If 500 ml of normal saline is to be infused in 4 hours, then how many drops need to be infused per minute? The drop factor is 20 macro drops per ml.

1. A

   42

2. B

   46

3. C

   21

4. D

   38

Appeared in: DSSSB -28 August 2019 (Shift-2)

Explanation

• The correct formula for calculating the IV drip rate is: Flow Rate (gtt/min) = (Total Volume in mL × Drop Factor) / Time in minutes.
• First, convert the infusion time from hours to minutes: 4 hours × 60 minutes/hour = 240 minutes.
• Substitute the given values into the formula: (500 mL × 20 gtt/mL) / 240 minutes.
• Perform the calculation: 10,000 / 240 = 41.67 gtt/min.
• Since drops must be administered as whole numbers, the result is rounded to the nearest whole number, which is 42.

Why Other Options Were Wrong

• Option B: This is an incorrect value resulting from a calculation error. It does not match the output of the standard IV drip rate formula with the given parameters.
• Option C: This value is approximately half of the correct rate. This error could occur if the time was incorrectly doubled (e.g., using 480 minutes instead of 240) or if the volume was halved.
• Option D: This is an incorrect value resulting from a calculation error. It does not align with the correct formula and given values.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain IV Drip Rate Calculation as background academic context rather than a clinical decision trigger.
• Accurate IV drip rate calculation is a fundamental nursing skill critical for patient safety. It prevents under- or over-hydration and ensures medication is delivered at the prescribed rate.
• Administering fluids too quickly can lead to fluid volume overload, especially in patients with cardiac or renal compromise. Administering too slowly can delay therapeutic effects or lead to dehydration.
• What if? If the order was to infuse the same 500 mL over 8 hours instead of 4, the rate would be halved. The new rate would be (500 × 20) / 480 = 20.83, which rounds to 21 gtt/min.

How to Approach the Question

• Identify the question type: This is a calculation-based question requiring a specific formula.
• Extract the key values from the stem: Volume = 500 mL, Time = 4 hours, Drop Factor = 20 gtt/mL.
• Ensure all units are consistent for the formula. The formula requires time in minutes, so convert 4 hours to 240 minutes (4 × 60).
• Recall the standard formula: Flow Rate (gtt/min) = (Volume × Drop Factor) / Time (min).
• Substitute the values into the formula and perform the calculation: (500 × 20) / 240.
• Round the final answer to the nearest whole number, as partial drops cannot be administered.

Concept Tested & Keywords

• Concept Tested: IV Drip Rate Calculation
• Stem keywords: 500 ml, normal saline, 4 hours, drops per minute, drop factor, 20 macro drops
• Lead-in keywords: how many
• Negative lead-in flag: false

Question ID

Q7KaAt_jEACwiH8nHVk3eM

Copy ID

Reference Book

E6 Pharmacology Nurses Shanbhag 3e p. 54-56

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 93-95