A critical care nurse is managing a client with severe decompensated heart failure. The cl… — NCLEX-RN

A critical care nurse is managing a client with severe decompensated heart failure. The client has an admission weight of $184.8 \text{ lbs}$ .

The provider's prescription reads:
- Initiate dobutamine continuous IV infusion at $2.5 \text{ mcg/kg/min}$ .
- Titrate upward by $2.5 \text{ mcg/kg/min}$ every $15 \text{ minutes}$ until mean arterial pressure (MAP) $> 65 \text{ mm Hg}$ , up to a maximum dose of $20 \text{ mcg/kg/min}$ .

The pharmacy dispenses a customized dobutamine solution containing $1,000 \text{ mg}$ of dobutamine in $250 \text{ mL}$ of $5\%$ dextrose in water (D5W). A dedicated central venous catheter port is used for the infusion, alongside a separate line of $0.9\%$ sodium chloride running at $20 \text{ mL/hr}$ .

After initiating the infusion, the nurse performs exactly three upward titrations over the next $45 \text{ minutes}$ before the client's MAP stabilizes at $72 \text{ mm Hg}$ .

What is the dobutamine infusion pump rate in $\text{mL/hr}$ at this effective dose? (Record your answer to the nearest tenth.)

Cevap: 12.6 mL/hr

Cevap

The current dobutamine infusion pump rate is

12.6 \text{ mL/hr}

The client's weight of

184.8 \text{ lbs}

converts to

84 \text{ kg}

. The initial dobutamine dose of

2.5 \text{ mcg/kg/min}

was titrated upward three times by increments of

2.5 \text{ mcg/kg/min}

, bringing the final effective dose to

10 \text{ mcg/kg/min}

. Multiplying this dose by the client's weight (

84 \text{ kg}

) yields a total of

840 \text{ mcg/min}

, which equals

50,400 \text{ mcg/hr}

when multiplied by

60 \text{ minutes}

. Converting this hourly dose to milligrams (

50,400 \div 1,000

) gives

50.4 \text{ mg/hr}

. The pharmacy provided a concentration of

1,000 \text{ mg}

250 \text{ mL}

, meaning the solution has

4 \text{ mg}

of dobutamine per

1 \text{ mL}

. Dividing the required hourly dose (

50.4 \text{ mg/hr}

) by the concentration (

4 \text{ mg/mL}

) yields the correct infusion pump rate of

12.6 \text{ mL/hr}

Adım Adım Çözüm

Convert the client's weight from pounds to kilograms.

84 \text{ kg}

Critical care weight-based medication dosages are always calculated using the client's weight in kilograms (

184.8 \div 2.2 = 84

Determine the final dobutamine dosage after the three upward titrations.

10 \text{ mcg/kg/min}

The protocol started at

2.5 \text{ mcg/kg/min}

and was increased three times by

2.5 \text{ mcg/kg/min}

each time. Total dose =

2.5 + (3 \times 2.5) = 10 \text{ mcg/kg/min}

Calculate the total required dose in micrograms per minute.

840 \text{ mcg/min}

Multiplying the weight-based dose by the client's actual weight in kilograms determines the exact per-minute requirement (

10 \text{ mcg/kg/min} \times 84 \text{ kg} = 840 \text{ mcg/min}

Convert the per-minute dosage to an hourly dosage.

50,400 \text{ mcg/hr}

Intravenous infusion pumps are programmed in mL per hour, requiring the medication dose to be scaled to an hourly rate (

840 \text{ mcg/min} \times 60 \text{ min/hr} = 50,400 \text{ mcg/hr}

Determine the concentration of the dobutamine solution provided by the pharmacy.

4,000 \text{ mcg/mL}

(or

4 \text{ mg/mL}

)

The IV bag contains

1,000 \text{ mg}

250 \text{ mL}

, which simplifies to

4 \text{ mg/mL}

. To match the hourly dose units, convert mg to mcg:

4 \text{ mg/mL} \times 1,000 \text{ mcg/mg} = 4,000 \text{ mcg/mL}

Calculate the final infusion pump rate in mL/hr.

12.6 \text{ mL/hr}

Dividing the total hourly dose by the fluid concentration yields the volume required per hour (

50,400 \text{ mcg/hr} \div 4,000 \text{ mcg/mL} = 12.6 \text{ mL/hr}

Anahtar Kavram

Advanced parenteral medication titration and complex weight-based dose calculation

Alternatif Yöntem

Using dimensional analysis to solve in a single equation:

\frac{10 \text{ mcg}}{\text{kg} \cdot \text{min}} \times \frac{84 \text{ kg}}{1} \times \frac{60 \text{ min}}{1 \text{ hr}} \times \frac{1 \text{ mg}}{1,000 \text{ mcg}} \times \frac{250 \text{ mL}}{1,000 \text{ mg}} = 12.6 \text{ mL/hr}

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