## Fousmc03_0131134604.qxd

FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 49 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: Calculating the cc’s
LEARNING THE FORMULA
Now that the first two steps of this formula have been learned—identifyingand calculating the desired dose, and calculating the concentration—we canproceed to the third step.
STEP 3
Calculate the amount of cc’s to be delivered.There are two purposes for this
particular calculation: (1) when giving a drug through SQ, IM, IV, ET, or IO
it is necessary to calculate the amount of cc’s to be drawn from a particular
container (ampule or vial) or to be pushed through a prefilled syringe so that
the desired dose can be delivered, or (2) to calculate the amount of cc’s
needed to figure gtts/min, which is required in step 4, on calculating drip
rates. For whichever reason cc’s are being calculated, the formula is:
If the route of administration is SQ, IM, ET, IO push, or IVP, only the first three steps of this formula, (1) DD, (2) C, and (3) DD/C, need to becalculated, eliminating step 4, which is defined in chapter 4. The reason for FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 50 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: eliminating step 4 when the route of administration is SQ, IM, ET, IO push,or IVP is that ultimately you need to calculate only the number of cc’s to drawfrom a given container, not the drops per minute, as required for a dripadministration. If a prefilled syringe is being used, it is necessary to calculateonly the number of cc’s to push from the syringe.
This step can be very simple because all it involves is dividing the desired When dealing with this step, many times there are several zeros in these
To simplify the division process in the above example, some zeros can be canceled out. When canceling zeros, the same number of zeros must be
canceled in both the numerator (top number) and denominator (bottom
number). See example:
In the above example, one zero was able to be canceled in both the nu-
merator of 500 and the denominator of 50. Another example of canceling out
zeros follows:
In this last example, two zeros were able to be canceled in both the
Because zeros can be canceled out, measurements also can be canceled.
After canceling the mg’s, the only measurement left is cc. So the answer
will be in cc’s, as noted in the previous example.
Following are a few examples on the calculations involved in step 3.
FOUSMC03_0131134604.QXD 12.17.03 6:35 M Page 51 RK UL-15 RKU L-15:Desktop Folder:PUR N_FOUST_16_12:CH03: You have been ordered to give 2.5 mg of valium. On hand is a vial
with 2 cc containing 10 mg. How many cc’s would you draw?
DD ϭ 2.5 mg
Explanation: First you identified the desired dose, which was 2.5 mg.
Then, in step 2, you calculated the concentration by dividing 10 mg by 2 cc
(remember, mg over cc [mg/cc] when calculating the concentration), leaving
5 mg/cc. Then, in step 3, the desired dose of 2.5 mg was divided by the con-
centration of 5 mg/cc. So 2.5 mg divided by 5 mg/cc equals .5 cc (remember
that the mg’s canceled), leaving cc as the only measurement.
You have been ordered to give 1 mg/kg of Lidocaine IV. Your patient
weighs 150 pounds. The prefilled syringe contains 100 mg in 5 cc. How
many cc’s will you push?
DD = 1 mg/kg 2.2 ͤ1500 68 * 1 mg = 68 mg
DD ϭ 68 mg
Explanation: In the previous example, the desired dose was ordered per
kg. So, first the pounds were converted to kg (by dividing the 150 pounds by 2.2),
leaving an answer of 68 kg. You then multiplied the total number of kg, which
was 68, by the desired dose per kg, which was 1 mg per kg, leaving a desired dose
of 68 mg. In step 2, you calculated the concentration by dividing the number of
mg’s by the number of cc’s of the on-hand drug, which was supplied in a pre-
filled syringe. In step 3, you divided the desired dose by the concentration. The
mg’s canceled out, leaving you with 3.4 cc to push from the prefilled syringe.
The physician has ordered 20 mg of Lasix IV. On hand is a vial with
4 cc containing 40 mg. How many cc’s will you give?
DD ϭ 20 mg
FOUSMC03_0131134604.QXD 12.17.03 6:35 M Page 52 RK UL-15 RKU L-15:Desktop Folder:PUR N_FOUST_16_12:CH03: Explanation: First you identified the desired dose of 20 mg. In step 2,
you took your on-hand medication supplied in the vial and divided the mg’s
by the cc’s. In step 3, you divided the desired dose by the concentration. The
mg’s canceled, leaving an answer of 2 cc. This amount would then be drawn
THE TIME FACTOR
Note that when a drip has been indicated for a particular drug administra-
tion, the desired dose will be ordered over a certain time frame, normally per
minute. See examples:
10 ␮g/kg/min
You should never leave out any part of the problem to “cut corners”
when calculating on paper. Consistently label each number or figure accord-
ingly. See examples:
DD ϭ 2 mg/min
C ϭ 4 mg/cc
DD ϭ 10 ␮g/kg/min
C ϭ 800 ␮g/cc
Never leave out any measurements or time factors. Failure to include any identifying factors, such as DD ؍, C ؍, DD/C ؍, mg’s, cc’s, or minutes,will only confuse and complicate the calculation learning process.
Concerning step 3 of this formula on calculating cc’s, if a time factor has
been given in the desired dose, be sure to always include it throughout each
step, especially this one. But don’t let the time factor confuse you, because it
has absolutely nothing to do with the calculation of this step. However, it has
everything to do with step 4. This is why it is so important not to leave this
factor out at any time throughout your calculations.
