1
CON ROUNDING RULES:
Calculate one decimal place beyond the desired place
Standardization: Conversions must be standardized consistent with med math textbook
Rounding Rules related to volumes:
milliliter - when preparing oral liquids or injectables:
less than 1 milliliter round to the hundredth
greater than 1 milliliter round to the tenth
milliliter - when administering IV infusions & TF including with IV pumps & TF pumps: round to the
whole number
Rounding rules if calculating ounce, kilogram, microgram, milligram, gram, units and milliequivalents:
Ounces: Do not round
Kilograms: Always round to the tenth
Micrograms: round to the whole number
Milligrams, grams, units, milliequivalents:
Less than 1 round to the thousandth
1-10 round to the tenth
Greater than 10 - round to the whole number
Intravenous & tube feedings solution must be administered using a whole number
Round drops per minute using the standard rounding rules
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Content review: The Nurse, The Math, The Meds, by S.J. Turner, 4th edition, copyright 2019
Questions 1-3 – study and practice questions on pages 306-312
Question 4 – study and practice questions on pages 352-355
Question 5 – study and practice questions on pages 348-352
Question 6 – study and practice questions on pages 176 – 182
Question 7 – study page 163
Question 8 – study and practice questions on pages 363-368
Questions 9 – 10 – study and practice questions on pages 153 - 155
1. Ordered: IV D5W 1000 mL at 125 mL per hour
Drop factor (DF): 10 (10 drops per mL)
The nurse will set the flow rate for how many drops per minute (min)?
Drops/minute = 10 drops/1mL X 125mL/1hr X1hr/60min = 125drops/6min = 20.83 drops per minute
rounded to 21 drops per minute
2. Ordered: IV Normal Saline (NS) 500 mL at 100 mL per hour
Drop factor (DF): 60 (60 drops per mL)
The nurse will set the flow rate for how many drops per minute (min)?
2
Drops/minute = 60 drops/1mL X 100mL/1hrX1hr/60min = 100 drops per minute
3. Ordered: Packed Red Blood cells one unit (250mL) to infuse over 2 hours
Drop factor of blood tubing: 15 (15 drops per mL)
The nurse will set the flow rate for how many drops per minute (min)?
Drops/minute = 15drops/1mLX125mL/1hrX1hr/60min = 125drops/4min = 31.25 drops per minute
rounded to 31 drops per minute
4. Ordered: Isuprel (isoproterenol hydrochloride) IV infusion, 0.2 mcg per kg per minute for 12 hours
Available: isoproterenol hydrochloride 1mg in 250mL D5W
Patient’s weight: 50 kg
What flow rate (mL per hour) should be set on the infusion pump to deliver the desired dose?
mL/hour = 250mL/1mg X 1mg/1000mcg X 0.2/kg X min X 50kg/1 X 60min/1hr = 150mL/hour
5. Ordered: Lidocaine 2 mg/minute IV infusion
Available: 1 gram lidocaine in 500 mL of D5W
What will the flow rate be in mL per hour?
mL/hr = 500mL/1000mg X 2mg/1min X 60 min/ 1hr = 120/2 = 60 mL/hour
6. Ordered: 20 mg four times daily of medication for a pediatric patient
Child’s weight: 44 pounds
SDR (safe dose range) in literature: 2 to 4 mg/kg/day
Is the ordered dose in the safe dose range for this patient?
SDR = 40-80mg daily, ordered dose = 80mg daily, yes – ordered dose in the safe dose range
44 pounds/2.2 = 20 kg
2mgX 20kg = 40mg daily
4mg X 20kg = 80mg daily
Ordered dose = 20X4 = 80mg daily
7. Prozac (fluoxetine hydrochloride) 60 mg is ordered for the patient with depression.
Available: fluoxetine hydrochloride 20mg per 5 mL
How many milliliters (mL) should the nurse administer?
3
mL/dose = 5mL/20mg X 60mg/dose = 15mL/1dose = 15mL
8. Ordered: Valium (diazepam) 20 mg IV push
Available: diazepam injection 10mg/2mL
Directions: give undiluted, rate of injection is 5 mg per minute
How many minutes will be needed to administer the ordered dose?
4 minutes
mL/dose = 2mL/10mg X 20mg/dose = 4mL/1 = 4mL per dose
injection rate = 5 mg per minute, 5 mg in 1mL, so 1mL per minute
4mL needed; total time for injection is 4 minutes
9. Ordered: Zyloprim (allopurinol) 0.1 grams by mouth daily in the AM.
Available: 100 mg per tablet
How many tablets should the nurse administer?
Tab/dose = 1tab/100mg X 1000mg/1g X 0.1g/dose = 1tab/dose = 1 tablet
10. Ordered: Cipro (ciprofloxacin hydrochloride) 0.5 grams by mouth every 12 hours.
Available: 250 mg per tablet
How many tablets should the nurse administer for the AM dose?
Tab/dose = 1tab/250mg X 1000mg/1g X 0.5g/dose = 2tab/dose = 2 tablets