Question

Difficulty: MediumPharmacological and Parenteral Therapies

A client weighing 78 kg78\text{ kg} is admitted to the progressive care unit with a hypertensive crisis. The healthcare provider prescribes a continuous intravenous infusion of sodium nitroprusside at a rate of 3 mcg/kg/min3\text{ mcg/kg/min}. The medication is supplied as sodium nitroprusside 50 mg50\text{ mg} mixed in 250 mL250\text{ mL} of 5%5\% dextrose in water (D5W). At what rate should the nurse set the infusion pump in mL/hr\text{mL/hr}? Round your answer to the nearest tenth.

Answer: 70.2 mL/hr

Answer

70.2
To determine the correct infusion pump rate, the nurse must first calculate the total hourly dose based on the client's weight (78 kg×3 mcg/kg/min×60 min/hr=14,040 mcg/hr78\text{ kg} \times 3\text{ mcg/kg/min} \times 60\text{ min/hr} = 14,040\text{ mcg/hr}). Next, this dose must be converted to match the supplied medication unit (14,040 mcg=14.04 mg14,040\text{ mcg} = 14.04\text{ mg}). Finally, dividing the hourly dose by the concentration of the IV solution (14.04 mg/hr÷0.2 mg/mL14.04\text{ mg/hr} \div 0.2\text{ mg/mL}) yields exactly 70.2 mL/hr70.2\text{ mL/hr}.

Step-by-Step Solution

1
Calculate the required dose in micrograms per minute.
234 mcg/min234\text{ mcg/min}
The prescription is weight-based, so the client's total body weight must be multiplied by the ordered rate of 3 mcg/kg/min3\text{ mcg/kg/min}.
2
Convert the minute dose to an hourly dose.
14,040 mcg/hr14,040\text{ mcg/hr}
Intravenous infusion pumps are programmed in milliliters per hour, so the total medication dose must be determined on an hourly basis.
3
Convert the hourly dose from micrograms to milligrams.
14.04 mg/hr14.04\text{ mg/hr}
The supplied medication is measured in milligrams, so units must match the supply before calculating the final volume.
4
Calculate the concentration of the supplied intravenous medication.
0.2 mg/mL0.2\text{ mg/mL}
Dividing the total drug mass (50 mg50\text{ mg}) by the total fluid volume (250 mL250\text{ mL}) yields the amount of active drug in each milliliter of solution.
5
Calculate the final pump infusion rate in mL/hr.
70.2 mL/hr70.2\text{ mL/hr}
Dividing the required hourly dose (14.04 mg/hr14.04\text{ mg/hr}) by the drug concentration (0.2 mg/mL0.2\text{ mg/mL}) determines the exact fluid volume needed per hour.

Key Concept

Weight-based continuous intravenous medication calculations
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