250 mL of 5% dextrose contains 12,500 units of heparin. The infusion is running at 18 mL/hour. How many units of heparin are delivered per hour?

1. A

   1900 units/hour

2. B

   900 units/hour

3. C

   1800 units/hour

4. D

   300 units/hour

Appeared in: NORCET 10 Prelims-2026

Explanation

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• The calculation involves a two-step process: first, determine the concentration of the drug in units per mL.
• To find the concentration, divide the total units of heparin by the total volume of the IV fluid: 12,500 units ÷ 250 mL = 50 units/mL.
• Second, multiply this concentration by the hourly infusion rate to find the total units delivered per hour.
• The final calculation is: 50 units/mL × 18 mL/hour = 900 units/hour.

Why Other Options Were Wrong

• Option A: This value is incorrect and represents a significant overdose. It would result from an erroneous calculation or a much higher infusion rate.
• Option C: This value is double the correct dose and represents a significant calculation error. It might occur if one incorrectly multiplies the infusion rate by 100 instead of the correct concentration.
• Option D: This value is too low and represents an underdose. It would result from a calculation error or a much slower infusion rate.

Related Visual

• Visual 1: Flowchart: A step-by-step guide for IV drip rate calculation. It would visually break down the process: 1) Identify total drug and total volume. 2) Calculate concentration (Drug/Volume). 3) Identify flow rate. 4) Calculate hourly dose (Concentration x Flow Rate).
• Visual 2: Infographic: An image of an IV bag connected to an infusion pump. The IV bag would be labeled '12,500 units Heparin in 250 mL D5W'. The infusion pump screen would show 'Rate: 18 mL/hr'. An arrow would point from the pump to a clock, with the question 'Units per hour?'.

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain IV medication dosage calculation as background academic context rather than a clinical decision trigger.
• Accurate dosage calculation is a fundamental and critical nursing responsibility to ensure patient safety and prevent medication errors, especially with high-alert medications like heparin.
• Administering an incorrect dose of heparin can have severe consequences. An overdose can lead to life-threatening hemorrhage, while an underdose can fail to prevent or treat thromboembolic events, leading to complications like pulmonary embolism or deep vein thrombosis.
• What if? If the patient's latest aPTT result came back below the therapeutic range, the nurse would anticipate an order from the provider to increase the infusion rate. The nurse would then need to perform this same calculation again with the new rate to determine the new hourly dosage.

How to Approach the Question

• First, identify the question's goal: to calculate the amount of medication (in units) delivered per hour.
• Next, list all the values provided in the problem: Total units = 12,500; Total volume = 250 mL; Infusion rate = 18 mL/hour.
• Calculate the concentration of the medication in the IV solution. The formula is: Concentration = Total Amount of Drug / Total Volume.
• In this case, Concentration = 12,500 units / 250 mL = 50 units/mL.
• Now, use the concentration to find the hourly dose. The formula is: Hourly Dose = Concentration × Hourly Infusion Rate.
• Finally, calculate the answer: 50 units/mL × 18 mL/hour = 900 units/hour. The 'mL' units cancel out, leaving 'units/hour'.

Concept Tested & Keywords

• Concept Tested: IV medication dosage calculation
• Stem keywords: heparin, infusion, mL/hour, units/hour, dosage calculation
• Lead-in keywords: How many

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