Download Medication Calculations - Centegra Health System

McHenry Western Lake County EMS System
Optional CE for Paramedics, EMT-B and PHRN’s
Calculating Medications
Optional #3 - 2017
There are different ways for pre-hospital care to administer medications. Medications can be
administered by Intra-Nasal (IN), Intra-Muscular (IM), Orally (PO), Intra-Venous (IV), Intraosseus (IO)
Inter Rectal (IR) or by Hand Held Nebulizer (HHN or Neb). Since the body will absorb the medication
differently through each of these routes, the concentrations of the medications may be different. The
other important consideration is that the medication dosage may be different than the actual amount of
fluid that will be administered. Not all medications are given in a 1:1 medication to fluid ratio. It is very
important to know how to calculate, draw up and administer the right amount of medication in the right
amount of fluid. Where this is critical is in our pediatric patients. With the adult patient, we can
estimate a weight and “Ball Park” the dosage, but a pediatric patient is a lot less forgiving when too
much of a medication is given. Also, if we don’t give enough, we will not make the change that is
required.
Metric System
Pharmacology is based on the metric system. The metric system is based on powers of 10. To simplify
numbers with a lot of zeros, the metric system refers to milli- (1/1,000), centi- (1/100), deci- (1/10) and
will attach these references to what is being measured: grams (weight), liters (volume) and/or meters
(distance).
For example:
Since all the medications are setup in the metric system, we need to convert the patient’s weight into
grams. This is easily done by dividing the patient’s weight (in pounds) by 2.2. This will give the most
accurate weight in Kilograms (kg).
When a medication is given, the concentration of the medication is what is important. This can be in
grams (g) or milligrams (mg). The amount of fluid that holds the medication concentration is what will
be measured and given to the patient. This will be in milliliters (ml). Because these amounts are not
always the same, we have to make sure we are giving the proper amount of fluid for the proper amount
of medication.
Figuring out Medication Dosages and the Fluid amount
Vials and Preloads
There are 2 common methods to figure out medication dosages to fluid administration amounts. It is up
to you which one you follow, just practice, practice, and practice some more. It does not matter which
formula you use, but you will need to know Drug Order, Volume on Hand and Dosage on hand.
Medications can be packaged in vials that need to be drawn up (IM/IN) or preloads that have the
concentration already mixed (given IVP). With Preloaded medications, the calculations are done and
you only need to put the syringe together. In some of the SOPs we are giving the entire preload to the
patient. For a pediatric patient, we may only be giving a portion of that preload.
Epinephrine 1mg/1ml is supplied in a 1:1 ratio. So if you give 1 ml of fluid, then you will give 1 mg of
Epinephrine. If you give 0.3 ml of fluid, then you gave 0.3 mg of medication. That works when the
concentration is 1:1. With Epinephrine 1mg/10ml, we are giving a different fluid amount for the
concentration of the medication. 1 ml is now equal to 0.1 mg of Epinephrine. So if we need to give
0.3 mg of Epinephrine 1mg/10ml, we would give 3 ml of fluid.
Formula #1
When we get to pediatric dosages, we will administer a percentage of the vial based on the patient’s
weight. That is why it is important to covert the patient’s weight to kilograms (kg). If we want to give
Epinephrine 1mg/1ml IM (0.01 mg/kg) to a 33 pound patient we figure out the fluid amount with the
following formula:
Our First step is to convert our patient’s weight to kilograms.
33/2.2 = 15 kg
So we need to give 0.01 mg/kg x 15 kg = 0.15 mg of Epi 1ml/1mg
Since we know that this Epi is packaged 1mg/1ml we would give 0.15 ml of fluid.
Now let’s look at giving Atropine to a 48 lb. pediatric patient. Atropine is given 0.02 mg/kg for the
pediatric patient. (FYI, with pediatric dosages, we don’t exceed an adult dose. This applies to all
medications. For Atropine, the adult dose is 0.5 mg.) So for our patient, we would give:
48/2.2 = 22 kg
0.02 mg/kg x 22 kg = 0.44 mg of Atropine
Since Atropine is packaged 1 mg in 10 ml, we need to figure out how much fluid should be given to get
0.44 mg of Atropine. We can use the formula from above:
0.44 mg x 10 ml
1 mg
=
0.44 mg x 10 ml
1 mg
=
4.4 ml = 4.4 ml of fluid for 0.44 mg of Atropine
1
Formula #2 (with the same information….literally)
When we get to pediatric dosages, we will administer a percentage of the vial based on the patient’s
weight. That is why it is important to covert the patient’s weight to kilograms (kg). If we want to give
Epinephrine 1mg/1ml IM (0.01 mg/kg) to a 33 pound patient we figure out the fluid amount with the
following formula:
Drug Ordered
Volume to be
Delivered
x
Dosage on Hand
Volume on hand
Our First step is to convert our patient’s weight to kilograms.
