Transcript Math Competency Dimensional Analysis

Math Competency
Dimensional Analysis (DA)
Patricia Kelliher RN, MS
NUR 1020B
[email protected]
Office B building
What are the “7 rights” of medication
administration?
Resources
• Cookson, K. (20013). Dimensional analysis:
Calculate dosages the easy way. Nursing 2013,
(43) 6, 57-62. www.Nursing2013.com on
eLearning
• Miller Wilson, K. (2013). The nurse’s quick guide to
I.V. drug calculations. Nursing made Incredibly Easy,
?, 1-2 (“online exclusive”)
www.NursingMadeIncrediblyEasy.com
• Koharchik, L. and Hardy, E. (2013). As easy as 1,2,3!
Dosage calculations. Nursing made Incredibly Easy,
½,25-29. on eLearning
Why dimensional analysis to solve
dosage calculations problems?
• QSEN competencies: safety
• Logical format that can be used for ALL types of
calculations
– without memorization of formulas
– Factors (mL, mg) must be labeled to use the method
• Rationale:
– enhances a conceptual understanding
– improves accuracy
– and prevents medications dose errors
MA Nursing Core Competencies
CCP 2013
Dosage calculation review
• All dosage calculations have 2 main components:
– Medication dosage prescribed by the HCP, 100 mg
– Medication concentration via pharmacy,
50 mg/tablet
• Concentration is NOT a fraction but is set up as a numerator
(top) and denominator (bottom) factors and can be flipped
• Calculations – measure (or labels) in the numerators will
cancel out the same units of measure (or labels) in the
denominator
Dosage calculation review
• The goal is to set up the equation to cancel
out all the units of measure (labels) NOT
needed in the answer
– Prescribed: acetaminophen 650 mg PO
every 4 hours prn
– Supplied: acetaminophen 325 mg tablets
– How many tablets?
Tablets ? =1 tablet X 650 mg = 650 = 2 tablets
325 mg
325
Dosage calculation steps
• Determine the unit of measure (label) needed
– Tablet ?
• Place the information with the same label in the
numerator (top) position
– Tablet = 1 tablet
325 mg
• Place the information with the same label in the
preceding denominator into the numerator position
– Tablet = 1 tablet X 650 mg
325 mg
• Cancel out the label(s) and complete the math
(multiply and then divide) Tablet = 1 tablet X 650 mg = 650 = 2 tablets
325 mg
325
Summary
• Start with the labels needed in the answer
• Build the calculation until all labels not
needed in the answer are cancelled out
• Perform the arithmetic to determine the
correctly labeled answer
• Round only with the final answer
• PRACTICE
Know the Conversions
metric = increments of 1000
move the decimal point right or left by 3 spaces
• 1 kg = 1,000 g
3.5 kg = 3,500 g
• 1 g = 1,000 mg
0.5 g = 500 mg
• 1 mg = 1,000 mcg 0.25 mg = 250 mcg
• 1 L = 1,000 mL
0.5 L = 500 mL
• kilogram = gram = milligram = microgram
Conversions continued
• 2.2 lb = 1 kg
• 1 grain = 60 mg
• 1 ounce (oz) = 30 mL
Practice
oral medications
• Prescribed: potassium chloride 30 mEq PO
• Supplied: potassium chloride 40 mEq / 15 mL
• ? mL =
Practice
oral medications
• Prescribed: digoxin 0.125 mg PO
• Supplied: digoxin 0.25 mg / tablet (tab)
• ? Tab =
Practice
injectable medications
• Prescribed: nalbuphine 15 mg SC now
• Supplied: nalbuphine 20 mg/mL
• ? mL =
Practice
injectable medications
• Prescribed: cefazolin sodium 250 mg IM now
• Supplied: cefazolin sodium 1 g/3 mL (OR 1000
mg)
•? =
Practice
basic IV calculations
• Prescribed: cephalexin 1 gm piggyback every 8 hr
• Supplied: cephalexin 1 gm in 50 mL D5W (NS) to
infuse over 30 minutes
• All IV infusions are mL/hour
• ? mL =
hr
Practice
basic IV calculations
• Prescribed: regular insulin at 7 units / hr IV
• Supplied: regular insulin 100 units in 100 mL NS
•?
Practice
*** basic IV calculations
• Prescribed: nitroglycerin 5 mcg/minute IV
• Supplied: nitroglycerin 50 mg in 500 mL NS
•?
Practice
complex weight-based IV calculations
• Prescribed: heparin 15 units/kg/hour IV
• Supplied: heparin 25,000 units/250 mL D5W =
100 units/ 1 mL
(found on the pharmacy label)
• Patient weight: 195 lb = _____ kg
• ?
Practice
complex weight-based IV calculations
• Prescribed: dopamine 3 mcg/kg/minute IV
• Supplied: dopamine 800 mg in 250 mL NS
• Patient weight: 167.5 lb
•?
• Conversion move the decimal point
Practice
complex weight-based IV calculations
• Prescribed: propofol 20 mcg/kg/minute IV
• Supplied: propofol 15 mg/mL
• Patient weight: 217 lb
•?
Practice
1. Prescribed: nifedipine 30 mg PO daily
Supplied: 10 mg tablets
Answer _____
2. Ordered: cefazolin (Ancef) 750 mg (IM)
On hand; cefazolin (Ancef) 225 mg / mL _____
3. meperidine (Demerol) 75 mg IM Stat
meperidine 50 mg/mL
_____
4. Ordered: heparin 2500 units SC every 8 hours
heparin 5000 units / mL
_____
Practice
Calculation of gtt/min rates
• Prescribed: Infuse 125 mL per hour using
an IV drip set at 10 gtt/mL.
• ? gtt =
min
• Reduce the numbers in the set-up when
possible.
Practice
Calculation of gtt/min rates
• Prescribed: A 20 gtt/mL set is to be used to
infuse at a rate of 90 mL/hr. Calculate the
gtt/min flow rate.
• ? gtt =
min
Practice
Calculation of gtt/min rates
• Prescribed: Calculate the gtt/min flow rate to
administer an IV at 100 mL/hr using a set
calibrated at 15 gtt/mL.
• ? gtt =
min
Practice
Calculation of gtt/min rates
• Prescribed: Calculate the gtt/min flow rate for
100 mL to be infused in 40 min using a set
calibrated at 15 gtt/mL.
• ? gtt =
min
Formulas
do NOT promote understanding or future retention
• Basic dosage calculation:
D (desired dose) x Q (quantity) ==Dose
H (amount on hand)
• IV drips:
1. Total volume to be infused X drop factor = gtts/min
Total time in minutes or hours
2. Drips in units / hour
D (desired dose) x V (volume)=units/hour (# mL X units/mL=dose)
H (amount on hand)
Next class
• Continued review of handouts, eLearning