What is the dopamine infusion rate in drops per minute for a 50kg female?

Dopamine Infusion Rate Calculation for a 50kg Female

For a 50kg female, dopamine infusion rates should be calculated using the "rule of 6" method: multiply 0.6 × 50kg = 30mg dopamine diluted to 100mL saline, where 1mL/hour delivers 0.1 mcg/kg/min, and drops per minute equals mL/hour when using a microdrop apparatus (60 drops/mL). 1

Standard Preparation Methods

Rule of 6 Method (Preferred for Pediatric/Lower Weight Patients)

• Calculation: 0.6 × 50kg = 30mg dopamine in 100mL saline 1
• Concentration: 300 mcg/mL
• Conversion: 1 mL/hour = 0.1 mcg/kg/min = 1 drop/minute (with microdrop set) 1

Standard Adult Concentration

• Alternative preparation: 400mg dopamine in 500mL D5W yields 800 mcg/mL 2
• For this concentration in a 50kg patient:
  • 2 mcg/kg/min = 100 mcg/min = 7.5 mL/hour = 7.5 drops/minute (microdrop)
  • 5 mcg/kg/min = 250 mcg/min = 18.75 mL/hour = 19 drops/minute (microdrop)
  • 10 mcg/kg/min = 500 mcg/min = 37.5 mL/hour = 38 drops/minute (microdrop)
  • 20 mcg/kg/min = 1000 mcg/min = 75 mL/hour = 75 drops/minute (microdrop) 2

Dosing Guidelines by Clinical Indication

Initial Dosing

• Start at 2-5 mcg/kg/min for most patients requiring modest increases in cardiac output and renal perfusion 3, 1, 2
• Using Rule of 6 preparation: 20-50 drops/minute 1
• Using 800 mcg/mL preparation: 7.5-19 drops/minute 2

Dose-Dependent Effects

• 2-3 mcg/kg/min: Dopaminergic receptor stimulation (renal/mesenteric vasodilation) with limited diuretic effect 3, 1
• 3-5 mcg/kg/min: β-adrenergic effects predominate (increased cardiac contractility and output) 3, 1
• 5-10 mcg/kg/min: Mixed β-adrenergic and increasing α-adrenergic effects 3, 1
• >10 mcg/kg/min: Progressive α-adrenergic stimulation with peripheral vasoconstriction 3, 1

Titration Strategy

• Increase in 5-10 mcg/kg/min increments up to 20-50 mcg/kg/min as needed for blood pressure support 2
• Maximum recommended: 20 mcg/kg/min; doses >20 mcg/kg/min risk excessive vasoconstriction 1
• More than 50% of patients respond adequately to <20 mcg/kg/min 2

Critical Safety Measures

Administration Requirements

• Use only volumetric infusion pump—gravity drip with mechanical clamps is inadequate 2
• Infuse into large vein (antecubital fossa preferred) to prevent extravasation necrosis 2
• Continuous hemodynamic monitoring including blood pressure, heart rate, and ECG is mandatory 3, 1
• Arterial line placement recommended for doses approaching upper range 1

Extravasation Management

• If extravasation occurs: Inject phentolamine 0.1-0.2 mg/kg (up to 10mg) diluted in 10mL saline intradermally at the site 1
• Watch continuously for signs of infiltration as tissue necrosis can occur 2

Important Contraindications and Cautions

• Avoid in tachycardia >100 bpm—both dopamine and dobutamine should be used cautiously 3
• Consider alternative vasopressors (norepinephrine) if inadequate response at 20 mcg/kg/min or if excessive tachycardia develops 1
• Protect solution from light using foil covering to prevent drug breakdown 1
• Do NOT add sodium bicarbonate—dopamine is inactivated in alkaline solutions 2

Discontinuation

• Gradually taper by decreasing dose in 2 mcg/kg/min increments while optimizing oral therapy 3
• Expand blood volume with IV fluids during weaning to prevent marked hypotension 2

Clinical Pearls

Time to steady state: Expect 70-125 minutes to reach 90% of plateau concentration depending on infusion rate, due to redistribution kinetics 4

Diuretic effect: At 2 mcg/kg/min, expect increased urine output (mean increase from 0.29 to 1.04 mL/kg/hr) with peak effect at approximately 7 hours, though this effect is drug-dependent and reversible 5

Pharmacodynamic variability: Individual patient response shows significant variability; plasma levels correlate with infusion rates but hemodynamic effects require individualized titration based on clinical response rather than fixed dosing 6