Drug Calculations

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Drug Calculations

• 1 hour CEU
• By Kevin Fabian, NREMT-P
• Berkeley County EMS,
• S.C.

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Introduction

• Ever hear someone say in high school Ill never
  use algebra again? Well, if youre a paramedic
  that calculates drug infusions, then you use at
  least a little algebra. However, the one thing
  it is not is ROCKET SCIENCE!!

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• There are many theories, formulas, and shortcuts
  to finding the right answer for drug infusions.
  In fact, people so hate to memorize an algebraic
  formula that they memorize twice as many
  shortcuts. My advice is three-fold.
• 1) Do what works for you
• 2) Keep it simple
• 3) If youre having trouble, just stick with one
  
• method and master it.

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• I will present the formula here that I like to
  use. As I said before, if you have a method that
  works for you, then use that. As long as we both
  come up with the same (correct) answer, the
  patient will survive.

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A formula

• Heres the formula I like to use
• Desired dose X Weight X Drop set
• ---------------------------------------- drops
• Drug (on hand) / Fluid
  per min.

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This formula is derived directly from the Dose on
Hand method taught in many paramedic textbooks.
But, instead of this being a 5 or 6 step process,
it is a 5 part formula. Memorize these 5 parts,
and youve got it !!!
1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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• To explain the parts
• Desired Dose the dose that is ordered such as
  2 mg/min, 5 mcg/min, 7 mcg/kg/min, etc.
• - Write ONLY the number that represents the
  dose you want. If the dose you want is 7
  mcg/kg/min, then just write 7.
• Hint mcg micrograms

1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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To explain the parts 2) Weight Write the
patients weight in kg. Kg is the unit of weight
that pretty much all drugs these days are ordered
by, so get used to it. If you are provided a
weight in pounds, then divide pounds by 2.2 to
get kg. - If the drug is not weight
dependent, then leave this number out of the
formula. Its that easy! Hint kg kilograms
1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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To explain the parts 3) Drop set Write the
SIZE of the drop set you are using. If its a 60
drop set, write 60. - This number is what
makes the entire formula equal a drops per minute
value. In other words, if you leave this number
out, such as when you use an I.V. pump, then the
entire formula equals ccs per minute. Hint cc
ml
1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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To explain the parts 4) Drug on hand This is
what youre taking out of the box. Look on the
vial, pre-filled syringe, etc. and see how much
drug youre holding. It may be 1 gram of
lidocaine, 200 mg of dopamine, etc. It would be
best if you would make sure, at this point, that
your drug on hand matches the UNIT of your
desired dose. Ill explain how 2 slides from
now. Hint 1 gram 1000 mg 1 mg 1000
mcg
1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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To explain the parts 5) Fluid This is what
youre mixing your drug into. It may be a 500cc
bag of D5W, a 250cc bag of normal saline, a 50cc
syringe, or whatever you choose. Write the
volume.
1) Desired dose X 2) Weight X 3) Drop
set ----------------------------------------------
------------------- drops
4) Drug (on hand) / 5) Fluid
per min.
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To make your drug on hand match your desired
dose If your desired dose 4 mg, and your drug
on hand 1 gram, just add 000 after the 1,
and youve made your conversion. This is because
1 gram 1000 mg. If you do this in reverse
order, 1000 mg to 1 gram, it becomes an issue of
a decimal point. Dont get yourself confused
with that if its not necessary.
Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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Another example If your desired dose 4 mcg,
and your drug on hand 1 mg, just add 000
after the 1, and youve made your conversion.
This is because 1 mg 1000 mcg. Just remember 1
gram 1000 mg 1 mg 1000 mcg

Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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Lets try one!! You are ordered to give a
Lidocaine infusion at 2 mg per minute. You have
a 60 drop set, 1 gram of Lidocaine, and a 250cc
bag of D5W. How many drops per minute? Plug the
numbers into the formula below 2 X 60 (leave out
the weight for Lidocaine) 120 ------------------
---------------------------- 1000 mg
divided by 250 4
120 divided by 4 30 drops per minute.
Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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Heres another You are ordered to give a
Procainamide infusion at 4 mg per minute. You
have a 60 drop set, 2 grams of Procainamide, and
a 500cc bag of D5W. How many drops per minute?
Plug the numbers into the formula below 4 X 60
(leave out the weight for Procainamide)
240 ----------------------------------------------
2000 mg divided by 500cc
4 240 divided by 4 60 drops
per minute.
Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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Heres another You are ordered to give a
Dopamine infusion at 5 mcg/kg/per minute. You
have a 60 drop set, 200 mg of Dopamine, and a
500cc bag of D5W. Your patient weighs 90 kg.
How many drops per minute? Plug the numbers into
the formula below 4 X 90 X60
21600 -------------------
--------------------------- 200000 mcg
divided by 500cc 800 21600 div.
by 800 27 drops per min.
Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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You are ordered to give an Epinephrine infusion
at 5 mcg/per minute. You have a 60 drop set, 1
mg of Epinephrine, and a 250cc bag of D5W. How
many drops per minute? Plug the numbers into the
formula below 5 X (no weight needed) X60
300 ------------------------------------
---------- 1 mg divided by 250cc
4 300 div. by 4 75 drops per
min.
Desired dose X Weight X Drop
set ----------------------------------------------
------------------- drops
Drug (on hand) / Fluid
per min.
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You are ordered to give an Epinephrine infusion
at 8 mcg/per minute THROUGH A SYRINGE PUMP.
You have a 60 drop set, 1 mg of Epinephrine, and
a 250cc bag of D5W. How many drops per minute?
Plug the numbers into the formula below THE
SYRINGE PUMP WANTS CCS PER HOUR. Remember, with
some pumps, there is no need to calculate a drop
set factor 5 X (no weight needed) X (no drop
set needed) 5 ----------------------------------
---------------------- 1 mg divided by 250cc
4 5 div. by
4 1.25 CCs per min. 1.25 ccs per min. times
60 min 75 cc/hr
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Now, prepare to work out some problems on your
own. Take out a sheet of paper. After the first
few problems, you will be timed. You will have
30 seconds to achieve the correct answer, to
within 4 drops per minute, or 0.1 cc per minute.
(If you are 0.1 high, you will give an extra 6cc
per hour).