Measurement Systems, Basic Mathematics, and Dosage Calculations Chapter 52 Measurement Systems, Basic Mathematics, and Dosage Calculations Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. The Metric System Primary system of measurement in medicine Three basic units: Gram (g), which measures mass (weight) Liter (L), which measures volume (liquid) Meter (m), which measures length (size) Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. The Metric System Based on multiples of 10 Add prefixes to the basic units to indicate the value (multiple or submultiple) of the unit Kilo = 1000 Kilo+gram = 1000 grams Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. The Metric System Prefix Unit Decimal Value Micro- 1/1,000,000 of a unit 0.000001 Milli- 1/1,000 of a unit 0.001 Centi- 1/100 of a unit 0.01 Deci- 1/10 of a unit 0.1 No prefix 1 unit 1 Deka- 10 units 10 Hecto- 100 units 100 Kilo- 1,000 units 1,000 Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Household Measures Patients at home typically use household measurements You may need to use these measurements to explain to patients how to take their medications after discharge Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Household Measures Drop (gtt) Teaspoon (t or tsp) Tablespoon (T or tbs) Ounce (fluid) (fl oz) Cup Pint (pt) Quart (qt) Ounce (weight) (oz) Pound (lb) Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Household Measures 60 gtt = 1 tsp 3 t = 1 T 2 T = 1 fl oz 1 cup = 8 fl oz 1 pt = 2 cups 1 qt = 4 cups (2 pt) 1 lb = 16 oz Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. The Apothecary System The first system of medication measurement, but not commonly used today Basic units: Grain (gr) Quart (qt) Pint (pt) Ounce or fluid ounce (oz) Dram Minim Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Review of Basic Math Basic math skills are necessary for accurately calculating and verifying medication dosages to ensure patient safety before administering any medication Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Review of Basic Math A fraction indicates a part of a whole number Numerator: top of fraction Denominator: bottom of fraction A percentage expresses a value that is part of 100 Example >> 35% is 35/100 (or 0.35) Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Review of Basic Math A ratio expresses a relationship between two components It is another way to express a fraction Example >> 1 : 5 is the same as 1/5 Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Review of Basic Math A proportion expresses the relationship between two ratios Example >> 3 : 5 = 600 : 1000 Means: 5 and 600 Extremes: 3 and 1000 The product of the means always equals the product of the extremes You can solve for X if you know the other 3 values Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Dosage Calculations Calculating the right dose of medication is a responsibility not to be taken lightly The wrong dose of any medication can have profound adverse consequences Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Copyright ©2012 Delmar, Cengage Learning. Basic Formula (Needed/Available) x Vehicle = Dose Needed > Amount prescribed by provider Available > Supply on hand Vehicle > Form and amount of supply Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Ratio and Proportion Method Dosage on hand : amount on hand = Dosage desired : amount desired (x) When using this method, you may need to convert between units of measurement Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.

Converting Between Units of Measurement Identify the equivalent Set up a proportion of two equivalent ratios Solve for x Calculating dosage by weight Conversion factor: 1 kg = 2.2 lbs Copyright  ©2012 Delmar, Cengage Learning. All rights reserved.