Order: Cefazolin 25 mg/kg/30 min IVPB for otitis media

Question

Available: 500 mg in 50 mL 0.9% NS
Drop factor: 10 gtts/mL
Client's weight: 40 lbs
Calculate the flow rate_ Show all work using dimensional analysis

Answer 1

To calculate the flow rate, we need to find the total volume of Cefazolin that needs to be infused and the time it takes to infuse that volume.

Step 1: Convert the client's weight from pounds to kilograms.
40 lbs ÷ 2.2 = 18.18 kg (rounded to two decimal places)

Step 2: Calculate the total dose of Cefazolin required.
25 mg/kg x 18.18 kg = 454.5 mg

Step 3: Calculate the total volume of the Cefazolin solution needed.
The concentration of the solution is 500 mg in 50 mL, so the concentration can be expressed as 10 mg/mL.
454.5 mg ÷ 10 mg/mL = 45.45 mL

Step 4: Calculate the flow rate.
Time = 30 minutes
Volume = 45.45 mL

Flow rate = Volume / Time
Flow rate = 45.45 mL / 30 minutes

To ensure consistent units, we convert minutes to hours:
Flow rate = 45.45 mL / 0.5 hours
Flow rate = 90.9 mL/hour

Step 5: Convert the flow rate to drops per minute.
We know that 1 mL = 10 gtts (drop factor given)

90.9 mL/hour * 10 gtts/mL = 909 gtts/hour

To ensure consistent units, we convert hours to minutes:
909 gtts/hour ÷ 60 minutes/hour = 15.15 gtts/minute (rounded to two decimal places)

The flow rate is approximately 15.15 gtts/minute.