Transcript Dimensional Analysis Study Guide

• In any drug calculation problem, for exam
purposes, if you do not include the proper
unit in your answer; it will be WRONG!
• If you do not show your work in dosage
calculation on the Exams, your answers will be
considered wrong !
• ***Remember You may have to perform
several conversions before you can obtain the
answer you are seeking ***
• For oral things like tablets, capsules, etc. Remember DO/DA
• Dose ordered x desired med (cap, tab, ml) = amount to be given
Dose Available
• Weight Based Problems
• When mg/kg/day is ordered, this is not a division problem, it
is a multiplication problem
• Intravenous fluid must be set for a given rate
• It must be measured as ml/hour, L/hour or drops/min.
• To control or adjust the flow rate only drops per minute are used.
• The formula for working out flow rates is:
•
Volume (mL) x drop factor gtt (drips)= Rate (gtt/min) (MUST be whole number
•
Time (min)
mL (Volume)
)
Steps
• Determine what you want to know.
• Read the problem
• What is it asking?
• Determine what information you already know.
• Setup the problem using only what you need to know.
– Pick a starting point
• pick from what you know and make sure you put it in the right
place
• Or pick a factor that is given, such as what the physician ordered.
• Be aware that the starting factor will always have at least
one unit that is not desired.
• This will need to be changed using a cancellation technique
• Keep trying to cancel out units you don't want until you end up
with only the ones you do
• If you can't get to what you want:
• try picking a different starting factor
• Did you Convert everything?
It is time to Solve It: Make sure all the units other than the answer
units cancel out, then you are ready to do the math.
a. Simplify the numbers through cancellation.
Same number on top and bottom: these should cancel
out
b. Multiply all the top numbers together, then divide into that
number all the bottom numbers..
Don’t Put the decimal in the wrong spot.
Don’t add incorrectly
always double check.
d. Round off the calculated answer if possible.
•
e. Add labels to the appropriately rounded number to get your
answer.
• Always work the problem backwards to check accuracy.
• You need to start a continuous drip of amiodarone at 1 mg per minute (by
pump). The standard IV mixture is 450 mg in 250 mL.
• Pumps like to be programmed in mL/hr, so mL/hr are your answer units.
• 1mg x 60min x 250ml = 33.3ml/hr
• 1min 1 hr
450mg
•
Milrinone Lactate (Primacor) has been ordered for a patient at 0.4
mcg/kg/min. The patient weighs 145 kg. If the pharmacy mixes 20 mg of
Milrinone in 100 mL of total solution, what would be the rate of the
infusion?
• First, think what units will be in the answer. Since you're using a pump, it's
mL/hr.
•
• 145kg x 0.4mcg x 1mg
x 1 00ml x 60min= 17.4ml/hr
1kg/1min
1000mcg
20mg
1hr
Practice
1. Calculate the drip rate for 100 mLs of IV
Fluids to be given over a half hour via a giving
set which delivers 10 drops/ml.
2. Calculate the drip rate for 2 liters of IV Fluids
to be given over 5 hours via a giving set
which delivers 10 drops/ml.
3. A client is ordered 20 milligrams of Haloperidol
decanoate by intramuscular injection. 50
milligrams in 1 milliliter of liquid for IM Injection
is available. How many milliliters will you
administer?
4. A client is ordered 200 milligrams of Augmentin
600 intravenously. 600 milligrams in 6 milliliters
of liquid for IV Injection is available. How many
milliliters will you administer?
• 5. The IV ordered is 1000 mL to infuse at 160
mL/hour. Calculate the infusion time in hours
and minutes for this order
6. The order is for nitroprusside 50 mg in 250 mL
D5W to infuse at 3 mcg/kg/min for a patient
whose weight is 75 kg. Calculate the hourly
infusion rate in mL/hr.
7. The order is for dopamine 200 mg/500 mL D5W
to infuse at 10 mcg/kg/min for a patient whose
weight is 75 kg. Calculate the hourly flow rate in
mL/hr.
8. The physician orders dopamine (Intropin) 400 mg
in 250 mg D5W TRA 5 mcg/kg/min.
For the client who weighs 110 lbs, how many
ml /hr will the pump be set?
9. Nitroglycerin is infusing at 16 ml/hr. The bag has 50 mg NTG
in 250 ml D5W. How many mcg/min is the client receiving?
10.Ms. Bellman is post-op CABGx5. She has an order of
dobutamine 3 mcg/kg/min. The 250 ml bag of D5 indicates
250 mg of Dobutrex. Her weight is 130 lbs. What is the flow
rate?
11. Mr. Muruski is being treated for shock. The dobutamine
infusion is set at 34 ml/hr. The medication label indicates
Dobutrex 250 mg in 250 ml D5. His weigh is 190 lbs. What is
the dosage of dobutamine the client is receiving?
Answers
1.
2.
33gtts/min
67 gtts/min
3.
0.4 ml
4.
= 2 ml
5.
•
1000ml x 1 hr
= 6.25 hours
160ml
then .25hrs x 60min = 6 hours and 15 mins
1 hour
6.
3mcg/75kg/60min= 13500mcg/hr or 13.5mg/hr
250ml x 13.5mg = 68mL/hr
50mg 1 hr
7. 10mcg/75kg/60min= 45000mcg/min or 45mg/hr
• 500ml x 45mg =112.5 or 112ml/hr
• 200mg 1 hr
8. 400 / 250 = 1.6 mg/ cc = 1600 mcg/cc 2)
Convert lbs to kg. 110 / 2.2 = 50 3)
Dose (5) x kg (50) x 60 / concentration (1600) 5 x 50 x 60 = 15,000 15, 000 /
1600 = 9.375
9. 50 / 250 = 0.2 mg/cc = 200 mcg/cc
Rate (16) x Concentration (200) = 3200 / 60 = 53.33
10. 59 kg Concentration is 1000 mcg/ml.
11. Wt. = 86.36 kg. Concentration = 1000 mcg/ml (34 x 1000) / (86.6 x 60)