What is the treatment for Low Cardiac Output Syndrome (LCOS), particularly in post-cardiac surgery patients or those with severe heart failure?

Treatment of Low Cardiac Output Syndrome (LCOS)

Positive inotropes and/or vasopressors are the recommended first-line medical treatment for LCOS during cardiac surgery, with specific consideration for levosimendan in patients with reduced left ventricular function. 1

Initial Management Algorithm

First-Line Pharmacological Treatment

• Initiate positive inotropes and/or vasopressors immediately as first-line therapy for LCOS during cardiac surgery (Class I recommendation, Level A evidence). 1

• The most commonly used agents include dobutamine, epinephrine, norepinephrine, phosphodiesterase III inhibitors (milrinone), and calcium sensitizers (levosimendan). 1

• Before starting inotropes, correct reversible causes: rule out cardiac tamponade, graft dysfunction, hypovolemia, coronary artery or bypass graft spasm, and electrolyte abnormalities. 2

Specific Agent Selection

For standard LCOS:

• Dobutamine is indicated for short-term inotropic support in cardiac decompensation due to depressed contractility from organic heart disease or cardiac surgical procedures. 3
• Milrinone (phosphodiesterase III inhibitor) produces dose-related increases in myocardial contractility and arterial vasodilation, with therapeutic plasma concentrations of 100-300 ng/mL. 4

For patients with poor left ventricular function:

• Levosimendan should be considered (Class IIa, Level A) to reduce the risk of LCOS in patients with reduced left ventricular ejection fraction undergoing isolated CABG. 1
• Levosimendan may be considered (Class IIb, Level B) to improve survival in patients with poor LV function and established perioperative LCOS. 1
• In rescue therapy scenarios, levosimendan at 0.1 µg/kg/min for 24 hours significantly increases ejection fraction from 27% to 38% within 24 hours and to 45% within 48 hours. 5

Critical Monitoring Requirements

• Transesophageal echocardiography (TOE) should be considered (Class IIa, Level B) in all open-heart and thoracic aortic procedures to assess cardiac function, detect mechanical complications, and guide therapy. 1

• Invasive hemodynamic monitoring with pulmonary artery catheter may be indicated in selected cases (Class IIb, Level B) when fluid status, perfusion, or vascular resistance is uncertain. 1

• Monitor cardiac output, systemic vascular resistance, filling pressures, and end-organ perfusion (urine output, lactate, mixed venous oxygen saturation). 6, 7

Advanced Interventions for Refractory LCOS

When conventional therapy fails:

• Intra-aortic balloon counterpulsation (IABC) is indicated for patients not responding rapidly to fluid administration, vasodilation, and inotropic support. 1

• IABC increases aortic diastolic pressure and coronary flow while decreasing afterload, dramatically improving hemodynamics. 1

• Mechanical circulatory support should be considered when other strategies are ineffective, choosing among IABC, percutaneous cardiopulmonary support, or ventricular assist devices based on required strength and duration of support. 2

• Extracorporeal life support (ECLS) should be available at all times (Class I recommendation) for emergency institution. 1

Special Considerations and Pitfalls

Right ventricular failure:

• Open-chest management is useful when inotropic support is unsuccessful for right heart failure. 2
• Consider specific right ventricular support strategies including inhaled pulmonary vasodilators and mechanical support. 7

Pacing strategies:

• Atrial or AV sequential pacing is very useful to obtain reasonable cardiac output and prevent arrhythmias. 2

Critical monitoring parameters:

• Careful monitoring of blood gas and electrolytes is essential to maintain hemodynamics and prevent arrhythmias. 2
• The cardiopulmonary bypass circuit should be kept functional until the patient's chest has been closed (Class I recommendation). 1

Timing considerations:

• LCOS typically develops within 6-18 hours after cardiac surgery, with approximately 25% of children experiencing cardiac index <2 L/min/m². 7
• Response to levosimendan in terms of decreased need for inotropes and vasopressors predicts survival. 5

Important Contraindications

• Long-term use of inotropes is not recommended: neither dobutamine nor any cyclic-AMP-dependent inotrope has been shown safe or effective in long-term treatment of congestive heart failure, with increased risk of hospitalization and death. 3

• Experience with intravenous dobutamine in controlled trials does not extend beyond 48 hours of repeated boluses and/or continuous infusions. 3

• Routine use of parenteral inotropes in normotensive patients without evidence of decreased organ perfusion is not recommended (Class III, Level B). 1