Dosage Calculations Proctored
Exam Prep Bundle | 200 Q&A with
Rationales (Graded A+)
Question 1
,A provider prescribes an intravenous infusion of heparin at 1,400
units/hr. The pharmacy supplies a 500 mL bag containing heparin
25,000 units in 5% Dextrose in Water (\(D_{5}W\)). At what rate should
the nurse program the electronic infusion pump in mL/hr? (Round to the
nearest whole number).
VERIFIED ANSWER: 28 mL/hr
EXPLANATION: To determine the hourly infusion rate, calculate the
concentration of heparin per milliliter of fluid first:
\(\text{Concentration}=\frac{25,000\text{\ units}}{500\text{\ mL}}=50\text{\
units/mL}\)
Next, divide the prescribed hourly dose by the available
concentration:
\(\text{Infusion\ Rate}=\frac{1,400\text{\ units/hr}}{50\text{\
units/mL}}=28\text{\ mL/hr}\)
Question 2
A nurse is preparing to administer cefazolin 1.5 g IV piggyback over 45
minutes. The medication is reconstituted in a 100 mL bag of 0.9%
Normal Saline (\(0.9\%\text{ NS}\)). The nurse should program the
infusion pump to deliver how many mL/hr? (Round to the nearest whole
number).
VERIFIED ANSWER: 133 mL/hr
EXPLANATION: Calculate the hourly rate by setting up a ratio using
the total volume and total time in minutes, then converting it to
,hours (60 minutes):
\(\text{Rate}=\frac{100\text{\ mL}}{45\text{\ min}}\times 60\text{\
min/hr}=133.33\text{\ mL/hr}\)
Rounding to the nearest whole number yields 133 mL/hr.
Question 3
A critical care patient weighing 84 kg is ordered to receive a continuous
intravenous infusion of dobutamine at 7.5 mcg/kg/min. The pharmacy
provides dobutamine 500 mg pre-mixed in 250 mL of \(D_{5}W\).
Calculate the required infusion pump setting in mL/hr. (Round to the
nearest tenth).
VERIFIED ANSWER: 18.9 mL/hr
EXPLANATION: First, calculate the total required micrograms per
minute based on the patient's weight:
\(7.5\text{\ mcg/kg/min}\times 84\text{\ kg}=630\text{\ mcg/min}\)
Convert the dose to micrograms per hour:
\(630\text{\ mcg/min}\times 60\text{\ min/hr}=37,800\text{\ mcg/hr}\)
Convert micrograms to milligrams (1 mg = 1,000 mcg):
\(\frac{37,800\text{\ mcg/hr}}{1,000}=37.8\text{\ mg/hr}\)
Determine the concentration of the dobutamine bag:
\(\frac{500\text{\ mg}}{250\text{\ mL}}=2\text{\ mg/mL}\)
Divide the required mg/hr by the concentration to find the mL/hr
rate:
\(\frac{37.8\text{\ mg/hr}}{2\text{\ mg/mL}}=18.9\text{\ mL/hr}\)
, Question 4
A provider prescribes an oral liquid dose of phenobarbital 45 mg PO
twice daily for a pediatric patient. The medication container reads
phenobarbital 20 mg per 5 mL. How many mL should the nurse
administer per dose? (Round to the nearest tenth).
VERIFIED ANSWER: 11.3 mL
EXPLANATION: Utilize the standard dosage formula
(\(\frac{\text{Desired}}{\text{Have}} \times \text{Quantity}\)):
\(\text{Volume}=\frac{45\text{\ mg}}{20\text{\ mg}}\times 5\text{\
mL}=2.25\times 5\text{\ mL}=11.25\text{\ mL}\)
Rounding to the nearest tenth yields 11.3 mL.
Question 5
A patient with severe hyperkalemia is ordered to receive an intravenous
infusion of 1,000 mL of \(D_{5}W\) with insulin over 6 hours. The
gravity infusion tubing has a drop factor of 10 gtt/mL. Calculate the
necessary drip rate in gtt/min. (Round to the nearest whole number).
VERIFIED ANSWER: 28 gtt/min
EXPLANATION: Convert the total infusion time into minutes:
\(6\text{\ hours}\times 60\text{\ min/hr}=360\text{\ minutes}\)
Apply the standard drop factor calculation formula: