What are the anaesthetic considerations for patients with aortic stenosis undergoing surgery?

Anaesthetic Considerations for Patients with Aortic Stenosis

Patients with severe aortic stenosis require careful perioperative management with invasive hemodynamic monitoring and optimization of loading conditions to minimize the risk of cardiovascular complications during non-cardiac surgery. 1

Preoperative Assessment

• Echocardiography is essential for all patients with known or suspected aortic stenosis prior to surgery to assess severity, especially if no echocardiogram has been performed within the past year or if clinical status has changed 1
• Severe aortic stenosis is defined as:
  • Valve area <1.0 cm² or indexed valve area ≤0.6 cm²/m² 1
  • Maximum jet velocity ≥4 m/sec 1
  • Mean aortic pressure gradient ≥40 mm Hg 1
• Assess for symptoms (dyspnea, angina, syncope) which significantly increase perioperative risk 1
• Evaluate left ventricular function, as reduced ejection fraction (<50%) indicates higher risk and may warrant valve intervention before elective surgery 1
• Consider stress testing in asymptomatic patients to unmask exercise-induced symptoms 1

Risk Stratification

• Severe aortic stenosis is a well-established risk factor for perioperative mortality and myocardial infarction 1
• Risk predictors for 30-day mortality and postoperative MI include:
  • High-risk surgery (OR: 7.3) 1
  • Symptomatic severe AS (OR: 2.7) 1
  • Coexisting moderate/severe mitral regurgitation (OR: 9.8) 1
  • Pre-existing coronary artery disease (OR: 2.7) 1

Preoperative Management Decisions

• For symptomatic patients with severe AS:
  • Aortic valve replacement should be considered before elective non-cardiac surgery 1
  • If high-risk for valve replacement, consider TAVI or balloon aortic valvuloplasty as a bridge to surgery 1
• For asymptomatic patients with severe AS:
  • Low to intermediate-risk non-cardiac surgery can be performed safely 1
  • For high-risk surgery, consider aortic valve replacement if patient is not at high risk for valve surgery 1

Intraoperative Management

Hemodynamic Goals

• Maintain sinus rhythm and avoid tachycardia which can decrease diastolic filling time and coronary perfusion 1, 2
• Avoid hypotension which can reduce coronary perfusion pressure 1
• Maintain adequate preload to ensure left ventricular filling 3
• Avoid myocardial depression from anesthetic agents 1
• Maintain systemic vascular resistance to preserve forward flow 3

Monitoring

• Invasive arterial blood pressure monitoring is essential 1, 3
• Consider central venous pressure monitoring 1
• Transesophageal echocardiography may be valuable for high-risk cases 1
• Pulmonary artery catheterization may be considered in complex cases 1

Anesthetic Technique

• General anesthesia with careful titration of agents to maintain hemodynamic stability is traditionally preferred 3
• Neuraxial anesthesia has been historically contraindicated due to concerns about sympathetic blockade and hemodynamic instability, though recent evidence suggests it may be considered in carefully selected patients with appropriate monitoring and vasopressor support 4
• If regional anesthesia is used, ensure gradual onset of sympathetic blockade and aggressive treatment of hypotension 4

Pharmacological Considerations

• Phenylephrine is often the vasopressor of choice to maintain systemic vascular resistance 3
• Avoid drugs that cause significant vasodilation or myocardial depression 1
• Treat bradycardia promptly but avoid excessive tachycardia 2
• Maintain euvolemia with careful fluid management 1

Postoperative Management

• Continue invasive hemodynamic monitoring in the immediate postoperative period 1
• Consider intensive care unit setting for high-risk patients 1
• Maintain stable hemodynamics and avoid rapid changes in volume status 1
• Monitor for signs of heart failure, which may be exacerbated postoperatively 5
• Continue vigilance for arrhythmias which may compromise cardiac output 1

Special Considerations

• Emergency surgery in patients with severe AS carries higher risk but can be performed with appropriate monitoring and management 3
• Patients with low-flow, low-gradient AS with reduced ejection fraction require special attention to distinguish true-severe from pseudo-severe AS 1
• Very severe AS (Vmax ≥5 m/sec or mean gradient ≥60 mmHg) indicates particularly high risk 1
• Patients with AS undergoing cardiac surgery for other indications should have valve replacement considered 1