRI)

by Lori Hehn - Sep 15, 2016 8:00:00 AM
Find me on:


Let's work through the math on calculating constant rate infusion word problem!

An 11-pound Yorkshire Terrier has been prescribed a 2 mg/kg/day constant rate infusion of metoclopramide.  The metoclopramide is to be added to the intravenous fluids.  If the concentration of metoclopramide is 5 mg/ml and the Yorkie’s fluid rate of Lactated Ringer's (LRS) is 20 ml/hr, how many milliliters of metoclopramide should be added to a 500 ml bag of intravenous fluids?


New call-to-action

First convert pounds into kilograms by dividing pounds by 2.2 (there are 2.2 pounds per kilogram):

11 pounds/ 2.2 pounds per kg (pounds cancel out) = 5 kg

Now take the kg and multiply by the dose:

5kg X 2 mg/kg/day (kg cancel out) = 10 mg/day

Now divide by the number of hours in a day (24) to get the per hour rate:

10 mg/day / 24 hours/day (days cancel out) = 0.4 mg/hour

Next divide by the concentration of metoclopramide:

0.4 mg/hr / 5mg/mL (mg cancel out) = 0.08 mL metoclopramide/hour

Now find out how many hours this bag will last by taking the amount of fluids in the bag divided by this dog’s current fluid rate:

500 mL/bag/ 20 ml/hr = 25 hours of IV fluids/bag (at this current rate)

Lastly, take the number of hours this bag will last and multiply by the mL/hour of metoclopramide:

25 hours/bag X 0.08 mL metoclopramide/hour (hours cancel out) = 2 mL of metoclopramide / 500 mL bag

To keep it completely accurate, you would remove 2 mL of LRS fluids from the bag, and add back in your 2 mL of metoclopramide.

Want more practice? Check out this Link on Constant Rate Infusions via DVM360!

The Top 15 Tips and Tricks for Studying for the VTNE

Studying for the VTNEYou're of course going to need to study a ton to nail the test, but there are a lot of tips and tricks that will help you make the most of your study time and we've packaged those up in a free guide.

Some of the Top 15 Tips include:

    • Familiarize Yourself with the Test Format
    • Tackle the Weak Subjects Early
    • Start Sooner and Ease Into It
    • ...and 12 more!

Download Now!

in Calculations 11 Comments

About Lori Hehn

Lori Hehn is a practicing veterinarian and a contributor and content manager with XPrep Learning Solutions. She has a drive for continual learning and enjoys interacting with veterinary and vet tech students. She also writes veterinary learning books for children.

Popular Posts

Posts by Topic

see all