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After completing this unit, you should be able to: Explain the role of the medical assistant to ensure safe dosage calculations; identify systems of measurements and their common uses; convert among systems of measurements;...
CHAPTER 52 Dosage Calculation © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-2 Learning Outcomes 52.1 Explain the role of the medical assistant to ensure safe dosage calculations 52.2 Identify systems of measurements and their common uses 52.3 Convert among systems of measurements © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-3 Learning Outcomes 52.4 Execute dosage calculations accurately 52.5 Calculate dosages based upon body weight and body surface area © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-4 Introduction • Administer medications – Close attention to detail – Dosage calculation must be accurate • Basic math • Systems of measurement • Conversions within or between measurement systems • Calculations for special patient populations © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-5 Ensuring Safe Dosage Calculations • Minor math errors major error in dosage • Each time you calculate a dosage – Analyze the problem – Estimate a range – Is the answer reasonable? © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-6 Measurement Systems • Three systems – Metric ~ most common – Apothecary – Household • Focus on the basic units of – Volume – Weight © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-7 Metric System • Based on multiples of 10 • Basic units – Volume = liter (L) – Weight = gram (g) • Prefixes indicate multiples of each © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-8 Metric System Prefix Kilo- Base unit Centi- Milli- Micro- Value Weight × 1000 kilogram -gram ÷ 100 centigram ÷ 1000 milligram ÷ 1,000,000 microgram (kg) (g) (cg) (mg) (mcg) 1000 g 1g 0.01 g 0.001 g 0.000001 g kiloliter liter centiliter milliliter microliter (kL) (L) (cL) (mL) (mcL) 1000 L 1L 0.01 L 0.001 L 0.000001 L Volume © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-9 Apothecary and Household Systems • Apothecary – Weight – Volume • Fluid ounces • Drams • Fluid drams • Ounces • Pint quart • Pounds © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-10 Apothecary and Household Systems • Household – only volume – Drops – Ounces – Teaspoons and tablespoons – Cups – Pints, quarts, and gallons © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-28 Apply Your Knowledge The physician has ordered ampicillin 500 mg, on hand 250 mg capsules How much would you give? capsules You have 50 mg metoprolol as a scored tablet on hand and the doctor tells you to give 25 mg How much would you give? ½ tablet © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part Body Weight and Body Surface Area Calculations 52-29 • More common for pediatric or geriatric dosages – Greater risk of harm – Calculations must be precise © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-30 Dosages Based on Weight • Order – Dosage of medication / weight of patient – Over a unit of time • Weight must be calculated in kilograms © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-31 Dosages Based on Weight (cont.) © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-32 Dosages Based on Weight (cont.) © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-33 Dosages Based on Weight (cont.) © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-34 Dosages Based on Weight (cont.) Calculate the amount to administer Refer to label for medication on hand © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-35 Dosages Based on Weight (cont.) © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-36 Dosages Based on Weight (cont.) © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-37 Dosages Based upon Body Surface Area • Precise dosages – Pediatric patients – Burn patients – Chemotherapy patients • Nomogram – Plot height and weight – Third scale will give the BSA © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-38 Apply Your Knowledge A 5-year-old child weighs 44 lbs The physician orders him to receive Zinacef 50 mg/kg/day IM q6h What is the child’s weight in kg? 20 kg How many milligrams of medication should the child receive in one dose? 250 mg © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-39 In Summary 52.1 A medical assistant must be proficient in math and determine if the answer to every calculation he performs is reasonable 52.2 The metric system is based on 10 and is the most common system of measurement for dosage calculations Metric units commonly used for dosage calculations include g, mg, mcg, and mL The apothecary and household systems have some equal measures, but they are used rarely © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-40 In Summary (cont.) 52.3 To convert among systems of measurements, you can refer to a conversion chart or perform a proportion method calculation Keep in mind that measurements between the metric and apothecary and household systems are only approximations © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-41 In Summary (cont.) 52.4 Use the formula method or proportion method to perform dosage calculations Formula Method D/H × Q Proportion Method D/X = H/Q 52.5 Dosages based on body weight and BSA are used when precise amounts of medication must be administered Body weight calculations are usually ordered in mg/kg/day BSA calculations use special formulas or a nomogram © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part 52-42 End of Chapter 52 Math is like love a simple idea but it can get complicated ~ Unknown © 2014 by McGraw-Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part .. .52- 2 Learning Outcomes 52. 1 Explain the role of the medical assistant to ensure safe dosage calculations 52. 2 Identify systems of measurements and their common uses 52. 3 Convert... posted on a website, in whole or part 52- 3 Learning Outcomes 52. 4 Execute dosage calculations accurately 52. 5 Calculate dosages based upon body weight and body surface area © 2014 by McGraw-Hill... or posted on a website, in whole or part 52- 5 Ensuring Safe Dosage Calculations • Minor math errors major error in dosage • Each time you calculate a dosage – Analyze the problem – Estimate a