Milrinone: Cardiac Medication Mini Series, Part One

Part one of our cardiac medication mini-series spotlights Milrinone. We’ll unpack milrinone’s mechanism of action, indications, and potential pitfalls. This high-value overview distills need-to-know details about milrinone for seasoned critical care nurses and students alike.

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What is Milrinone?

Milrinone is a powerful inotrope that provides cardiac support to patients facing acute heart failure, pulmonary hypertension, or chronic heart failure.

It is often administered in cardiac surgical procedures, such as coronary artery bypass graft surgery, cardiac transplantation, and other operations that necessitate cardiac support.

Mechanism of Action

  • Inhibits enzyme phosphodiesterase III (PDE3) in heart/blood vessel cells
  • Prevents breakdown of cyclic AMP (cAMP)
  • cAMP increases calcium influx into cells
  • More calcium causes stronger myocardial contractions and relaxation of smooth muscle
  • The dilation of blood vessels reduces vascular resistance and lowers blood pressure. This vasodilatory effect reduces the workload on the heart, making it easier for the heart to pump blood and improving overall cardiac output.


  • Milrinone is typically administered intravenously in critical care settings
  • It is used for short-term management of heart failure or as a bridge to other therapies such as LVAD or heart transplant
  • Also used off-label for pulmonary hypertension and myocarditis in pediatrics

Risks/Adverse Effects

  • Associated with arrhythmias and sudden death, especially with long-term use
  • Can cause hypotension due to blood vessel relaxation
  • Other side effects can include tachycardia, hypokalemia, and elevated liver enzymes

Nursing Considerations

  • Monitor vital signs closely, especially BP, HR, and SpO2
  • Telemetry is required to monitor for arrhythmias
  • Evaluate your patient’s fluid volume status. The improvement in cardiac output can lead to increased urine output (diuresis).