What is the intraoperative management of a patient in cardiogenic shock undergoing emergent Coronary Artery Bypass Grafting (CABG), specifically regarding infusion management?

Intraoperative Management of Cardiogenic Shock During Emergent CABG: Infusion Strategy

For patients in cardiogenic shock requiring emergent CABG, a combination of vasopressors and inotropes is recommended, with norepinephrine as the first-line vasopressor and dobutamine as the first-line inotrope, supplemented by intra-aortic balloon counterpulsation for hemodynamic stabilization. 1

Initial Hemodynamic Assessment and Monitoring

• Immediate invasive hemodynamic monitoring is essential:
  • Arterial line placement for continuous blood pressure monitoring 1
  • Pulmonary artery catheter consideration for advanced hemodynamic assessment 1
  • Intraoperative transesophageal echocardiography (TEE) for evaluation of ventricular function, valvular function, and to rule out mechanical complications 1

Pharmacological Support Strategy

First-Line Agents:

1. Vasopressors:

   • Norepinephrine (0.01-0.3 μg/kg/min): First-line vasopressor for maintaining systemic vascular resistance and mean arterial pressure ≥65 mmHg 1
   • Titrate to maintain coronary perfusion pressure while avoiding excessive afterload

2. Inotropes:

   • Dobutamine (2.5-10 μg/kg/min): First-line inotrope for improving cardiac contractility and output 1
   • Particularly useful when cardiac index remains <2.2 L/min/m² despite adequate filling pressures

Second-Line/Adjunctive Agents:

• Epinephrine (0.01-0.1 μg/kg/min): Consider when combined inotropic and vasopressor effects are needed for refractory shock
• Vasopressin (0.01-0.04 U/min): Can be added to norepinephrine for catecholamine-resistant shock
• Milrinone (0.25-0.75 μg/kg/min): Consider in right ventricular dysfunction or when beta-receptor downregulation is suspected (loading dose often omitted in shock)

Mechanical Circulatory Support

• Intra-aortic balloon pump (IABP) is recommended for patients in cardiogenic shock when pharmacological therapy fails to stabilize hemodynamics 1

  • Should be placed pre-operatively or early intraoperatively
  • Serves as a stabilizing measure before and during revascularization 1

• Short-term mechanical support (e.g., ECMO, Impella) may be considered in refractory shock not responding to IABP and pharmacological therapy 1

Fluid Management

• Rapid volume loading is recommended for patients without clinical evidence of volume overload 1
• Judicious fluid administration guided by:
  • Pulmonary artery catheter measurements
  • Dynamic parameters (stroke volume variation)
  • TEE assessment of ventricular filling

Optimizing Determinants of Coronary Perfusion

• Target heart rate: 60-80 beats/minute to optimize diastolic filling time
• Maintain diastolic blood pressure >60-65 mmHg to ensure adequate coronary perfusion 1
• Optimize right ventricular and left ventricular end-diastolic pressures 1

Additional Perioperative Considerations

• Oxygenation: Ensure arterial oxygen saturation >90% 1
• Rhythm management: Promptly correct arrhythmias or conduction abnormalities contributing to hemodynamic instability 1
• Glucose control: Maintain blood glucose ≤180 mg/dL while avoiding hypoglycemia 2
• Acid-base balance: Monitor and correct metabolic acidosis which can reduce catecholamine responsiveness

Post-Bypass Management

• Continue vasopressor/inotropic support as needed during separation from cardiopulmonary bypass
• Consider ultrafiltration for patients with refractory congestion 1
• Maintain IABP support post-operatively until hemodynamic stability is achieved

Common Pitfalls to Avoid

1. Excessive vasopressor use: Can increase myocardial oxygen demand and afterload, potentially worsening cardiac function
2. Inadequate preload: Ensure optimal filling pressures before escalating inotropes/vasopressors
3. Delayed mechanical support: Consider early IABP placement rather than escalating multiple pharmacological agents
4. Beta-blockers or calcium channel blockers: Should not be administered to patients in cardiogenic shock 1
5. Overlooking right ventricular dysfunction: May require specific management with pulmonary vasodilators and tailored inotropic support

The SHOCK trial demonstrated that emergency CABG is an effective strategy for patients in cardiogenic shock with suitable coronary anatomy, with outcomes comparable to PCI despite higher-risk profiles 3. Early and aggressive hemodynamic support with the appropriate combination of vasopressors, inotropes, and mechanical circulatory assistance is essential to optimize outcomes in this critically ill population.