Percentages
After reviewing this chapter, you should be able to:
2. Convert percents to fractions
3. Convert percents to decimals
5. Convert decimals to percents
6. Convert fractions to percents
7. Convert fractions to ratios
Percentage is a commonly used word. Sales tax is a percentage of the sale price; a final examination is a certain percentage of the final grade; interest on a home mortgage represents a percentage of the balance owed; interest on a savings account is expressed as a percentage. Health care professionals see percentages written with medications (e.g., magnesium sulfate 50%). In addition to its use with medications, percentage is also used in the assessment of burns. The size of a burn (percentage of injured skin) is determined by using the rule of nines in an adult (Figure 5-1). The basis of the rule is that the body is divided into anatomical sections, each of which represents 9% or a multiple of 9% of the total body surface area. The total body surface area (BSA) is represented by 100%. Another method used is the age-specific burn diagram or chart. Burn size is expressed as a percentage of the total BSA. In children, age-related charts are used because their body proportions differ from those of an adult and the rule of nines cannot be applied.

Many health care providers use solutions that are expressed in percentages for external as well as internal use (e.g., hydrocortisone cream, lidocaine, and intravenous [IV] solutions).
In current practice, percentage solutions are prepared by the pharmacy, and people can purchase solutions or components of the solutions over the counter. Some institutions require nurses to prepare solutions in house (in the hospital) as well as in home care for clients being cared for at home. Understanding percentages provides the foundation for preparing and calculating dosages for medications that are ordered in percentages.
The term percent (%) means parts per hundred. A percentage is the same as a fraction in which the denominator is 100, and the numerator indicates the part of 100 that is being considered.
PERCENTAGE MEASURES
IV solutions are ordered in percentage strengths, and nurses need to be familiar with their meaning (e.g., 1,000 mL 5% dextrose and water). Percentage solution means the number of grams of solute per 100 mL of diluent.
Example 2:
250 mL IV of 10% dextrose contains 25 g (grams) of dextrose
% = g per 100 mL; therefore 10% = 10 g per 100 mL
In addition to encountering percentage strengths with IV solutions, the nurse may see percentages used with a variety of other medications, including eye and topical (for external use) ointments and creams. For example, Kenalog cream is available in 0.02%, 0.025%, 0.1%, 0.5%; and pilocarpine hydrochloride ophthalmic solution is available in 0.25%, 0.5%, 1%, 2%, up to 10%.

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