33/2.2 = 15 kg
So we need to give 0.01 mg/kg x 15 kg = 0.15 mg of Epi 1ml/1mg
Since we know that this Epi is packaged 1mg/1ml we would give 0.15 ml of fluid.
Now let’s look at giving Atropine to a 48 lb. pediatric patient. Atropine is given 0.02 mg/kg for the
pediatric patient. (FYI, with pediatric dosages, we don’t exceed an adult dose. This applies to all
medications. For Atropine, the adult dose is 0.5 mg.) So for our patient, we would give:
48/2.2 = 22 kg
0.02 mg/kg x 22 kg = 0.44 mg of Atropine
Since Atropine is packaged 1 mg in 10 ml, we need to figure out how much fluid should be given to get
0.44 mg of Atropine. We can use the formula from above:
0.44 mg
X
1mg
= 0.44 mg x 10 ml
10 ml =
X x 1 mg
=
=
4.4 ml = 4.4 ml of fluid for 0.44 mg of Atropine
1
Either formula will give you the same answer.
Drip Rates
Not all medications are packaged in preloaded syringes. Some medications are administered as an IV
Bag with the medication given as a drip, not a one-time push (IVP/IM/IN). With most IV bag
administrations, you will need to figure out a drip rate for the administration over a fixed period of time.
An example is Amiodarone for a Wide Complex Tachycardia with a Pulse. This medication can be given
in 150mg/7ml slow (IVP/IO) or 150mg/50ml (IVBP). Both administrations are over 10 minutes. To setup
the drip rate for the IV, you need to know the following things: 1) volume to be infused (ml), period of
time for the administration (minutes) and the drops per minute that the IV tubing can administer (or
Infusion set - 60 gtts/ml, 15gtts/ml or 10gtts/ml). We know that the drug dose is 150mg.
The formula to figure out the drip rate is:
Let’s plug Amiodarone into the formula:
50 ml x 60 gtts/ml =
10 minutes
50 ml x 60 gtts/ml =
10 minutes
50 x 60 gtts = 3,000 gtts =
10 minutes
10 minutes
300 gtts/minute
With a micro set of IV Tubing (60 gtts/ml), we would administer 300 gtts/minute for 10 minutes.
50 ml x 15 gtts/ml =
10 minutes
50 ml x 15 gtts/ml =
10 minutes
50 x 15 gtts = 1,500 gtts =
10 minutes 10 minutes
75 gtts/minute
With a macro set of IV Tubing (15 gtts/ml), we would administer 75 gtts/minute for 10 minutes.
50 ml x 10 gtts/ml =
10 minutes
50 ml x 10 gtts/ml =
10 minutes
50 x 10 gtts = 500 gtts =
10 minutes
10 minutes
50 gtts/minute
With a macro set of IV Tubing (10 gtts/ml), we would administer 50 gtts/minute for 10 minutes.
IV Medications
For a medication that is prepackaged as an IV Bag (like Dopamine), we need to figure out a drip rate to
administer the desired amount of the medication. (For other medications, we may still need to figure
out the dosage by using the previous formulas.) The formula to do this combines both of the previous
formulas. For a Dopamine administration, we would always use a micro drip set (60gtts/ml).
The patient’s weight is 200 lbs. and we want to give 5mcg/kg/min.
The Dopamine package is 400mg/250 ml. We will need to figure out the mg per ml to put into the
formula.
Weight: 200/2.2 = 90.9 or 91 kg
mg per ml: 400/250 = 1.6 mg/ml but we need mcg, so 1600 mcg/min
5 mcg/kg/min x 91 kg x 60 gtts/ml = 5 mcg/kg/min x 91 kg x 60 gtts/ml = 5/min x 91 x 60 gtts =
1600 mcg/ml
1600 mcg/ml
1600
27,300 gtts/min =
1600
17.06 gtts/min or 17 gtts/min
For Dopamine, there is a quick “Field Calculation” to figure out the drip rate at 5mcg/kg/min. Take the
patient’s weight in pounds and drop the last digit. Subtract 2 from that number. That number becomes
the gtts/min that is needed. Because of rounding, the “Field Calculation” should get you within 1
gtts/min. For our patient above:
200 becomes 20
20 – 2 = 18 gtts/min
If the Dopamine dose changes to 10mcg/kg/min; you would double the 5mcg/kg/min answer. (or 36
gtts/min)
This has been a review of how to calculate medications and the fluid amounts that will be given to our
patient. Remember to document the medication dosage (mg) that was given, not the fluid amount.
