 # Math for Clinical Practice

## Presentation on theme: "Math for Clinical Practice"— Presentation transcript:

Math for Clinical Practice
Units of Measure Math for Clinical Practice

Weight Kilogram = kg Gram = g Milligram = mg Microgram = mcg

Length 1 meter = m Centimeter = cm Millimeter = mm

Volume 1 liter = L 1 milliliter = mL or cc
(cc is not to be used anymore according to JACOH standards but it is a common error since it has been used for years) CC = mL

Length 1 meter (m) = 100 cm or 1000 mm Centimeter (cm) = 10 mm
Millimeter (mm) = 0.1 cm

Household Abbreviations
1 ounce or oz Tablespoon = Tbs Teaspoon = tsp or t

Conversion of Metric Units

Household Measurement
1 ounce (oz) = 30 mL 1 tablespoon (Tbs) = 15 mL 1 teaspoon (tsp) = 5 mL

Ounces to mL You are doing intake and output and the mother states the infant has consumed 3 ½ ounces of formula. How many mL has the infant consumed? 3.5 x 30 mL = 105 mL You would record 105 mL on the intake record

Measuring Liquids

Tablespoons You are teaching a geriatric patient how to measure her medications. She is to take 15 mL of liquid Maalox to aid digestion. You would instruct her to use what household measuring device to take her mediation? Teaspoon or tablespoon She would take one tablespoon of medication.

Teaspoon You are working with a mother of a toddler and she has been instructed to give the child 1 ½ teaspoons of medication. You are demonstrating how to give the medication with a syringe with measurements in mL. How many mL would you have her give?

1 Teaspoon = 5 ml 1 ½ teaspoons = 1.5 teaspoons
1.5 teaspoon x 5 mL = 7.5 mL You would have her draw up 7.5 mL in a po syringe.

Nursing Alert Remember if there is not a number to the left of the decimal point a zero is placed there to highlight the decimal point placement. Correct: 0.5 mL or 0.25 g Incorrect: 5.0 mL or 25.0 g

Nursing Alert Decide whether you are converting from smaller unit to larger unit or larger unit to smaller unit.

Liter to milliliters 1 liter (L) = 1000 milliliters (mL)
1.2 x 1000 = 1200 mL

Milliliters (mL) to Liters (L)
Change mL to Liter (L) mL is smaller than a liter Move decimal point three places to the right 750 mL = 0.75 L

Metric Units Weight Kilogram = kg 1 kg = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg) 1 milligram (mg) = 1000 micrograms mcg

How to calculate kilograms
Remember you will weigh less in kilograms To convert pounds to kilogram you divide by 2.2 Convert 100 pounds to kg 100 / 2.2 = or 45.45 In the infant / small child carry out to the 100th or two decimal places.

Example Convert the following metric measurement: 0.2 mg = ______ g.
(gram is larger than a mg) Need to move the decimal 3 places or divide by 1000. Answer 0.2 mg = g

Example 100 mcg = ______ mg You are going from a smaller unit to a larger unit. You would move the decimal point 3 places or divide by 1000. 100 mcg = 0.1 mg

International and Milliequivalent Measures

International Units Heparin, insulin, penicillin, epoetin products (Epogen, Procrit) are measured in international units. Example: regular insulin 10 units SQ in am Example: penicillin 600,000 units IM x one dose

Milliequivalent Measures
Do not confuse with milligrams. Notation is mEq Milliequivalent measures the number of grams of equivalent weight of a drug contained in 1 mL of normal saline.

mEq Common drugs: sodium bicarbonate, sodium chloride, potassium chloride. Examples: 10 mEq of potassium chloride to ½ L of IV solution 15 mEq of sodium chloride to 1 L of IV solution

Conversions

Conversions Clinical connection: often you need to calculate between different systems of measure.

Metric System Metric System 1 kg = 1000 g 1 g = 1000 mg
1 mg = 1000 mcg 1 L = 1000 mL

Grains 60 mg = 1 gr 45 mg = ¾ gr 30 mg = ½ gr 15 mg = ¼ gr

Conversion to Metric Equivalents
60 mg gr1 45 mg Gr 3/4 gr 1/4 15 mg gr 1/2 30 mg

Practice Problems gr ¾ = ___________ mg gr ¼ = ___________ mg

Practice problems The bottle of Tylenol states that you are to give X (ten grains) of Tylenol. How many mgs are you giving ________

Chapter Review

Calculations in the Clinical Setting

Ratio – Proportion Method
Using the ratio proportion method offers a systematic approach to solving clinical math calculations.

The Set-up Solving the unknown The cookies and the eggs
If the recipe states you need 2 eggs to make 2 dozen cookies. How many eggs do you need to make a dozen cookies? 24 cookies 12 cookies 2 eggs = x eggs

Practice Problem Page 106 Lorazepram 3 mg IV every 6 hours as needed.
Lorazepam is supplied as 4 mg / mL

The set-up 4 mg 3 mg 1mL = x mL (cross multiply) 3 / 4 x = 0.75 mL
You would draw up 0.75 mL to equal 2 mg of Lorazepam

Practice Problem Page 108 Phenytoin sodium 300 mg by mouth at bedtime.
Phenytoin sodium supplied as 125 mg / 5 mL.

The Set-up 125 mg 300 mg 5 mL = x mL (Cross multiple) (X is on the bottom) 1500 125 X = 12 mL equals 300 mg of the drug

Practice Problems Remember to label properly and put the x on the bottom.

Body Weight

Review Pounds to kilograms Pounds divided by 2.3
Practice problems 1-10 page

Practice Problem Neupogen 5 mcg/kg/day IV over 30 minutes.
Patient weight = 174

Change Pounds to Kilograms
174 / 2.2 = kg

Determine the dosage 5 mcg / kg / day
5 mcg x (weight in kg) = mcg per dose Drug is rounded to 395 mcg per dose to be added to 50 mL of Dextrose 5% in Water.

Practice Problem Phenobarbital 30 – 120 mg / kg per day in 3 divided doses Physician orders the maximum dose or 120 mg / day to be given q 8 hours. 1st you would need to divide 120 mg by 3 doses = 40 mg per dose

Determine the Amount Phenobarbital is provided as 65 mg / mL
For one dose you would need to draw up how much of the medication? 40 mg = 60 mg x mL 1 mL 40 mg = mL 60 x