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Difficulty: MediumPharmacological and Parenteral Therapies

A healthcare provider prescribes a continuous intravenous (IV) infusion of lidocaine at 2 mg/min2\text{ mg/min} for a client exhibiting ventricular tachycardia. The pharmacy delivers an infusion bag containing 2 g2\text{ g} of lidocaine mixed in 500 mL500\text{ mL} of 5%5\% dextrose in water (D5W\text{D}_5\text{W}). What is the infusion rate in mL/hr\text{mL/hr} that should be programmed into the IV pump? (Record your answer as a whole number.)

Answer: 30 mL/hr

Answer

30
The correct infusion rate is calculated by standardizing the units of time and mass, determining the hourly milligram requirement (120 mg/hr120\text{ mg/hr}), and then using dimensional analysis or the desired-over-have method to find the volume needed for that specific dose (30 mL/hr30\text{ mL/hr}).

Step-by-Step Solution

1
Convert the prescribed rate from milligrams per minute to milligrams per hour.
2 mg/min×60 min/hr=120 mg/hr2\text{ mg/min} \times 60\text{ min/hr} = 120\text{ mg/hr}
The final requested unit is in hours (mL/hr), so the target dose must reflect an hourly rate.
2
Convert the total available medication from grams to milligrams.
2 g=2000 mg2\text{ g} = 2000\text{ mg}
To ensure correct ratio calculation, the units of the prescribed dose and the available medication must match.
3
Calculate the volume required to deliver the hourly dose.
120 mg/hr2000 mg×500 mL=30 mL/hr\frac{120\text{ mg/hr}}{2000\text{ mg}} \times 500\text{ mL} = 30\text{ mL/hr}
Using the standard formula (Desired Dose / Available Dose) \times Volume determines the correct pump setting in mL/hr.

Key Concept

Intravenous medication dosage calculation requiring unit conversion for both time and mass.
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Topics

Pharmacological and Parenteral Therapies

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