converting within and between systems
TRANSCRIPT
1Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
2Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
3Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
After reviewing this chapter, you should be
able to:1. Convert a unit of measure to its
equivalent within the same system2. Convert approximate equivalents
between the metric, apothecary, and household systems of measure
4Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Equivalents are not exact Several tables are available and may
vary› For example, gr i = 60-65 mg› 60 mg is used in most cases, but 65 mg is
best for aspirin conversions Memorization of equivalents (Table 8-1)
is essential for proficiency and communication with clients about medication administration
5Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
6Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Changing from one form to another Within same system (e.g., mg to mcg) Between systems (e.g., oz to mL) Result is approximate, but continuity
exists
7Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
1. Memorization is essential2. Think of equivalents as ratios
› 1 g = 1,000 mg is a ratio 1 g : 1,000 mg or 1:1,000
3. Follow basic math rules for all systems
4. Express answers using specific rules related to system to which conversion is being done (e.g., decimals for metric)
5. THINK CRITICALLY—use appropriate equivalents
8Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Previously discussed in Chapter 6 Cannot be applied in apothecary or
household systems Smaller to larger—move decimal to left
350 mg = 0.35 g
Larger to smaller—move decimal to right
0.850 L = 850 mL
9Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Refer to Chapter 41. State known equivalent first
(memorized)2. Add incomplete ratio on other side of
equals sign—both sides mirrored › Example: mg : g = mg : g (L:R as L:R)
3. Label all terms in the proportion, including x, when problem is first set up
10Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
4. Solve the problem using the principles of ratio and proportion
› Product of the means = product of the extremes
5. Final answer for x should be labeled with correct unit of measure
Note: Carry division at least two decimal places to ensure accuracy
11Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
8 mg = ____ g1,000 mg : 1 g = 8 mg : g
(known equivalent) (unknown)1,000 = 8
1,000 8 =
1,000 1,000 = 0.008 g
x
x
x
x
12Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
1,000 8 =
1 1,000 8
= 1,000 1,000
= 0.008 g
mg mgg x g
x
x
13Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
All measurements must be in the same system
Movement of decimals is limited to metric
› 0.6 mg = ____ mcg 0.600 mg = 600 mcg
14Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Dimensional Analysis› Used in chemistry and other sciences
Steps1.Identify the unit to which you are converting2.Write down conversion factor with desired
unit in denominator, and write the next numerator to match the previous denominator unit of measure
3.Cancel the alternate denominator/numerator units to leave the desired unit (being calculated)
4.Perform the mathematics
15Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
0.12 kg to g (both metric)1,000 g
g = 0.12 kg1 kg
1,000 gCancel the units: g = 0.12 kg
1 kg1,000 0.12 = 120 g
= 120 g
x
x
x
16Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Larger to smaller› Multiply by the conversion factor
(apothecary) (metric) gr 1/100 = ____ mg (large) (small)
› Equivalent: gr 1 = 60 mg Conversion factor = 60
› Multiply 1/100 by 60—convert to decimal› Answer: 0.6 mg
17Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Smaller to larger› Divide by the conversion factor
(metric) (apothecary) 150 mg = gr ____
(small) (large)
› Equivalent: gr 1 = 60 mg Conversion factor = 60
› Divide 150 by 60 – convert to fraction› Answer: gr 2½
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Conversion Factor Method: pounds to kg› Divide by the conversion factor
(apothecary) (metric) 110 lb = ____ kg
(small) (large)
› Equivalent: 1 kg = 2.2 lb (Conversion factor = 2.2)
› Divide 110 by 2.2 › Answer: 50 kg
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Ratio and Proportion: pounds to kg
1 kg : 2.2 lb = kg : 110 lb2.2 110
= 2.2 2.2
50 kg
x
x
x
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Abbreviated as I&O Used to monitor fluids consumed,
injected, and excreted Includes intake of “pseudo” solids that
become liquid at room temperature—Jello, popsicles
Includes liquids that exit the body—diarrhea, urine, vomitus, gastric suction, chest drainage
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Preferred method is milliliters (mL) NOT cc
May require conversion—household to metric
Recorded during the hour within which the fluid is consumed, injected, or excreted
Totaled every 24 hours
22Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
I&O record usually has key for conversions (e.g., 6 oz coffee cup = 180 mL)
After conversions, items are added for totals
1/3 glass apple juice (1 glass = 6 oz) = 60 mL1/2 cup coffee (1 cup = 8 oz) = 120 mL1/2 pint milk (1 pint = 500 mL) = 250 mL
430 mL
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Figure 8-1 Sample I&O flow sheet
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Record intravenous (IV) fluid intake Method of recording varies with
institutions Urine is sometimes recorded hourly
› Adult hourly output should be 30 mL or more
› To find average, add up total urine and divide by number of hours being recorded
Check institution policies to comply with charting requirements on I&O record