Dopamine 200 mg in 250 D5W at 12 mL/hr. The patient weighs 133 pounds. What is the mcg/kg/min that the patient is receiving?
a. 1.2 mcg/kg/min b. 2.1 mcg/kg/min c. 3.6 mcg/kg/min d. 2.7 mcg/kg/min Answer: _
The Correct Answer and Explanation is :
To determine the mcg/kg/min dosage of dopamine the patient is receiving, follow these steps:
Given Data:
- Dopamine concentration: 200 mg in 250 mL D5W
- Infusion rate: 12 mL/hr
- Patient weight: 133 lbs
- 1 kg = 2.2 lbs, so 133 lbs ÷ 2.2 = 60.45 kg
Step 1: Convert Drug Concentration to mcg/mL
- 200 mg = 200,000 mcg (since 1 mg = 1,000 mcg)
- 200,000 mcg is in 250 mL, so: [
\frac{200,000 \text{ mcg}}{250 \text{ mL}} = 800 \text{ mcg/mL}
]
Step 2: Determine Drug Dosage in mcg/hr
- Infusion rate = 12 mL/hr, so: [
12 \text{ mL/hr} \times 800 \text{ mcg/mL} = 9,600 \text{ mcg/hr}
]
Step 3: Convert to mcg/kg/min
- Convert mcg/hr to mcg/min: [
\frac{9,600 \text{ mcg}}{60 \text{ min}} = 160 \text{ mcg/min}
] - Divide by patient’s weight (60.45 kg): [
\frac{160 \text{ mcg/min}}{60.45 \text{ kg}} = 2.65 \approx 2.7 \text{ mcg/kg/min}
]
Answer:
The correct answer is d. 2.7 mcg/kg/min.
Explanation:
Dopamine is commonly administered via continuous IV infusion to support blood pressure and cardiac output in critically ill patients. The calculation follows a structured approach:
- Convert the drug concentration into mcg/mL.
- Multiply by the infusion rate to determine the mcg/hr dose.
- Convert to mcg/min and then normalize per kg of body weight.
- Round to match the provided answer choices.
Ensuring accurate calculations is essential, as dopamine dosing affects heart rate and vascular resistance. Errors can lead to either inadequate perfusion or excessive vasoconstriction.