Introduction to Drug Measures

Transcription

1 SECTION 2 Introduction to Drug Measures CHAPTER 4 Metric/International (SI) System CHAPTER 5 Unit, Percentage, Milliequivalent, Ratio, Household, and Apothecary Measures

2 36 SECTION 2 INTRODUCTION TO DRUG MEASURES CHAPTER 4 Metric/International (SI) System Objectives The learner will: 1. list the commonly used units of measure in the metric system. 2. express metric weights and volumes using correct symbols and notation rules. 3. convert metric weights and volumes within the system. Suggested Review Questions 1. What are the metric measures for length, volume, and weight and the abbreviation for each? 2. Identify each of the metric units of measure for length and the abbreviation for each. 3. Identify each of the metric units of measure for volume and the abbreviation for each. 4. Identify each metric unit of measure for weight and the abbreviation for each. 5. List the rules for correct notation of metric quantities. 6. Explain the rules for converting between larger and smaller metric units of measure. 7. List four safety rules to prevent errors when working with metric dosages. Answers to Review Questions 1. The metric measure for length is meter (m), for volume is liter (L), and for weight is gram (g). 2. The metric units for length with related value are a. A kilometer is larger than a meter; 1 kilometer = 1000 meters = inches. The acceptable abbreviation is km. b. Centimeter and millimeter are smaller than a meter; 1 centimeter = 1/100 of a meter (0.01) = inches; 1 millimeter = 1/1000 of a meter (0.001). c. Mention the fact that the metric measures for length are not commonly used in medication administration. However, centimeter and millimeter are the units of measure used in medical terminology.

3 CHAPTER 4 METRIC/INTERNATIONAL (SI) SYSTEM The metric units for volume with related value are a. A kiloliter is larger than a liter; 1 kiloliter = 1000 liters. The acceptable abbreviation is kl. b. A milliliter is smaller than a liter; 1 milliliter = liter; therefore, 1000 milliliters = 1 liter. The acceptable abbreviation is ml. c. Stress that when using any abbreviation or notation for liter, the L remains capitalized. 4. The metric units for weight with related value are a. A kilogram is larger than a gram; 1 kilogram = 1000 grams. The acceptable abbreviation is kg. b. A milligram is smaller than a gram; 1 milligram = gram. Therefore, 1000 milligrams = 1 gram. The acceptable abbreviation for milligram is mg. c. A microgram is the smallest metric unit measure for weight. A microgram is smaller than a milligram; 1 microgram = of a gram or of a milligram. Therefore, 1,000,000 micrograms = 1 gram; 1000 micrograms = 1 milligram. The acceptable abbreviation is mcg. 5. Rules for correct notation of metric quantities a. The quantity is always written in Arabic numerals. b. The numerals representing the quantity are always placed in front of the abbreviation. c. A space is placed between the numeral and unit abbreviation. d. Fractional parts of a unit are expressed as decimal fractions. e. A zero is placed in front of the decimal when it is not preceded by a whole number to emphasize the decimal point. f. Excess zeros following a decimal fraction are eliminated. (Note: This is the same format for the correct notation of numbers with decimals discussed in Chapter 1.) 6. Since there is a variation of 1000 between levels of measure in the metric system, conversion between metric units is done by moving the decimal three spaces to the left or right. Therefore, when converting equal quantities from a larger to smaller unit of measure (converting down), move the decimal three spaces to the right; when converting equal quantities from a smaller to larger unit of measure (converting up), move the decimal three spaces to the left. Suggest learners use down-right and up-left as a means to remember this conversion.

4 38 SECTION 2 INTRODUCTION TO DRUG MEASURES 7. Common errors that occur when working with metric dosages involve the transcription, calculation, or conversion between units of measure. Common problem areas and rules related to reducing the possibility of errors when working with metric dosages are a. Interpretation and transcription of medication orders (1) Fractional dosages in the metric system must be transcribed with a zero in front of the decimal point to identify its fractional value. (2) Unnecessary zeros must be eliminated when metric dosages are transcribed. b. Calculations involving decimal fractions and conversions within the metric system. A related rule is (1) Question answers to calculations that seem unreasonably large or small. (2) Conversions between g, mg, and mcg units of measure in metric dosages require moving the decimal three places. Stress rule described in question 6.

5 CHAPTER 4 METRIC/INTERNATIONAL (SI) SYSTEM 39 Name Date Chapter 4: Metric/International (SI) System Additional Practice Problems Convert the values given between the specified metric measure. 1. Convert 10 mg to mcg to g 2. Convert 2500 ml to L 3. Convert 150 mg to mcg to g 4. Convert 0.25 L to ml 5. Convert 4.5 L to ml 6. Convert 200 mcg to mg 7. Convert 10 kg to g 8. Convert 750 ml to L 9. Convert 5 mg to mcg to g 10. Convert g to mg 11. Convert 5.25 L to ml 12. Convert 0.03 mg to mcg 13. Convert 40 mcg to mg 14. Convert 100 ml to L 15. Convert 3.2 g to mg 2010 Cengage Learning. All Rights Reserved. Permission to reproduce granted for classroom use only.

6 40 SECTION 2 INTRODUCTION TO DRUG MEASURES Use official metric abbreviation and notation rules to express the following phrases as numerals. 16. Seventy-five milligrams = 17. Eight and two-tenths milliliters = 18. One thousand seven hundred fifty kilograms = 19. Eighteen micrograms = 20. Fifteen grams = 2010 Cengage Learning. All Rights Reserved. Permission to reproduce granted for classroom use only.

7 CHAPTER 4 METRIC/INTERNATIONAL (SI) SYSTEM 41 Solutions to Additional Practice Problems Convert the values given between the specified metric measure. The conversion of all values below is accomplished by moving the decimal three places to the right when converting from a larger to smaller value or three places to the left when converting from smaller to larger value. The direction of the arrows below indicates the direction of movement for the decimal places and, thus, the decimal point. Zeros are placed in front of decimals when not preceded by a whole number and trailing zeros are removed as noted in the answers below mg = mcg = 10,000 mcg 10 mg =.010. g = 0.01 g ml = L = 2.5 L mg = mcg = 150,000 mcg 150 mg =.150. g = 0.15 g L = ml = 250 ml L = ml = 4500 ml mcg =.200. mg = 0.2 mg kg = g = 10,000 g ml =.750. L = 0.75 L 9. 5 mg = mcg = 5,000 mcg 5 mg =.005. g = g g = mg = 82 mg

8 42 SECTION 2 INTRODUCTION TO DRUG MEASURES L = ml = 5250 ml mg = mcg = 30 mcg mcg =.040. mg = 0.04 mg ml =.100. L = 0.1 L g = mg = 3200 mg Use official metric abbreviation and notation rules to express the following phrases as numerals mg ml kg mcg g