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Dosage Calculation Using Dimensional Ana

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Dosage Calculation Using Dimensional AnaPresentation Transcript

• Calculate with Confidence 5 th edition Gray Morris Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
• Dosage Calculation Using the Dimensional Analysis Method Unit Three: Chapter 16 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
• Dosage Calculation Using Dimensional Analysis Method: Objectives
• After reviewing this chapter, you should be
• able to:
• Define dimensional analysis
• Implement unit cancellation in dimensional analysis
• Perform conversions using dimensional analysis
• Use dimensional analysis to calculate dosages
• Background: Dimensional Analysis
• Fancy name—simple technique
• Used to manipulate units in a calculation
• Involves cancellation of unwanted units
• Eliminates need to memorize formulas
• Also known as the factor-label method or the unit factor method
• Only one equation is used
• Performing Conversions Using Dimensional Analysis
• Conversions can be made within process of calculation rather than in advance
• Equivalents or conversion factors are expressed as fractions written in one of two ways without changing meaning or value—e.g., CF: 1 kg = 1,000 g is the same as 1 kg/ 1,000 g or 1,000 g/ 1 kg
• Making Conversions Using Dimensional Analysis
• Identify desired unit
• Identify equivalent needed
• Write equivalent in fraction format with desired unit in numerator as first part of equation
• Label all factors in equation, with x being what you desire to have in the end
• Making Conversions Using Dimensional Analysis (cont’d)
• Identify unwanted or undesired units and cancel, then reduce to lowest terms
• Must be able to eliminate all labels except for answer label—if not, recheck
• Perform mathematical process
• Note: it is key to have the
• equivalent set up correctly!
• Making Conversions Using Dimensional Analysis (cont’d)
• Example: 1.5 g = _______ mg
• The desired unit is mg
• Equivalent: 1,000 mg = 1 g
• Write equivalent—keep mg in numerator (allows cancellation of unwanted unit, g)
• Write equivalent as fraction, add multiplication sign
• Perform calculation
•
• Dosage Calculation Using Dimensional Analysis
• Identify unit of measure (caps, mL, tabs) and place x on left with appropriate unit
• On right, place available information as a fraction — information matching the x unit will be placed in the numerator
• Enter additional factors — set up so unit of numerator matches preceding denominator
• Cancel out like units — remaining unit should match the unit for x — then calculate
• Dosage Calculation Using Dimensional Analysis (cont)
• Example: Order is Lasix 40 mg p.o. daily
• Available: 20 mg tablets
• Place desired unit of measure on left and label as x
• x = tab
• Dosage Calculation Using Dimensional Analysis (cont’d)
• Example: Order is Lasix 40 mg p.o. daily
• Available: 20 mg tablets
• Place the info in problem on right in fraction format—matching desired unit in numerator
• Dosage Calculation Using Dimensional Analysis (cont’d)
• Example: Order is Lasix 40 mg p.o. daily
• Available: 20 mg tablets
• Enter additional info (e.g., what is ordered), matching unit in numerator with preceding denominator
• Amount to administer Available dosage Ordered dosage
• Dosage Calculation Using Dimensional Analysis (cont’d)
• Cancel “like” units on right of equation; remaining unit of measure should be what is desired
• Dimensional Analysis Using Conversion Factor
• When a conversion factor is needed, the conversion factor is placed as the second fraction inside the equation
• Match numerator of conversion factor with denominator of previous fraction
•