Transcript Drug Math For Nurses

Drug Math For Nurses
Dimensional Analysis for Meds
Junior Level I
Summer 2011
Objectives
• At the conclusion of this presentation, students will:
• Have a general understanding of basic dimensional
analysis calculations for nursing drug math
• Verbalize basic medical terms for drug math
calculations
• Identify key points to review and understand before
taking 1st Drug Math Exam at UAMS College of
Nursing
Resources
• LRC [5th floor of library—Ed II)
– Computer Assisted Instruction (CAI) programs available in
the LRC during LRC hours
• www.atitesting.com - My E Learning - Tutorials - Meds
Made Easy
UAMS College of Nursing
Drug Math Examination Policy
Basics
• Students are required to take the drug math exam prior to each course with a
clinical component
• Students must score a minimum of 90% to pass the exam
• 3 opportunities to pass
– 1st two (2) attempts are computerized and proctored in the LRC (5th floor of
Library) during normal business hours
– If you do not score 90% or above on Exam 2, you must remediate with the Drug
Math Coordinator prior to taking exam 3 (Notify the Drug Math Coordinator
immediately after failing exam 2 to arrange remediation;
[email protected])
– 3rd attempt, if necessary, is arranged with the appropriate Drug Math Coordinator
• Practice Exams may be taken at home or in the LRC during normal hours
Metric Conversions
• You must be able to read the problem
– Know the terminology and abbreviations used
Metric & International System (SI)
Terms
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L = liter
mL = milliliter
cc = cubic centimeter
tsp = teaspoon
kg = kilogram
g = gram
mg = milligram
mcg = microgram
cm = centimeter
mEq = milliequivalent
gtt = drop
• PO = by mouth
Basic Conversions
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1 mL = 1 cc
1 ounce = 30 mL or 30 cc
1 tablespoon = 15 mL or 15 cc
1 teaspoon (tsp) = 5 mL or 5 cc
3 teaspoons (tsp) = 1 tablespoon
1 liter (L) = 1000 mL or 1000 cc
Basic Conversions
• 1 kilogram (kg) = 2.2 pounds
Medical Terms for
Medication Administration Times
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Q D = Every day (once per day)
BID = Twice daily
TID = Three times per day
QID = Four times per day
Q HS = At bedtime (once per day)
ac = before meals
pc = after meals
Relative Value of Decimals
• Values on the left side of the decimal are increasing in
value
100 is larger than 10.00
• Values on the right side of the decimal are decreasing in
value
0.1 is larger than 0.01
Relative Value of Decimals
1234.5678
Thousands
Ten Thousandths
Hundreds
Hundredths
Tens
Thousandths
Ones
Tenths
UAMS Rounding Rules
ml or cc:
If the answer is < 1cc (or ml) then
round to the nearest 100th.
Ex: 0.376 = 0.38 cc (or ml)
If the answer is > 1cc (or ml) then
round to the nearest 10th.
Ex: 1.57 = 1.6 cc (or ml)
Tablets:
Tablets, as a rule, can only be given
whole or broken in half. Round to the
nearest half (0.5)
Ex: 1.45 = 1.5 tablets 1.2 = 1 tablet
Round at the end of the problem, when you get to the answer (exception is
when you’re converting pounds to kilograms (kg)) then you should round
to the nearest tenth as soon as you convert, then complete the problem
(2.345 = 2.4)
UAMS Rounding Rules
Rounding Rules
Basic Rounding:
If the number is  5 then round up.
Ex: 1.57 = 1.6 1.45 = 1.5
0.686 = 0.69
If the number is < 5 then round down.
Ex: 0.543 = 0.54
Converting pounds and kilograms:
Round to the nearest 10th.
Ex: 120 pounds = 54.54 or 54.5 Kg
Remember:
Round at the end of the problem.
The exception to this rule is when
you are converting pounds to
Kgs. Always convert and round to
the nearest 10th and then
complete the problem.
UAMS Rounding Rules
• Basically it means, when you’re working a problem,
don’t forget to round your answer at the end (when you
get your answer) The computer is very specific and
will count you wrong if you round wrong!!
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0.345 mL = 0.35 mL (answer is < 1 mL)
1.345 mL = 1.4 mL (answer is > 1 mL)
0.99 mL = 0.99 mL (answer is < 1 mL)
0.995 mL = 1 mL (answer is 1 mL or greater)
Basic Math Review
• Fractions
1
---4
(numerator)
(denominator)
Convert Fraction to Decimal
1
--- =
4
____
4) 1
=
0.25
4 ) 1.00
8
20
20
0
Convert Fraction to Decimal
1
--- =
3
0.3333
3 ) 1.0000
9
10
9
10
9
10
9
10 infinite
Convert Pounds to Kilograms (kg)
• You are caring for a
patient that weighs 73
pounds. How many
kg does this person
weigh? _______
Convert Pounds to Kilograms (kg)
• You are caring for a patient that weighs 73
pounds. How many kg does this person weigh?
_______
• We know 1 kg = 2.2 pounds
Convert Pounds to Kilograms (kg)
• You are caring for a patient that weighs 73
pounds. How many kg does this person weigh?
