dosage calculations using dimensional analysis anyone can do it!
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Dosage Calculations Using Dimensional Analysis
Anyone can do it!
Outcomes:Understand the learning components needed for student success in performing dosage calculations.Utilize dimensional analysis to calculate dosage.Potential resources for teaching dimensional analysis in the classroom.
Ways to calculate dosage:Formula Method
VH
DAmount to Give
Challenge: Must remember the extra step of changing D and H to same unit of measurement. Also may have extra variables such as body weight, times per day, etc.
Ways to calculate dosage:Ratio and Proportion
Linear Ratio and Proportion
Fractional Ratio and Proportion
500mg : 1 tab :: 1 g : x tabsProduct of the means equals the product of the extremes.
xtabs
g
tab
mg 1
1
500
The products of cross multiplication in a proportion are always equal
Dimensional AnalysisDimensional Analysis involves setting up a series of fractions.
All information is in one problemStudents do not have to remember multiple stepsStudents ask four simple questions to set up their dimensional analysis problem.
Necessities for Student Success in Dosage Calculations
Review of basic math functions – fractions and decimals
AddingSubtractingMultiplicationDivision
Students must memorize equivalents
The 4 main questionsWhat is the order?What is on hand?Do you need any equivalents?Where are you going? (or what are you being asked to give?)
Start with conversions
240 mg = ______ grains
240
1
mg
Start with conversions
240 mg = ______ grains
240
1
1
60
mg grain
mg grains
1
4
4
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
What is the order?
dose
mg
1
40
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
What is on hand?
dose
mg
1
40mg
ml
80
10
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
Do you need any equivalents?
dose
mg
1
40mg
ml
80
10
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
Where are you going? (or what are you being asked to give?)
mlmg
ml
dose
mg________
80
10
1
40
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
Begin by cross canceling labels
mlmg
ml
dose
mg________
80
10
1
40
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
Labels left should be “what you are looking for”
mlmg
ml
dose
mg________
80
10
1
40
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
Do the math
mlmg
ml
dose
mg________
80
10
1
40
1
2
55
1
What about problems with different units of measurement?
Order: digoxin elixir 0.05 mg PO dailyLabel: Digoxin 50 mcg per mlHow many milliliters will you give?
dose
mg
1
05.0mcg
ml
50
1
mg
mcg
1
1000 ml
1
20
1
Complex Problems
Order: Augmentin 12.5mg/kg PO every 12 hours. Child weighs 22 lbs. Pharmacy sends a 75 ml bottle of Augmentin labeled 125mg/5ml. How many milliliters will you pour from the bottle?
dosekg
mg
/
5.12
mg
ml
125
5
lbs
kg
2.2
1
.1
22
pt
lbs ml
5275
1375
1
22
2.2
1
125
5
1
5.12
5
What about IV problems?Order: 250ml 5% D/W IV in 2.5 hours.Tubing package reads 15 gtts/ml.How many gtts/min will you adjust the IV?
hrs
ml
5.2
250ml
gtts
1
15
.min60
1hr
min___
gtts
25150
3750
60
1
1
15
5.2
250
25
Physicians order Daypro 1200 mg bid.
mg
cap
dose
mg
600
1
1
1200
1
2
cap2
Order: Estratab 1250mcg daily
mcg
mg
mg
tab
dose
mcg
1000
1
25.1
1
1
1250tab
11250
1250
1000
1
25.1
1
1
1250
1
The order reads: Administer 1000cc of D5NS over 10 hrs. The drop factor on your tubing is 15 gtts/cc.
How many gtts/min?
hours
cc
10
1000
cc
gtts
1
15
min60
1hourgtts/min
1
4
1
25
25
or
25600
15000
60
1
1
15
10
1000
Practice Problems
Your patient may receive Dilaudid 3 mg IM q3h for pain. Dilaudid is supplied in 1-ml ampules containing 4 mg. How many milliliters will you administer?
3
1
mg
dose
1
4
ml
mg ml¾= 0.75
The physician orders heparin 2500U subq. You have heparin, 5000U per ml. How many ml will you administer?
2500
1
u
dose
1
5000
ml
u ml
1
2
1
2
Your patient needs morphine gr 1/6 SQ stat for chest pain. You have a 20 ml vial labeled 15mg/ml. How many milliliters will you give?
1 6
1
/ gr
dose 1
15
ml
mg
60
1
mg
gr ml
1 6 60
15
60 6
15
10
150 67
/ /.
x
0.67
A patient with tachycardia has an order for Brevibloc to be started at 50 mcg/kg/min. The concentration is Brevibloc 5 g in 500ml of D5W. The patient weighs 176 pounds. How many ml/h should the IV pump be programmed for?
50mcg
kg / min
500
5
ml
g ml/hr
176
1
lbs
pt
.
.
1
2 2
kg
lbs.
1
1000
mg
mcg
1
1000
g
mg
60
1
min
hour
50
1
500
5
176
1
1
2 2
1
1000
1
1000
60
1
.
1
2
1
251
401
80
1
2
1
12
24
24
Resources for teaching Dimensional Analysis
IV Calculations site
http://www.geocities.com/Heartland/Valley/3049/iv/clcltns.html
Math tutorials
http://www.utep.edu/nurs4710/tutorials/
IV drip rate problems and dosage calculation problems
http://www.dalesplace.net/iv.htm
Nursing Math Simplified“Math Magic”
Author: Susan Garner MooreISBN: 0-943202-22-1
53 page book – basics on what they call “Math Magic”
Quick & Easy Dosage Calculations
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Product Details Paperback: 318 pages ; Dimensions (in inches): 0.75 x 10.00 x 8.50 Publisher: W B Saunders; 1st edition (February 15, 1999) ISBN: 0721671330
Clinical Calculation Made Easy
Clinical Calculations Made Easy: Solving Problems Using Dimensional Analysis : Softbound By Gloria CraigEdition: SecondISBN: 0-7817-3099-6Pub Date: February 2001 Pages: 272Illustrations: 245
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Dimensional Analysis for Meds
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ISBN: 076685938XFormat: Paperback, 319ppPub. Date: November 2001
Publisher: Delmar LearningEdition Description: 2ND BK&CDREdition Number: 2
Dosage CalculationsDosage Calculations : A Simplified ApproachBillie Ann Wilson, Billie E. Wilson, With Margaret T. Shannon
ISBN: 083859297XFormat: Paperback, 219ppPub. Date: December 1996Publisher: Appleton & LangeEdition Description: 3rd EditionEdition Number: 3
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