Worked example

Weight-based IV infusion - practice problem 2

A patient weighing 90 kg has dopamine 800 mg in 250 mL. The prescriber orders 10 mcg/kg/min.

Weight90 kg

Ordered rate10 mcg/kg/min

Bag800 mg in 250 mL

What pump rate (mL/hr) delivers this order?

Answer: 16.9 mL/hr

Step-by-step solution

1. Find the bag concentration in mcg/mL

800 mg × ( 1000 mcg ÷ 1 mg ) ÷ 250 mL

= 3200 mcg/mL

2. Dose per minute: multiply the rate by the patient's weight

10 mcg/kg/min × 90 kg

= 900 mcg/min

3. Convert to mcg per hour

900 mcg/min × ( 60 min ÷ 1 hr )

= 54000 mcg/hr

4. Divide by concentration so mcg cancels, leaving mL/hr

54000 mcg/hr × ( 1 mL ÷ 3200 mcg )

= 16.9 mL/hr