Again, be sure to place it (min) properly in the equation, but disregard
it when figuring your math through step 3. See example: DD ϭ 2 mg/min
.5 cc/min
In reference to the preceding example, cc’s is the only measurement left
after canceling the mg’s. The time factor always goes on the bottom of any
answer throughout any equation. See example:
1Top2 2 mg/min (bottom) ϭ (Top) .5 cc/min (bottom)
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 53 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: Since the minute is part of the desired dose, it must remain with the
desired dose, as noted in 2 mg/min, until you have calculated the answer in
step 3 of the formula.The time factor then moves to the bottom in the answer
in step 3, as shown previously in .5 cc/min.
When calculating cc’s to further be used in the calculation of step 4, your
answer will usually involve decimal fractions, especially in drips such as
Dopamine. When this is the case, it is necessary that you divide only to the
nearest 1000th, which is the third decimal fraction (.222). Rounding off to the
nearest whole number is not suggested at this point when working with drip
calculations. See examples:
= .187 cc/min DD =
= .212 cc/min
SUMMARY
Just as you have learned, the third step of this process consists simply of
dividing the desired dose by the concentration. Always remember to label
figures and equations and don’t “cut corners.” This will only confuse you. So
far, three of the four steps consists of:
C (always weight/cc)
e.g.—mg/cc
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 54 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: Following are a few practice questions pertaining to step 3. Simply completethe first three steps of the formula that you have learned so far. Remember,some of the answers may seem obvious to you, but it would be very much toyour advantage to work out each and every step.
An order has been given for a particular drip delivering 10 g/min. On
hand is 1 mg, a 250 cc bag of fluid, and a minidrip administration set.
How many cc’s per minute must be delivered to give the DD?
You have been ordered to give 8 mg of Decadron IV. On hand, you have
a 5 cc vial containing 20 mg. How many cc’s must you draw to give your
DD?
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 55 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: A physician has given you an order for a Lidocaine drip to be run at
2 mg/min. On hand are two grams of Lidocaine, a 500 cc bag of normal
saline, and a minidrip administration set. How many cc’s per minute
must be delivered to give the DD?
The doctor has ordered you to give 25 mg of diphenhydramine IV. On
hand is a 2 cc vial containing 50 mg. How many cc’s must you draw to
give the DD?
You are at the residence of a patient who requires a dopamine drip.
pounds. On hand is 400 mg of dopamine, a 500 cc bag of normal saline,
and a minidrip administration set. How many cc’s per minute must be
delivered in order to give the DD?
You are on scene with a 1-year-old male requiring 1 mg/kg of Lidocaine
IV. The mother advises you that her son weighs 22 pounds. Your Lido-
caine comes supplied in a prefilled syringe containing 100 mg in 5 ml.
How many ml’s would you administer?
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 56 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: You have been ordered to give 12 mg of Decadron IV. On hand is a vial
containing 20 mg in 5 cc. How many cc’s would you give?
You are en route to the hospital and your patient requires 6 mg of
adenosine rapid IVP. On hand is a 2 cc vial containing 6 mg. How many
cc’s would you draw?
A dopamine drip has been ordered to be run at 8 g/kg/min. On hand
is a vial containing 400 mg, a 250 cc bag of normal saline, and a minidrip.
If your patient’s weight is 145 pounds, how many cc’s per minute would
you deliver?
A Lidocaine drip has been ordered to be run at 3 mg/min. On hand you
have a vial containing 1 gm, a 250 cc bag of normal saline, and a minidrip.
If your patient weighs 220 pounds, how many cc’s per minute do you
need to give?
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 57 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: DD ϭ 10 g/min
C ϭ 1 mg/250 cc ¡ 1 0 0 0 ␮g/250 cc ϭ 4 g/cc
= 2.5 cc/min
C ϭ 20 mg/5 cc ϭ 4 mg/cc
DD ϭ 2 mg/min
C ϭ 2 gm/500 cc ¡ 2 0 0 0 mg/500 cc ϭ 4 mg/cc
= .5 cc/min
DD ϭ 25 mg
C ϭ 50 mg/2 cc ϭ 25 mg/cc
FOUSMC03_0131134604.QXD 12.16.03 6:58 PM Page 58 RKAUL-15 RKUAL-15:Desktop Folder:PURAN_FOUST_16_12:CH03: DD = 2 ␮g/kg/min ¡ 2.2 ͤ2200
DD ϭ 200 µg/min
C = 400 mg/500 cc = .8 mg/cc
¡ .8 mg ¡ 8 0 0. µg ϭ 800 µg/cc
= .25 cc/min
DD = 1 mg/kg ¡ 2.2 ͤ220 ¡ 10 * 1 mg = 10 mg
C ϭ 100 mg/5 ml ϭ 20 mg/ml
DD ϭ 12 mg
C ϭ 20 mg/5 cc ϭ 4 mg/cc
C ϭ 6 mg/2 cc ϭ 3 mg/cc
65.9 ¡ 66 kg
DD = 8 ␮g/kg/min ¡ 2.2 ͤ1450
DD ϭ 528 µg/min
C = 400 mg/250 cc ϭ 1.6 mg/cc
1.6 mg ¡ 1 6 0 0. ␮g ϭ 1600 g/cc
= .33 cc /min
10. STEP 1
DD ϭ 3 mg/min
C ϭ 1 gm/250 cc ¡ 1 0 0 0 mg/250 cc ϭ 4 mg/cc
= .75 cc/min