RSS

Paramedic Math Fluid Administration

Occasionally, you may be given an order to administer a certain number of  milliliters of fluid over a certain period of time.  So let’s learn how to how to calculate the drip rate of our IV so we are giving the patient the amount of fluid we are supposed to be giving.

This calculation applies when we are running fluids alone or when we set up something like an Amiodarone drip where we are running the entire contents of our bag in 10 minutes.

So how do we calculate the desired drip rate on our IV to achieve administering the proper amount of fluid in the proper amount of time?

 

DD/T X gtt/1 ml

Fluid administration formula to calculate drip rates

In this formula DD = the amount of fluid we need to infuse, T = the amount of time we have to infuse it in, gtt = the number of drips in one ml of fluid (found on the label for  your administration set). Most resources I have seen use a V in this formula for the VOLUME to be infused… however since we already have a V defined in our variables, I am going to stuck with DD, after all fluids ARE medications and what are using is the desired dose of fluid over a length of time.

As I said in the dosage calculations I recommend you use the block of variables and plug them all in whether or not you are going to need them so you get a feel for finding the values in the orders and plugging them into the appropriate place in the formula. I also recommend until you have the formula down cold that you begin your solution by writing out the formula, this will reinforce your learning it the more you do it.

With me?

Good, let’s take a look at a few of these type of orders and how we go about solving them.

 

Administer 100 ml normal saline to a 150 pound male patient over the next 25 minutes. You have a 15 gtt set.

 

  • DD – 100 ml
  • C – N/A
  • V – N/A
  • gtt – 15 gtt
  • T – 25 minutes
  • WT – 150 lb (not used for this calc)

Fluid administration formula : DD/T  X  gtt/1 ml

  • plug in the variables : 100 ml/25 min  X 15 gtt / 1 ml
  • cancel like terms : 100 ml/25 min  X 15 gtt / 1 ml
  • reduce        =       4/1 min X 15 gtt/1
  • multiply       =            60 gtt/1 min
  • divide         =             60 gtt/min

 

In this case we would set our drip rate at 60 gtt(drops) per min or one drop per second

See I told you at the beginning these are confusing at first glance, but if you break them down and stay organized nothing you can’t handle.

Let’s try another one – this time without the color coding to help you through.

 

Medic three, this is trauma center doc with a med order – administer 1000 ml of ringers lactate over the next 30 minutes please. base out.From your call in report the base doc knows that your patient weighs 100 lb. You reach into the IV cabinet and grab a macro set (10 gtt/ml)

 

  • DD – 1000 ml
  • C –   N/A
  • V –   N/A
  • gtt – 10 gtt
  • T -30 Minutes
  • WT – 100 lb (not used)
Fluid administration formula : DD/T  X  gtt/1 ml
  • plug in the variables : 1000 ml/30 min  X 10 gtt / 1 ml
  • cancel like terms : 1000 ml/30 min  X 10 gtt / 1 ml
  • reduce        =       1000/30 min X 10 gtt/1
  • multiply       =            1000 gtt/3 min
  • divide         =            333 gtt/min (rounded down)

In this case we would set our drip rate at 333 gtt(drops) per min .

 

 

Yes I realize 5 drops a second is faster then we can count (I didn’t say it was practical) but the math IS right.

So how does the order being weight based affect this formula – see how good you are getting at this – that’s correct – it DOES NOT change the formula.

It does however require you to calculate the DD before you can work the equation

Let’s give one of those a shot before we move on to the grand daddy of the equations…

 

Administer 20ml/kg normal saline to your 170 lb male patient using a 10 drop set over he next hour
  • DD – 20ml/kg
  • C – N/A
  • V – N/A
  • gtt – 10 gtt
  • T – 60 minutes
  • WT – 170 lb

To get our DD for the equation we must first do a little math

  • convert from lbs to kg (multiply by 0.453 or divide by 2.2)
    • 170  X  0.453  = 77.01 kg
    • round down – 77.01 kg = 77 kg
  • multiply the patients weight in kg by the amount ordered
    • 77  x  20 = 1540 ml
  • this value becomes our DD for the equation
Fluid administration formula : DD/T  X  gtt/1 m

  • plug in the variables : 1540 ml/60 min  X 10 gtt / 1 ml
  • cancel like terms : 1540 ml/60 min  X 10 gtt / 1 ml
  • reduce        =       1540/60 min X 10 gtt/1
  • multiply       =           1540  gtt/6 min
  • divide         =             257 gtt/min (rounded up)

In this case we would set our drip rate at 257 gtt(drops) per min

 

 

Feeling pretty good about the fluid rates and the dosage calculations?

Good because the next step is to combine to two so we can arrive at the formula for the oft cursed dopamine drip. Once that chill finishes going down your spine feel free to keep reading.

Relax… you’ve got this and I’ll walk you through it nice and easy like.

Drug Drip Calculations

 

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>