Dopamine Infusion Rate for a 50kg Female
For a 50kg female, the initial dopamine infusion rate should be 2-5 mcg/kg/min (100-250 mcg/min), which translates to approximately 15-38 drops per minute using a standard microdrop apparatus (60 drops/mL). 1
Preparation Using the "Rule of 6"
The most practical preparation method for this patient uses the pediatric "rule of 6" formula 1:
- 0.6 × 50 kg = 30 mg dopamine
- Dilute 30 mg to a total of 100 mL saline
- At this concentration: 1 mL/h delivers 0.1 mcg/kg/min 1
For the initial dose of 2-5 mcg/kg/min:
- Set infusion at 20-50 mL/h
- With a microdrop set (60 drops/mL): 20-50 drops per minute 1
Alternative Standard Preparation
If using the standard adult concentration of 400 mg in 500 mL D5W (800 mcg/mL) 1:
- Initial rate of 2-5 mcg/kg/min = 100-250 mcg/min for 50kg patient
- This equals 7.5-18.75 mL/h
- With microdrop apparatus: 7.5-18.75 drops per minute 2
Dose-Dependent Effects and Titration
Start at the lower end (2 mcg/kg/min) and titrate upward based on blood pressure response 1:
- 2-3 mcg/kg/min: Dopaminergic effects (renal/mesenteric vasodilation) 1
- 3-5 mcg/kg/min: β-adrenergic effects (increased cardiac contractility) 1
- >5-10 mcg/kg/min: α-adrenergic effects (peripheral vasoconstriction) 1
- Maximum: 20 mcg/kg/min (beyond this, excessive vasoconstriction occurs) 1
Critical Monitoring Requirements
Continuous hemodynamic monitoring is mandatory 1:
- Blood pressure monitoring continuously, preferably with arterial line 1
- Heart rate and ECG monitoring 1
- Assess peripheral perfusion regularly 1
- Watch for tachycardia >100 bpm, which may necessitate switching to alternative vasopressors 1
Extravasation Management
Dopamine extravasation causes severe tissue injury 1:
- Cover infusion bottle/syringe with protective foil to prevent light degradation 1
- Avoid accidental bolus injection 1
- If extravasation occurs: inject phentolamine 0.1-0.2 mg/kg (up to 10 mg) diluted in 10 mL of 0.9% sodium chloride intradermally at the site 1, 3
Important Clinical Caveats
Consider alternative vasopressors if 1:
- Dopamine doses approach or exceed 20 mcg/kg/min without adequate response
- Tachycardia develops (>100 bpm)
- Patient has marked circulatory instability or decompensated shock (epinephrine or norepinephrine may be preferable)
Steady-state plasma concentrations take 70-125 minutes to achieve, depending on infusion rate, so allow adequate time for dose titration 4. The terminal half-life ranges from 22-38 minutes 4.