Question
of the Week

Correct Answer : 13.2 mL/hr

• Explanation

Using dimensional analysis, perform the following steps to calculate the infusion rate in milliliters per hour of naloxone (NAL) diluted in normal saline (NS):

1. Identify the prescribed, available, and required medication information

   Prescribed: 2 mcg NAL / kg | hr   Available: 2 mg NAL / 2 mL   Required: mL NAL / hr

2. Identify the final diluted medication volume

   Dilution instructions: infusion bag - medication volume + medication

   OR

   500 mL NS - 2 mL NS + 2 mL NAL = 500 mL diluted NAL or 2 mg NAL / 500 mL

3. Convert the prescription to the infusion rate of NAL in milliliters per hour

   Prescription x diluted medication = mL NAL / hr

   OR

   ( mcg NAL / kg | hr ) ( kg / lb ) ( lb /   )( mg / mcg ) ( mL / mg NAL ) = mL NAL / hr

   OR

   ( 2 mcg NAL / kg / hr ) ( kg / 2.2 lb ) ( 58 lb /   )( mg / 1000 mcg ) ( 500 mL / 2 mg NAL ) = 13.1818 mL NAL / hr

4. Round to one decimal place

   13.1818 mL NAL / hr ≈ 13.2 mL NAL / hr

Educational objective:
To calculate the infusion rate of naloxone diluted in normal saline, the nurse should first identify the prescribed dose (eg, 2 mcg/kg/hr), available medication (eg, 2 mg/2 mL), and diluted volume (eg, 2 mg/500 mL) and then convert to milliliters per hour (eg, 13.2 mL/hr).

Alternate Method:

The formula method is an alternate way to calculate medication dosages. However, this method may increase the occurrence of miscalculation and medication errors. If you choose to use this method, do not round any calculations until the final step.

Using the formula method, perform the following steps to calculate the infusion rate in milliliters per hour of naloxone (NAL) diluted in normal saline (NS):

1. Convert the weight to kilograms

   ( kg / 2.2 lb ) ( 58 lb /   ) = 26.3636 kg

2. Calculate the dose in micrograms per hour

   ( 2 mcg NAL / kg | hr ) ( 26.3636 kg /   ) = 52.7272 mcg NAL / hr

3. Convert the prescription to milligrams per hour

   ( 52.7272 mcg NAL / hr ) ( mg / 1000 mcg ) = 0.0527 mg NAL / hr

4. Identify the final diluted medication volume

   Dilution instructions: infusion bag - medication volume + medication

   OR

   500 mL NS - 2 mL NS + 2 mL NAL = 500 mL diluted NAL or 2 mg NAL / 500 mL

5. Convert the prescription to the infusion rate of NAL in milliliters per hour

   Prescribed dose / diluted dose x diluted volume = mL NAL / hr

   OR

   0.0527 mg NAL / 2 mg NAL x 500 mL = 13.1818 mL NAL / hr

6. Round to one decimal place

   13.1818 mL NAL / hr ≈ 13.2 mL NAL / hr