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Paramedic Math Good Drug Drip Calculations

Take a deep breath… I know these calculations are the ones you’ve heard people curse and grumble about. There’s a bit of math to them especially when we get to the dopamine drips… while it’s a bit of calculating and converting, the good news is – IT IS NOT ANY MORE DIFFICULT THEN WHAT YOU HAVE ALREADY DONE..

Stay organized and break each drip calculation down into steps and you will get through it – I promise it isn’t that bad after doing it a few times.

These calculations are a combination of the two previously learned formulas – which is why I didn’t want to change the V variable in the last set of equations.

Enough chatting about it – Let’s get to the formula for these equations :

 

V/C X DD/M X gtt/1 ml

The formula used to calculate dopamine drips and other medication drip rates.

 

WOW that’s a bunch of variables for one equation isn’t it? It looks scary at first, but there is NOTHING here we haven’t already done with the other two formulas.

V= volume, C = Concentration, DD = desired dose, M = minutes (unless specified this is 1), gtt = drip rate of the admin set, and the 1 ml is constant in all the equations.

You will quickly see why I have been saying all along to write all the variables down – we will use all of them by the time we are done with these.

Staying organized with your calculations will get more important as we go down the page, so if you haven’t been working that way all along this would be a good time to start.

Let’s start with a non dopamine drip (there’s another step to the dope drip) just to get your feet wet.

Administer 10 mg/min of a medication the medication comes 5 g of medication in 5 ml, you have a liter of normal saline and a 60 drop set to your 225 lb patient.

 
Variables list

  • DD – 10 mg
  • V – 1 Liter
  • C -5 g
  • T -1 minute
  • gtt – 60 gtt
  • WT – 225
 Drip rate calculation formula : V/C  X  DD/T  X gtt/1 ml

  • plug in the variables = 1 L /5 g  X 10 mg/ 1 min  X 60 gtt/1 ml
  • convert to like variables = 1000 ml/5000 mg X 10 mg/ 1 min  x 60 gtt/ 1 ml
  • eliminate like labels 1000 ml/5000 mgX 10 mg/1 min X 60 gtt /1 ml
  • reduce = 1/5  X 10/1 min x 60 gtt/ 1
  • multiply = 600 gtt/ 5 min
  • divide = 120 gtt/min
For this particular order we would need to set our drip rate at 120 gtt/min

That wasn’t too bad now was it? Let’s move a little closer to the dope drip with the next one to get you comfortable working the formula.

Administer 4 mcg/min of a medication to your 143 lb patient, the medication comes 2 mg in a 5 ml vial, you have a 500 ml bag of saline and a 60 drop set.
Variables list

  • DD – 4 mcg
  • V – 500 ml
  • C – 2 mg
  • T – 1 minute
  • gtt – 60 gtt
  • WT – 143 lb
 Formula : V/C  X  DD/T  X  gtt/ 1 ml

  • plug in variables  = 500 ml/2 mg  X  4 mcg/1 min  X  60 gtt/1 ml
  • convert to like variables = 500 ml/ 2000 mcg  X 4 mcg /1 min  X 60 gtt/ 1 ml
  • eliminate like labels = 500/2000 X 4/ 1 min  X 60 gtt/1
  • reduce = 5/2  X  4/1 min  X 6 gtt/ 1
  • multiply = 120 gtt/ 2 min
  • divide = 60 gtt/min
For this order we will set our drip rate at 60 gtt/min

We’re gonna kick it up one more notch here and practice a few of them before we get to the dreaded dope drip…

Now we are going to give a weight based mcg dose… so we will have convert from pounds to kg and convert our concentration to mcg…

 Administer 10 mcg/kg/min to your 196 lb patient. Your drug dose is 400 mg, you have a 250 ml bag and a 60 gtt set.
Variables list

  • DD – 10mcg/kg
  • V – 250 ml
  • C – 400 mg
  • T – 1 minute
  • gtt – 60 gtt
  • WT – 196 lb
  1. Convert from lbs to kg – 196 X .0453 = 88.788 kg
  2. round to 89 kg
  3. multiply DD 10 mcg/ 89 kg = 890 mcg
 drip rate formula: V/C  X  DD/T  X  gtt/1ml

