CSPT - Compounded Sterile Preparation Technician Sterile Compounding Calculations Questions and Answers 2 — Questions and Answers
Question 1: A physician orders 1,000 mL of D5W with 20 mEq of potassium chloride to infuse at 125 mL/hr. How long will the infusion take?
- 6 hours
- 8 hours (Correct answer)
- 10 hours
- 12 hours
Correct answer: 8 hours
1,000 mL divided by 125 mL/hr equals 8 hours.
Infusion time equals Total Volume divided by Flow Rate. The potassium chloride additive adds negligible volume and is generally not factored into the time calculation.
Question 2: How many milligrams of vancomycin are in 200 mL of a 5 mg/mL solution?
- 100 mg
- 500 mg
- 1,000 mg (Correct answer)
- 2,000 mg
Correct answer: 1,000 mg
5 mg/mL times 200 mL equals 1,000 mg.
This fundamental calculation is used constantly in sterile compounding. Understanding this relationship allows conversion between dose, concentration, and volume.
Question 3: A 70-kg patient requires dopamine at 5 mcg/kg/min. The concentration is 400 mg in 250 mL D5W. What is the infusion rate?
- 6.6 mL/hr
- 13.1 mL/hr (Correct answer)
- 26.3 mL/hr
- 52.5 mL/hr
Correct answer: 13.1 mL/hr
Dose is 350 mcg/min. Concentration is 1,600 mcg/mL. Rate equals 350 divided by 1,600 times 60 equals 13.1 mL/hr.
Weight-based infusion calculations require multiple steps: calculate dose per minute, convert concentration to matching units, calculate rate in mL/min, then convert to mL/hr.
Question 4: What is the final concentration in percent (w/v) of 5 g of dextrose in 100 mL?
- 0.5%
- 5% (Correct answer)
- 50%
- 0.05%
Correct answer: 5%
Percent w/v equals grams per 100 mL, so 5 g per 100 mL equals 5%.
This means 50 mg/mL. Common IV solutions: D5W is 5% dextrose (50 mg/mL), NS is 0.9% sodium chloride (9 mg/mL).
Question 5: Ampicillin 500 mg IV every 6 hours for 24 hours. How many total milligrams are needed?
- 500 mg
- 1,000 mg
- 1,500 mg
- 2,000 mg (Correct answer)
Correct answer: 2,000 mg
24 hours divided by 6 hours equals 4 doses. 500 mg times 4 equals 2,000 mg.
This calculation is essential for inventory management and compounding planning. It also helps verify dosage is within the normal range for the patient.
Question 6: Using alligation, how many mL of 70% dextrose and 5% dextrose are needed for 1,000 mL of 20% dextrose?
- 231 mL of 70% and 769 mL of 5% (Correct answer)
- 500 mL of each
- 300 mL of 70% and 700 mL of 5%
- 150 mL of 70% and 850 mL of 5%
Correct answer: 231 mL of 70% and 769 mL of 5%
Using alligation: 15 parts of 70% and 50 parts of 5%. Total 65 parts. 70% needed: 15/65 times 1,000 equals 231 mL. 5% needed: 769 mL.
Alligation is a method for determining proportions of two concentrations to achieve a desired intermediate concentration. Verification: (231 times 0.70) plus (769 times 0.05) equals approximately 200 g in 1,000 mL equals 20%.
CSPT - Compounded Sterile Preparation Technician Sterile Compounding Calculations Questions and Answers 2
A physician orders 1,000 mL of D5W with 20 mEq of potassium chloride to infuse at 125 mL/hr.
How long will the infusion take?