The unit of measurement is a vital aspect of understanding dosage calculations by nurses. Understanding the equivalencies between different units of measurements is crucial for accurate drug measurements and dose calculation.

Apothecary Measurement System

The apothecary measurement system comprises weight measurements like dram, ounce, grain (gr), scruple, and pound. The volume units of measurement in the apothecary measurement system are a fluid ounce, a pint, a minim, a fluid dram, a quart, and a gallon. The table below illustrates the weight and volume apothecary system measurements and their approximate equivalents:

Weight

• 1 grain (gr) = weight of a grain of wheat = 60 mg
• 1 scruple = 20 grains (gr) = 3 scruples
• 1 dram = 8 drams = 12 ounces
• 1 ounce = 30 g
• 1 pound = 16 ounces = 480 g

Volume

• 1 minim = 0.001 milliliter (mL)
• 1 centiliter (cl) = 0.01 liter
• 1 fluid dram = 8 fluid drams
• 1 fluid ounce = 16 fluid ounces
• 1 pint = 2 pints
• 1 quart = 4 quarts
• 1 gallon = 4 quarts = 8 pints = 3,785 mL

Metric Measurement System

The metric measurement system includes volume measurements such as liters (L), cubic milliliters (ml), and cubic centimeter (cc); its units of weight are kilograms (kg), grams (g), milligrams (mg), and micrograms (mcg). Here is a table displaying the metric length, volume, and weight measurements and their equivalents:

Length

• 1 millimeter (mm) = 0.001 meter
• 1 centimeter (cm) = 0.01 meter
• 1 decimeter (dm) = 0.1 meter
• 1 kilometer (km) = 1000 meters
• 10 millimeters (mm) = 1 centimeter (cm)
• 10 centimeters (cm) = 1 decimeter (dm)
• 10 decimeters (dm) = 1 meter
• 1 kilometer (km) = 1000 meters

Volume

• 1 milliliter (mL) = 1 cubic centimeter (cc)
• 1 centiliter (cl) = 10 milliliters (mL)
• 1 deciliter (dl) = 100 milliliters (mL)
• 1 liter (L) = 1000 milliliters (mL) = 1000 cubic centimeters (cc)
• 1 deciliter (dl) = 1 cubic decimeter (cc)
• 1 kiloliter (kl) = 1000 liters (L)

Weight

• 1 milligram (mg) = 0.001 gram (g)
• 1 centigram (cg) = 0.01 gram (g)
• 1 decigram (dm) = 0.1 gram (g)
• 1 kilogram (km) = 1000 grams (g) = 2.2 pounds (lbs)
• 1 pound (lb) = 453.59237 grams (g)
• 1 pound (lb) = 0.45359237 kilograms (kg)

Fractions

Understanding fractions is essential in nursing dosage calculations. There are two types of fractions: proper fractions (less than 1) and improper fractions (more than 1). Fractions are represented numerically, such as 1/2, 6/8, and 12/4, with a numerator and a denominator.

Both proper and improper fractions can be reduced to their lowest common denominator, making them more understandable and manageable for calculations.

For example, 24/56 can be reduced by dividing both the numerator and denominator by 8, resulting in 3/7.

Mixed Numbers

Mixed numbers are a combination of a whole number greater than one and a fraction. Before performing calculations using mixed numbers, they need to be converted into improper fractions. The conversion process involves multiplying the denominator of the fraction by the whole number, adding the numerator of the fraction, and placing the sum over the denominator.

For instance, the mixed number 3 2/8 can be converted into an improper fraction as (8 x 3 + 2)/8 = (24 + 2)/8 = 26/8.

Decimals

Decimals are another crucial aspect of nursing dosage calculations. They are based on our system of tens, where the decimal point indicates different place values such as tenths, hundredths, and thousandths.

For instance, 0.7 represents 7 tenths, while 8.13 represents 8 and 13 hundredths. Decimals are often rounded off in pharmacology calculations for clarity and accuracy.

Understanding these concepts of unit of measurement, fractions, mixed numbers, and decimals is essential for nurses to accurately and safely perform drug dosage calculations. Further practice problems and examples will reinforce this knowledge and improve nurses' confidence in medication administration. For a comprehensive understanding and practice, resources such as "Dosage Calculation Practice Problems with Answers PDF" and "Nursing Math Practice Worksheets with Answers" can be extremely beneficial.