Though there are easier ways to figure out the dosage for a patient (charts, apps, etc.), we may not
always have access to them. With practice, you’ll be able to go through these formulas quickly and be
able to use the charts/apps to verify your answer.
Reference used:
Bledsoe, Bryan E., Porter, Robert S., Cherry, Richard A., (2013). Paramedic Fundamentals. Paramedic
Care, Principles & Practice Vol. 2 (pp. 284-290).
McHenry Western Lake County EMS System
Optional CE for Paramedics, EMT-B and PHRN’s
Calculating Medications
Optional #3 – 2017
NAME: ___________________________________ DEPT. ______________________ DATE: __________
Convert the following weights into Kilograms (Kg) (don’t use field method):
1. 200 lbs.
_ ____________
2. 180 lbs.
_____________
3. 35 lbs.
_____________
4. 70 lbs.
_____________
5. 300 lbs.
_____________
6) You need to give an IM of Epinephrine 1mg/1ml. The dose required is 0.6 mg. What is the
amount of fluid that will be injected to the patient?
a. 0.006 ml
b. 0.06 ml
c. 0.06 mg
d. 0.6 ml
7) You need to give Diphenhydramine IM to a Pediatric patient. The Patient’s weight is 42 lbs.
The dosage is 1mg/kg. The Diphenhydramine is packaged 50mg/1ml. What is the dosage
and how much fluid will be injected into the patient?
a. 19 mg/0.38 ml
b. 22 mg/0.44 ml
c. 42 mg/0.38 ml
d. 42 mg/0.84 ml
8) You need to administer Amiodarone (2.5mg/kg) to a pediatric patient in V-Fib. The patient’s
weight is 110 lbs. The Amiodarone is packaged in 150 mg/3 ml. How much fluid of
Amiodarone will be administered in the IV?
a. 1.50 ml
b. 2.25 ml
c. 2.50 ml
d. 5.5 ml
9) You need to administer Atropine (0.02mg/kg) to a 44 lbs. pediatric patient. Atropine is
packaged 1 mg/10ml. What would the dosage amount be and how much fluid will be
administered in the IV?
a. 0.2 mg/ 2 ml
b. 0.4mg/ 4 ml
c. 0.5 mg/ 5 ml
d. 1.4 mg/ 14 ml
10) You are giving repeat dose of Adenosine to a 90 lbs. pediatric patient. The second dose is
0.2 mg/kg. The Adenosine is packaged in 12mg/2ml. What are the dosage and the amount
of fluid that will be administered in the IV?
a. 8.2 mg / 1.36 ml
b. 8.5 mg / 1.41 ml
c. 18 mg/ 2.0 ml
d. 20 mg/ 2.0 ml
11) You are setting up a Dopamine drip for a patient. You need to administer 5mcg/kg/min
using a 60 gtts/min drip set. The patient weighs 180 lbs. The Dopamine is packaged as
400mg/250ml. What are the drips per minute that will be given to this patient?
a. 9 gtts/min
b. 12 gtts/min
c. 15 gtts/min
d. 17 gtts/min
12) You are setting up a Dopamine drip for a patient. The patient weighs 180 lbs. You need to
administer 10mcg/kg/min using a 60 gtts/min drip set. The Dopamine is packaged as
400mg/250ml. What are the drips per minute that will be given to this patient?
a. 10 gtts/min
b. 15 gtts/min
c. 31 gtts/min
d. 62 gtts/min
13) You need to administer Ondansetron 0.15 mg/kg IM on a pediatric patient. The Pt. weight
48 lbs. Ondansetron is packaged 4 mg/2ml. What is the total amount of medication and
fluid that will be administered to this patient?
a.
1.0 ml
b.
1.7 ml
c.
2.0 ml
d.
2.5 ml
14) You are working V-fib on a pediatric patient. The Epinephrine you are going to administer is
1mg/10ml. The dose you will be giving is 0.01 mg/kg. The patient’s weight is 95 lbs. What
is the total amount of Epinephrine you will administer and what is the fluid amount?
a.
b.
c.
d.
0.50 ml
2.25 ml
3.30 ml
4.30 ml
15) You will be administering Magnesium 25mg/kg (Slow IVP). The Magnesium is packaged
2g/40ml. Your patient’s weight is 90 lbs. This will be given over 10 minutes. What is the
medication dosage and what is your drip rate per minute?
a. 1025 mg (1.0g), 20 ml, 120 gtts/min
b. 1475 mg (1.5g), 30 ml, 180 gtts/min
c. 1700 mg (1.7g), 34 ml, 204 gtts/min
d. 2000 mg (2.0g), 40ml, 240 gtts/ min
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