__33.2 __
• We know 1 kg = 2.2 pounds
• 73 divided by 2.2 = 33.181818 = 33.2 kg
round to nearest tenth
Convert Pounds to Kilograms (kg)
Hints
• When you convert pounds (larger number) to kilograms
(smaller number) your answer will always be smaller
– 100 pounds (divided by) 2.2 kg/pound = 45.5 kg
• When you convert kilograms (smaller number) to
pounds you need to multiply; your answer will always
be larger
– 10 kg X
2.2 pounds/kg = 22 pounds
Reading Drug Labels
• Drug name will be available
– Generic
– Trade
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Container size
Concentration (unit of measure)
Lot number
Expiration date
Additional Information
– Manufacturer
– Safety Precautions (but not always)
Reading Drug Labels
• Find the concentration (unit of measure) of the
drug
– How many mg is in each tablet?
– How many mg is in how many mL of the solution?
– Example
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The drug is supplied as 750 mg per 5 mL
The available dosage strength is 1 gram in 3.5 mL
Pharmacy sends 325 mg tablets
The drug available is 500 mg per tablet
Reading Drug Labels
• Sometimes, you may be confused by a question
that gives you “extra” information, like telling
you how large the container is
– Example
• The nurse has a 500 mL bottle or Drug A at a strength of
30 mg per teaspoon
• What does this mean???
Reading Drug Labels
• The nurse has a 500 mL bottle or Drug A at a strength
of 30 mg per teaspoon
• What does this mean?
– It means you have a bottle that contains 500 mL of Drug A
– Each teaspoon (5 mL) contains 30 mg of Drug A
– So, the entire bottle contains 3000 mg of Drug A
• 500 mL (divide by) 5 mL = 100 X 30 mg = 3000 mg
Reading Drug Labels
• For dosage calculation, you need to be able to find the
concentration (unit of measure) even when more information is
given than needed
– Take the same example
• The nurse has a 500 mL bottle or Drug A at a strength of 30 mg per teaspoon
• The concentration (unit of measure) is 30 mg per teaspoon; the
500 mL is “extra” information that you don’t need in order to
calculate how many mL to give
– Remember, 1 tsp = 5 mL, so you have 30 mg/5 mL
Dimensional Analysis
Steps
• Find the unit of measure being calculated and write it,
then put an equal = sign
– This guides you so you know where to put each piece of
information; Very important step
• Example
mL =
tab =
Dimensional Analysis
2nd step
• Find what you have on hand [the concentration
of drug (unit of measure)]
– Example
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100 mg per 5 mL
0.125 mg per 3.5 mL
500 mg per tablet
1 gram / 10 mL
2 grams / 1 ounce
Dimensional Analysis
2nd step continued
• This is placed in the first spot right of the equal sign as
a ratio (clinical ratio)
• The numerator must match the unit of measure being
calculated
– Example
5 mL
mL = --------100 mg
numerator
denominator
Dimensional Analysis
3rd step
• The unit of measure in each denominator must be
matched in the successive numerator entered
– Example
• If the doctor orders 50 mg of Drug A (previous slide). The
concentration was 100 mg/5 mL
successive numerator
numerator
5 mL
mL = ---------100 mg
denominator
X
50 mg
-----------
Dimensional Analysis
Final Step
• Cancel out common denominator & numerator
• Cancel out common terms (mg, gram & so on)
– Example
5 mL
mL = ---------100 mg
2
1
X
50 mg
-----------
Dimensional Analysis
• Now, do the math to get your answer
– Remember your rounding rules
1
5 mL
mL = ---------100 mg
2
50 mg
5
X --------- = ---- = 2.5 mL
2
Dimensional Analysis
• Prepare a 500 mg dose of Vancomycin from an
available solution of 1000 mg per 3 mL.
3 mL
500 mg
mL = ------------ X ---------- =
1000 mg
Dimensional Analysis
1
3 mL
500 mg
mL = ------------ X ---------- =
1000 mg
2
1st reduce the common numerator & denominator
Dimensional Analysis
1
3 mL
500 mg
mL = ------------ X ---------- =
1000 mg
2
next, cancel out “like terms”
Dimensional Analysis
1
3 mL
500 mg
3
mL = ------------ X ---------- = ---- = 1.5 mL
1000 mg
2
2
Last, do the math!
Dimensional Analysis
• If you need to do a metric conversion, it is added to the
equation in the middle
– Example
1 tab
tab = --------1 gram
X
500 mg
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As you can see, we can’t cancel out any “like terms”
Dimensional Analysis
• Metric Conversion
1 tab
tab = --------1 gram
500 mg
X ----------1 gram
1000 mg
• We know that 1 gram = 1000 mg, so we can put this into the
equation (in the middle)
Dimensional Analysis
• Metric Conversion
1 tab
1 gram
500 mg
tab = --------- X ----------- X ----------- =
1 gram 1000 mg
Dimensional Analysis
• Metric Conversion
1
1 tab
1 gram
500 mg
tab = --------- X ----------- X ----------- =
1 gram 1000 mg
2
Now we can cancel out and reduce commons
Dimensional Analysis
• Metric Conversion
1
1 tab
1 gram
500 mg
1
tab = --------- X ----------- X ----------- = --- = 0.5 tab
1 gram
1000 mg
2
2
Last, do the math for your answer!!
Insulin Administration
– Insulin is always ordered in units
– Do not abbreviate units as U, it must be spelled out to
prevent medication errors
– Insulin is supplied in U-100 doses
• 1 unit = 0.01 mL
• 10 units = 0.1 mL or 0.10 mL
• 100 units = 1 mL
– You must use specially marked syringes [they are usually
orange color] to give insulin (they are called insulin syringes);
do not draw up insulin in a standard syringe