A patient weighing 80 kg has to be administered dopamine as an intravenous infusion through a Micro-drip set at the rate of 10 micrograms/kg/minute. 400 milligrams of dopamine is mixed in 500 ml of Normal saline. If 60 Microdrops = 1 millilitre, the calculated drop rate will be

1. A

   30 Microdrops/minute

2. B

   60 Microdrops/minute

3. C

   90 Microdrops/minute

4. D

   120 Microdrops/minute

Appeared in: GMCH - 2015

Explanation

• The calculation correctly determines the required infusion rate based on the patient's weight and the prescribed dose.
• First, the total required dose is calculated as 800 mcg/minute (80 kg × 10 mcg/kg/min).
• Next, the concentration of the solution is found to be 800 mcg/mL (400,000 mcg in 500 mL).
• Dividing the required dose by the concentration gives a flow rate of 1 mL/minute (800 mcg/min ÷ 800 mcg/mL).
• Finally, multiplying the flow rate by the microdrip factor (60 gtt/mL) results in a drip rate of 60 microdrops/minute.

Why Other Options Were Wrong

• Option A: This rate is half of the correct rate. It would be correct if the prescribed dose was 5 mcg/kg/min, not 10 mcg/kg/min.
• Option C: This rate is 1.5 times the correct rate. It would be correct if the prescribed dose was 15 mcg/kg/min.
• Option D: This rate is double the correct rate. It would be correct if the prescribed dose was 20 mcg/kg/min.

Related Visual

Clinical Relevance

• Nursing practice connection: Use the key finding related to IV drug calculation for a weight-based medication to guide bedside assessment, documentation, and the next nursing action.
• Accurate calculation of vasoactive drugs like dopamine is critical for patient safety. Small errors in dosage can lead to severe hemodynamic instability, including dangerous hypertension, tachycardia, or arrhythmias.
• Always use an infusion pump for potent medications when available. If not, a microdrip set is essential for precise manual control, as it allows for finer adjustments compared to a macrodrip set.
• What if the nurse used a macrodrip set with a drop factor of 15 gtt/mL by mistake? The drip rate would be 1 mL/min × 15 gtt/mL = 15 drops/minute. This highlights the importance of verifying the IV tubing's drop factor before starting an infusion.

How to Approach the Question

• This is an analytical, calculation-based question. The goal is to find the final drip rate.
• First, identify all the given values: patient weight (80 kg), dose (10 mcg/kg/min), drug amount (400 mg), fluid volume (500 mL), and drop factor (60 gtt/mL).
• Follow a systematic, step-by-step approach. Start by calculating the total dose needed per minute.
• Next, determine the concentration of the drug in the IV bag (mcg per mL). Ensure all units are consistent (e.g., convert mg to mcg).
• Use the total dose and concentration to find the required flow rate in mL per minute.
• Finally, use the flow rate and the given drop factor to calculate the final answer in drops per minute.

Concept Tested & Keywords

• Concept Tested: IV drug calculation for a weight-based medication.
• Stem keywords: dopamine, intravenous infusion, Micro-drip set, 10 micrograms/kg/minute, 80 kg, 400 milligrams, 500 ml, 60 Microdrops = 1 millilitre
• Lead-in keywords: calculated drop rate

Question ID

QkOq2gskrxET6nt3h90ulR

Copy ID

Reference Book

E6 Pharmacology Nurses Shanbhag 3e pp. 56-58, 54-56