What inotrope to use during weaning from extracorporeal (cardiopulmonary bypass) after coronary artery bypass grafting (CABG) and mitral valve replacement with elevated pulmonary artery pressures (PAPs)?

From the Guidelines

For weaning from cardiopulmonary bypass after CABG and mitral valve replacement with elevated pulmonary artery pressures, dobutamine is the preferred inotrope, as it has a neutral or beneficial effect on pulmonary vascular resistance (PVR) 1. The recommended dosing is starting at 2-5 μg/kg/min. Dobutamine offers several advantages in this clinical scenario as it provides positive inotropic support while maintaining or reducing PVR. This action helps improve right ventricular function and facilitates left ventricular filling.

• Key considerations for inotrope selection in this context include:
  • Maintaining systemic vascular resistance (SVR) greater than pulmonary vascular resistance (PVR) to avoid right ventricular ischemia 1
  • Using inotropes with neutral or beneficial effects on PVR, such as dobutamine, milrinone, or epinephrine 1
  • Avoiding sudden decreases in SVR, which can lead to right ventricular ischemia 1
• Additional therapeutic options may include:
  • Inhaled nitric oxide (iNO) at 20 parts per million to decrease PVR and improve cardiac output, particularly in patients with severe pulmonary hypertension 1
  • Phosphodiesterase inhibitors, such as milrinone, as replacement therapy after weaning from iNO 1
  • Vasopressin to maintain adequate SVR, particularly in patients with septic or liver disease 1
• Continuous monitoring of hemodynamic parameters, including cardiac output, mixed venous oxygen saturation, and pulmonary artery pressures, is essential during the weaning process to guide therapy adjustments 1.

From the FDA Drug Label

Milrinone lactate is a positive inotrope and vasodilator, with little chronotropic activity different in structure and mode of action from either the digitalis glycosides or catecholamines Milrinone lactate, at relevant inotropic and vasorelaxant concentrations, is a selective inhibitor of peak III cAMP phosphodiesterase isozyme in cardiac and vascular muscle Clinical studies in patients with congestive heart failure have shown that milrinone lactate produces dose-related and plasma drug concentration-related increases in the maximum rate of increase of left ventricular pressure

The inotrope to use during weaning from extracorporeal bypass after coronary artery bypass grafting (CABG) and mitral valve replacement with elevated pulmonary artery pressures (PAPs) is milrinone.

• Key benefits: milrinone has inotropic and vasodilatory effects, which can help improve cardiac contractility and reduce pulmonary artery pressures.
• Therapeutic range: the therapeutic range of plasma milrinone concentrations is 100 ng/mL to 300 ng/mL 2.

From the Research

Inotrope Selection for Weaning from Extracorporeal Bypass

During coronary artery bypass grafting (CABG) and mitral valve replacement with elevated pulmonary artery pressures (PAPs), the choice of inotrope is crucial for successful weaning from extracorporeal bypass. The following points summarize the key considerations:

• Milrinone: A phosphodiesterase inhibitor that has been shown to be effective in increasing cardiac output and decreasing pulmonary capillary wedge pressure 3. It is a suitable option for patients with elevated PAPs, as it can help reduce pulmonary vascular resistance.
• Dobutamine: A beta-adrenergic agonist that can increase cardiac output and heart rate. However, it may not be as effective as milrinone in reducing pulmonary vascular resistance 4.
• Comparison of Milrinone and Dobutamine: Studies have compared the effectiveness and safety of milrinone and dobutamine in various clinical settings. One study found that milrinone was more potent in increasing cardiac output and decreasing vascular resistance, while dobutamine may be superior when vascular resistance or blood pressure is low 4. Another study found that milrinone and dobutamine had similar effectiveness and safety profiles, but with differences in adverse events 5.
• Terlipressin: A vasoconstrictor that can be used to counteract the systemic hypotension induced by milrinone. It has been shown to be effective in recovering systemic vascular hypotension without increasing pulmonary vascular resistance or mean pulmonary artery pressure 6.
• Levosimendan: A calcium sensitizer that can increase cardiac output without increasing oxygen demand. It has been compared to milrinone in patients with acute heart failure and renal dysfunction, and found to have similar effectiveness and safety profiles, but with differences in adverse events 7.

Key Considerations for Inotrope Selection

When selecting an inotrope for weaning from extracorporeal bypass, the following factors should be considered:

• Hemodynamic profile: The patient's hemodynamic profile, including cardiac output, pulmonary capillary wedge pressure, and systemic vascular resistance, should be taken into account when selecting an inotrope.
• Pulmonary artery pressures: The patient's PAPs should be considered when selecting an inotrope, as some inotropes may be more effective in reducing pulmonary vascular resistance.
• Renal function: The patient's renal function should be considered when selecting an inotrope, as some inotropes may be more effective or safer in patients with renal dysfunction.
• Adverse events: The potential adverse events associated with each inotrope should be considered, including hypotension, cardiac arrhythmias, and other complications.