NAPLEX practice question 15 of 25

If a patient is getting NS IVF at 120mls/hr, how much Sodium Chloride in grams is this patient getting in 24 hours? NS is 0.9% sodium chloride.

Full set: 154 questions

Domain Safe and Accurate Preparation, Compounding, Dispensing, and Administration of Medications and Provision of Health Care Products

Answer options
A: 25.92gm Correct answer
B: 25.92kg
C: 25.92mg
D: 90mg
E: 90gm
Correct Answer:
A. 25.92gm
Explanation

First, calculate the total volume of Normal Saline (NS) infused over 24 hours. At a rate of 120 mL/hour, the total volume is 120 mL/hr × 24 hours = 2880 mL. Normal Saline is a 0.9% w/v (weight/volume) solution of sodium chloride. This concentration means there are 0.9 grams of sodium chloride for every 100 mL of solution. To find the total grams of sodium chloride in 2880 mL, use the following calculation: (0.9 g NaCl / 100 mL) × 2880 mL = 25.92 grams of NaCl.

Why Incorrect

B. 25.92kg: The unit is kilograms (kg), which is 1000 times larger than grams. This represents a lethal overdose.
C. 25.92mg: The unit is milligrams (mg), which is 1000 times smaller than grams. This is a significant undercalculation.
D. 90mg: This value is incorrect and likely results from a miscalculation of the concentration or total volume.
E. 90gm: This value is incorrect and would be the amount of sodium chloride in 10,000 mL (10 L) of NS.

References

1. Stoklosa, M. J., & Ansel, H. C. (2013). Pharmaceutical Calculations (14th ed.). Lippincott Williams & Wilkins. Chapter 8, "Isotonic and Buffer Solutions," discusses percentage strength, and Chapter 11, "Intravenous Admixtures and Flow Rates," covers rate calculations. The principle of w/v percentage is defined as grams of constituent per 100 mL of solution.

2. University of Kentucky College of Pharmacy. (n.d.). Calculations in Pharmacy. Course materials for PGY1 Pharmacy Residency Program. Section on "IV Flow Rates and Concentrations." The materials detail the standard method for calculating total drug delivery based on infusion rate, duration, and solution concentration (e.g., % w/v).

3. Troy, D. B., & Beringer, P. (Eds.). (2006). Remington: The Science and Practice of Pharmacy (21st ed.). Lippincott Williams & Wilkins. Part 2, "Pharmaceutics," Section on "Pharmaceutical Dosage Forms and Their Delivery," provides foundational principles for parenteral preparations, including the definition of 0.9% w/v Sodium Chloride Injection, USP as containing 9 g of NaCl per 1000 mL (or 0.9 g per 100 mL).

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