Dopamine Dosing Calculation for 1kg Infant
For a 1kg infant receiving dopamine at 20 mcg/kg/min, the total dose is 20 mcg/min (or 0.02 mg/min), which is at the upper end of the recommended dosing range and requires careful monitoring for adverse effects.
Dose Calculation
- 20 mcg/kg/min × 1 kg = 20 mcg/min total dose 1
- This can also be expressed as 0.02 mg/min or 1.2 mg/hour 2
Clinical Context and Safety Considerations
Dosing Range Assessment
- The American Academy of Pediatrics recommends dopamine infusion rates of 2-20 mcg/kg/min for cardiogenic/distributive shock, titrated to desired clinical effect 1
- At 20 mcg/kg/min, this infant is at the maximum recommended dose and approaching the threshold where significant adverse effects become more likely 1
- Infusion rates of 20 mcg/kg/min may cause peripheral, renal, and splanchnic vasoconstriction and ischemia 1
Dose-Dependent Pharmacologic Effects
The effects at this dose level include 1:
- Alpha-adrenergic effects predominate at higher doses (>10-15 mcg/kg/min), causing significant vasoconstriction 1
- Low-dose effects (1-5 mcg/kg/min) on dopaminergic and beta-adrenergic receptors are minimal at this rate 1
- Risk of arrhythmias and hypertension increases substantially at doses >10 mcg/kg/min 1, 3
Critical Monitoring Requirements
At this dose, the following adverse effects must be monitored closely 1, 2:
- Tachyarrhythmias and ectopic beats - particularly concerning at doses >10 mcg/kg/min 1, 3
- Peripheral vasoconstriction leading to tissue ischemia 1
- Extravasation injury - can cause severe skin necrosis and sloughing 1, 2
- Disproportionate rise in diastolic pressure with marked decrease in pulse pressure 2
Neonatal-Specific Considerations
- Dopamine clearance in neonates averages 96.2 ± 55.4 mL/kg/min, with substantial interindividual variation 4
- The elimination half-life is approximately 2 minutes in full-term neonates and may be 4-5 minutes in preterm infants 5
- Inotropic response is diminished in neonates compared to older children due to immature norepinephrine stores 5
- Neonates with hepatic or renal dysfunction have >3-fold prolongation of dopamine clearance (25.1 ± 17.2 mL/kg/min), increasing toxicity risk 4
Practical Infusion Preparation
Using the "Rule of 6" method 1:
- 6 × body weight (kg) = mg of dopamine diluted to 100 mL saline
- For this 1kg infant: 6 mg dopamine in 100 mL = 60 mcg/mL concentration
- At 1 mL/hour infusion rate = 1 mcg/kg/min
- Therefore, 20 mL/hour = 20 mcg/kg/min 1
Alternative Concentration Options
The FDA label provides multiple concentration options 2:
- 800 mcg/mL solution - preferred when fluid expansion is not a problem 2
- 1600 mcg/mL or 3200 mcg/mL solutions - preferred in patients with fluid retention or when slower infusion rates are desired 2
Critical Clinical Pitfalls
When to Reduce or Discontinue
The dose should be decreased or temporarily suspended if 2:
- Diminution of established urine flow rate occurs
- Increasing tachycardia develops
- New dysrhythmias appear
- Disproportionate rise in diastolic pressure is observed
Discontinuation Protocol
- Gradually decrease the dopamine dose while expanding blood volume with IV fluids to prevent marked hypotension 2
- Abrupt discontinuation can lead to hemodynamic collapse 2
Infusion Safety
- Must use an infusion pump, preferably volumetric - gravity drip is inadequate 2
- Infuse into a large vein (antecubital fossa preferred) to prevent extravasation 2
- Continuously monitor infusion site for free flow 2
- Have phentolamine available (0.1-0.2 mg/kg up to 10 mg diluted in 10 mL saline) for intradermal injection if extravasation occurs 1, 2