  • plug in variables : 250 ml/400 mg  X  890 mcg/1 min  X   60gtt/1ml
  • convert variables: 250 ml/400000 mcg  X  890 mcg/ 1 min  X 60gtt/1 ml
  • eliminate like labels: 250/400000 X 890/1 min X 60gtt/1 ml
  • reduce: 1/1600 X 890/1 min X 60 gtt/1 ml
  • Multiply: 53400 gtt/1600 min
  • divide : 33.375 gtt/min
To properly administer this medication we need to set our drip rate to 33 gtt/min

Let’s do a couple more like that to get the hang of it

Administer 7 mcg/kg/min to your 163 lb male patient. Your medication comes 400 mg in a vial. you have a 250 cc bag and a 60 gtt set.
Variables list

  • DD -7mcg/kg
  • V – 250 ml
  • C – 400 mg
  • T – 1 min
  • gtt – 60 gtt
  • WT – 163 lbs.
  1. convert 163 lbs to kg 163 X 0.453 = 73.839 kg
  2. round to closest whole number = 74 kg
  3. multiply 7 mcg by 74 kg = 518 mcg
 Drip rate calculation formula : V/C  X  DD/ T  X  gtt/ 1 ml

  • plug in variables = 250 ml/400 mg X 518 mcg/1 min x 60 gtt /1 ml
  • convert variables = 250 ml/400000 mcg x 518 mcg/1 min x 60 gtt/1 ml
  • eliminate like labels = 250/400000 x 518/1 min x 60 gtt/1 ml
  • reduce = 1/1600 x 518/1 min x 60 gtt/ 1
  • multiply = 31080 gtt/ 1600 min
  • divide = 19.425 gtt/min
 To properly administer this medication we need to set our drip rate 19 gtt/min

Let’s do just one more

administer 12mcg/kg/min to your 138 lb female patient, Your medication comes 400 mg in a vial, you have a 250 cc bag and a 60  gtt set.
Variables list

  • DD – 12 mcg/kg
  • V -250 ml
  • C – 400 mg
  • T – 1 min
  • gtt – 60 gtt
  • WT – 138 lb
  1. convert 138 lbs to kg  – 138 x 0.453 = 62.514 kg
  2. round to nearest whole number = 63 kg
  3. find desired dose = 63 kg X 12 mcg = 756 mcg
 Drip rate calculation formula : v/c  X  DD/ T  X  gtt/ 1 ml

  • plug in the variables – 250 ml/400 mg  x 756 mcg/1 min X 60 gtt/ 1 ml
  • convert to like variables – 250 ml/400000 mcg X 756 mcg/ 1 min X 60 gtt/1 ml
  • eliminate like labels – 250/400000 x 756/ 1 min x 60 gtt/1 ml
  • reduce = 1/1600  x 756/1 min  x  60 gtt/1 ml
  • multiply = 45360 gtt/ 1600 min
  • divide = 28.35 gtt/min
To properly administer this medication we need to set our drip rate at 28gtt/min

 

Alright, you’ve heard about them, you’ve wondered why they are so hated among your paramedic partners, let’s talk about those  dopamine drips.

What makes a dope drip more difficult to figure is it is a weight based dose, and the dosage is in mcg so there are conversions and calculations to do before you can actually work the equation. We just practiced that very thing… in fact those last three equations were actual dopamine drip equations. I figured if you’ve heard as much about them as I had before I learned them, you were a little intimidated by them. This way we could work them out without you getting all psyched by knowing that’s what they were. Feel better?

You struggled through learning the equations, and solving them along with me. I think it’s time I give you a few short cuts. I will say that these short cuts will work in the field… they are tried and true, DO NOT use them to solve a national registry exam calculation as the ratio of medication to drug may not be an actual ratio we would use in the field, it is therefore vital to know the proper way to solve these the long way for now.

On to the short cuts…

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  1. CCC

    October 21, 2011 at 17:29

    I’ve always used what I learned a long time ago.

    Dosage x Weight (in kg) x 60 minutes / Concentration

    Perhaps that’s what you said up there. I just got confused and scared of the math. (Plus, my service REQUIRES us to use a web-based calcuation system that gets recorded in the ePCR.)

    Reply