Worked example

Weight-based IV infusion - practice problem 12

A patient weighing 50 kg has dobutamine 1000 mg in 250 mL. The prescriber orders 7.5 mcg/kg/min.

Weight50 kg

Ordered rate7.5 mcg/kg/min

Bag1000 mg in 250 mL

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

Answer: 5.6 mL/hr

Step-by-step solution

1. Find the bag concentration in mcg/mL

1000 mg × ( 1000 mcg ÷ 1 mg ) ÷ 250 mL

= 4000 mcg/mL

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

7.5 mcg/kg/min × 50 kg

= 375 mcg/min

3. Convert to mcg per hour

375 mcg/min × ( 60 min ÷ 1 hr )

= 22500 mcg/hr

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

22500 mcg/hr × ( 1 mL ÷ 4000 mcg )

= 5.6 mL/hr