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# Medical Math – Metoclopramide CRI

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Megan Brashear, CVT, VTS (ECC), walks you through how to calculate a metoclopramide CRI for any sized patient when adding the drug to their already running IV fluids. This calculation is used for adding any drug to fluids that are being administered at a set rate.## Sidebar Bookmark Button

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Just a quick question, forgive me if it is common sense right now!

When do we know to use the "low end" or the "high end", does it base off of weight?

Hi Cynthia, don't apologize for questions! :) The low or high end of the dose is a decision made by the veterinarian and will be their preference due to their experience with the drug. They may want to start at the low end knowing it gives them room to increase the dose if the patient is not responding they way we would like, but they will have you figure out the amount of drug to add based on the dose that they give you.

It's typical at out hospital that the Dr. Will increase IVF during sx. Then lower to maintenance after. If you are using a CRI, how does that play into pain management?

Cassidy, if the CRI is included in the maintenance IV fluids then an increase in rate during surgery will increase the amount of drug given. As the technician, it is important to know how many mg/kg/ml of the drug are in the bag of fluids so you know how much the patient is receiving during increased fluid rates. At DoveLewis, we will often have a clean bag of IV fluids used just for surgery that we can use to bolus and make up for the higher surgical rate of fluids.

Question: When you back track to check your answer and you multiply your final answer by 0.15 when its 15mls/hr.....how do you get the 0.15????

Good question Caroline. In order to double check your answer you multiply the dose you are adding (33.4mg/L) by the rate (15mL/hr). Before you multiply these things together you need to change your units so that they are the same. In the example above, Megan is converting 15mL/hr to L/hr. There are 1000mL in one liter, so you divide 15mL/1000mL= 0.015L/min. Now that you know that, you can multiply 33.4mg/L * 0.015L/hr = 0.5mg/hr. You then take 0.5mg/hr*24hr= 12mg/day, which confirms our answer supports our desired amount.

Question regarding adjusting a reglan cri? Often times we will calculate out 2mg/kg/day in a liter of fluids and at some point the DOD will have us decrease the rate hours later. How do we adjust the reglan that's already in the bag based on the new fluid rate? I.e. our initial dose was 2mg/kg/day 15kg dog rate at 44ml/hr in 1 liter, now we have 750mls left in the bag and the doctor wants the rate dropped to 30ml/hr. Thank you!

Hi Brittany,

That is a great question! If you are finding you are making frequent changes to your CRI's using a burette is a great way to make changes to fluids as you can start from scratch and not waste a large amount. Or smaller bags for CRI's. You could also use a Y set and make a separate CRI to make up the difference as Reglan is compatible with all fluids.

Here is how you would calculate the adjustment for the fluid rate change. I hope this is easy to follow as writing it out is a little more difficult for me vs being able to explain it to you.

*Please note I did round when appropriate and the outcome is within a reasonable amount.*

You would start by calculating the original concentration of the bag where it is 2mg/kg/day for a patient that is 15kg and the rate is 44ml/hr in a new liter.

Remember: Reglan’s concentration is 5mg/ml

My calculations are as follows: 2mg/kg/day for a 15kg pet = 30mg/day. There is 24hrs in a day so 24hr x 44ml/hr= 1,056ml/day

Then your concentration per ml: 30mg/1,056ml/day=0.028mg/ml of Reglan

You would then figure out the concentration for one Liter: 0.028mg/ml x 1,000= 28.4mg of Reglan in one Liter. This is what you will add to the bag in order to deliver 30mg/day to your 15kg patient at 44ml/hr.

When the doctor wants to lower the rate to 30ml/hr but continue to deliver the same 30mg/day you will need to figure out the difference and what to add to make up that difference. You have 750mls remaining in the bag so how many mgs of Reglan are remaining in that bag? 0.028mg/ml x 750= 21mg of Reglan in the remaining 750mls

So calculate how many mgs need to be in the bag in order to deliver 30mg/day at the new rate of 30ml/hr

24hrs x 30ml/hr= 720mls/day

30mg/720mls=0.042mg/ml is the concentration you need.

Figure out the difference in the concentrations: 0.042mg/ml – 0.028mg/ml= 0.014mg/ml

Then take the difference in mg/ml and multiply it by the remaining amount of fluids: 0.014mg/ml x 750mls= 10.5mg

10.5mgs of Reglan needs to be added to the remaining 750mls so that the 30mg/day is still delivered at a lower fluid rate.

Make sure to agitate the bag after you add the Reglan and run the amount of fluid the line holds though the fluid set so that you are delivering that new concentration. Also make sure you edit the concentration on your fluid bag too.

I hope this makes sense and helps! Let me know if you have any other questions.

I just have a question. On the worksheet, question 2, it says 4mcg * 60. Where did you get the 60 from?

Hi Kristen,

We want to find how many mg of Dopamine to add to the 100mLs of NaCl so that the concentration is 1mcg/kg/min but the rate will be 1mL/hr so we need to change the minutes unit to an hour. There are 60 minutes in an hour so multiple 4mcg * 60 mins = 240mcg/hr

I hope that makes sense? I wanted to try to explain it vs just saying there are 60 minutes in an hour haha.

Hope that helps!