What is the choice of inotropes (inotropic agents) in cardiogenic shock?

Choice of Inotropes in Cardiogenic Shock

In cardiogenic shock, dobutamine is the first-line inotropic agent, while norepinephrine is the preferred vasopressor when blood pressure support is needed. 1, 2

Definition and Diagnosis of Cardiogenic Shock

Cardiogenic shock is defined by:

• Hypotension (SBP <90 mmHg for >30 min) despite adequate filling status
• Signs of hypoperfusion (decreased mentation, cold extremities, urine output <30 mL/h, lactate >2 mmol/L)
• Hemodynamic criteria: cardiac index <2.2 L/min/m², pulmonary capillary wedge pressure >15 mmHg 1

Inotropic and Vasopressor Selection Algorithm

First-Line Agents:

• Dobutamine (2-20 μg/kg/min): First-line inotrope to increase cardiac output 1, 2
• Norepinephrine: First-line vasopressor when mean arterial pressure support is needed 1, 2

Second-Line/Alternative Agents:

• Levosimendan: Alternative or adjunct to dobutamine, especially in patients on beta-blockers 1, 2, 3
• Phosphodiesterase-3 inhibitors (milrinone): Consider especially in non-ischemic patients 1, 2

Clinical Decision-Making Based on Hemodynamic Profile

1. Low cardiac output with adequate blood pressure:

   • Start dobutamine (2-20 μg/kg/min) 2
   • Target cardiac index ≥2.2 L/min/m² and mixed venous oxygen saturation ≥70% 2

2. Low cardiac output with hypotension:

   • Start norepinephrine to maintain MAP ≥70 mmHg 1, 2
   • Add dobutamine to improve cardiac output 1, 2

3. Refractory cases:

   • Consider combination therapy with dobutamine and levosimendan 1, 2
   • If no improvement, consider mechanical circulatory support 1

Important Considerations and Pitfalls

• Avoid epinephrine when possible as it's associated with increased incidence of refractory shock and higher mortality risk 4, 3
• Limit duration of inotrope use as prolonged use is associated with increased mortality 5, 6
• Monitor for arrhythmias and myocardial ischemia, which are common complications of inotropic therapy 6
• Avoid excessive vasopressors which may increase myocardial oxygen demand 2
• Consider early mechanical circulatory support rather than escalating to multiple inotropes in refractory cases 1

Monitoring Response to Therapy

• Continuous ECG and invasive blood pressure monitoring 1
• Consider pulmonary artery catheterization to guide therapy 1
• Monitor for improvement in:
  • Cardiac index (target ≥2.2 L/min/m²)
  • Mean arterial pressure (target ≥70 mmHg)
  • Urine output (target >30 mL/h)
  • Lactate clearance
  • Mixed venous oxygen saturation (target ≥70%) 2

Despite their widespread use, there is a lack of robust evidence from randomized controlled trials to suggest clear benefit of one inotropic agent over another in cardiogenic shock. The choice is typically guided by blood pressure, concurrent arrhythmias, and drug availability 1.