What is the recommended milrinone (phosphodiesterase inhibitor) infusion protocol for a 50 kg female patient with heart failure and a reduced ejection fraction (EF) of 30%?

Milrinone Infusion Protocol for a 50 kg Female with Heart Failure (EF 30%)

The recommended milrinone protocol for this patient is a loading dose of 50 mcg/kg (2.5 mL) administered slowly over 10 minutes, followed by a continuous infusion of 0.5 mcg/kg/min (7.5 mL/hour using a 200 mcg/mL concentration). 1

Initial Dosing Calculation

Loading Dose:

• 50 mcg/kg × 50 kg = 2,500 mcg (2.5 mL of 1 mg/mL concentration)
• Administer over 10 minutes 1
• May be given undiluted or diluted to 10 mL for easier visualization of infusion rate

Maintenance Infusion:

• Standard dose: 0.5 mcg/kg/min 1
• For a 50 kg patient: 0.5 mcg/kg/min × 50 kg = 25 mcg/min
• Using 200 mcg/mL concentration: 7.5 mL/hour infusion rate

Preparation and Administration

1. Dilute milrinone to achieve 200 mcg/mL concentration:

   • Use 10 mL of milrinone (1 mg/mL) + 40 mL diluent = 50 mL total volume 1
   • Compatible diluents: 0.45% NaCl, 0.9% NaCl, or 5% Dextrose 1

2. Administer via a secure IV line using a calibrated electronic infusion device

3. Titration range:

   • Minimum: 0.375 mcg/kg/min (5.6 mL/hr for 50 kg patient)
   • Maximum: 0.75 mcg/kg/min (11.3 mL/hr for 50 kg patient) 1

Monitoring Requirements

1. Continuous hemodynamic monitoring during infusion 2

   • Blood pressure (risk of hypotension)
   • Heart rate (risk of arrhythmias)
   • ECG monitoring (due to arrhythmogenic potential) 2, 3

2. Laboratory monitoring:

   • Daily electrolytes, BUN, creatinine 4
   • Platelet count (risk of thrombocytopenia) 2

3. Clinical response assessment:

   • Improvement in signs/symptoms of heart failure
   • Expected hemodynamic effects: 28-38% increase in cardiac index and 24-28% decrease in pulmonary capillary wedge pressure 2, 5

Dose Adjustments

Renal Function Considerations

Since milrinone is primarily excreted by the kidneys, dose adjustment is necessary for renal impairment:

Creatinine Clearance (mL/min/1.73m²)	Recommended Infusion Rate (mcg/kg/min)
5	0.2
10	0.23
20	0.28
30	0.33
40	0.38
50	0.43

Hemodynamic Response

• Titrate dose based on hemodynamic response
• If hypotension occurs, reduce infusion rate
• Maximum daily dose should not exceed 1.13 mg/kg/day 1

Duration of Therapy

• Duration depends on patient responsiveness
• Effects typically persist for 1-2 hours after discontinuation 2
• Gradual tapering is essential to prevent hemodynamic deterioration 2

Special Considerations

1. Milrinone maintains effectiveness during beta-blocker therapy and causes less tachycardia than dobutamine, making it suitable for patients on beta-blockers 2

2. Potential adverse effects to monitor:

   • Hypotension (most common)
   • Ventricular arrhythmias
   • Thrombocytopenia 2, 3

3. Contraindications:

   • Severe aortic or pulmonic valvular disease
   • Acute myocardial infarction

4. Caution in patients with coronary artery disease due to potential increased medium-term mortality 2

This protocol provides a structured approach to milrinone administration for this 50 kg female patient with heart failure and reduced ejection fraction, with appropriate dosing, monitoring, and adjustment parameters to optimize outcomes while minimizing risks.