What is the recommended anesthesia approach for patients with severe aortic stenosis undergoing surgery?

Anesthesia for Severe Aortic Stenosis

For patients with severe aortic stenosis undergoing noncardiac surgery, maintain hemodynamic stability by avoiding hypotension, preserving sinus rhythm, preventing tachycardia, and ensuring adequate preload while using careful titration of anesthetic agents with invasive monitoring. 1

Preoperative Assessment and Risk Stratification

Essential Preoperative Evaluation

• Obtain echocardiography within the past year or if clinical status has changed to assess severity (valve area <1.0 cm², peak velocity ≥4 m/sec, or mean gradient ≥40 mmHg defines severe AS) 1
• Assess for symptoms (dyspnea, angina, syncope) as these significantly increase perioperative mortality risk (OR: 2.7 for symptomatic severe AS) 1
• Evaluate left ventricular ejection fraction, as LVEF <50% indicates higher risk and warrants consideration of valve intervention before elective surgery 1, 2
• Consider stress testing in asymptomatic patients to unmask exercise-induced symptoms 1

Preoperative Management Decisions

For symptomatic patients with severe AS, aortic valve replacement should be performed before elective noncardiac surgery. 1 If the patient is high-risk for valve replacement, consider TAVR or balloon aortic valvuloplasty as a bridge to surgery 1. However, selected patients who refuse or are not candidates for valve replacement can proceed with noncardiac surgery under careful monitoring 3, 4.

Intraoperative Anesthetic Management

Hemodynamic Goals (Critical Priorities)

The three cardinal principles are: (1) avoid hypotension to maintain coronary perfusion pressure, (2) maintain sinus rhythm and avoid tachycardia to preserve diastolic filling time, and (3) avoid myocardial depression from anesthetic agents. 1

Monitoring Requirements

• Use intraarterial blood pressure monitoring for continuous hemodynamic assessment 3, 4
• Ensure the anesthesia team is aware of AS severity and integrates this into the anesthetic plan 4

Anesthetic Agent Selection

Remimazolam for induction and maintenance requires significantly less vasopressor support compared to propofol or midazolam-based regimens in severe AS patients. 5 In a comparative study, remimazolam required lower doses of ephedrine (2 mg vs. 8 mg with propofol/sevoflurane, P<0.001) and phenylephrine (0 mg vs. 0.15 mg, P=0.03) during induction, and less noradrenaline during maintenance (0.019 vs. 0.042 μg/kg/min, P=0.02) 5.

For opioid selection, remifentanil can be used with careful titration. During maintenance with nitrous oxide, an infusion rate of 0.4 mcg/kg/min is appropriate, with supplemental boluses of 1 mcg/kg every 2-5 minutes as needed 6. When combined with isoflurane or propofol, lower infusion rates (0.25 mcg/kg/min) are recommended 6.

Neuraxial Anesthesia Considerations

Combined spinal-epidural anesthesia with careful titration can be safer than general anesthesia for certain procedures (e.g., lumbar spine surgery in prone position), as general anesthesia with positive-pressure ventilation may further compromise cardiac output. 7 However, this requires meticulous dose titration to avoid sudden sympathectomy and hypotension 7. Traditional teaching has contraindicated neuraxial techniques, but modern evidence supports their use with appropriate monitoring 7.

Management of Hypotension

• Treat hypotensive events promptly, primarily with phenylephrine to maintain systemic vascular resistance and coronary perfusion 4
• Avoid agents that cause significant vasodilation or myocardial depression 1

Postoperative Management

Immediate Postoperative Period

• Continue invasive hemodynamic monitoring in the immediate postoperative period 1
• Consider ICU admission for high-risk patients 1
• Maintain stable hemodynamics and avoid rapid volume shifts 1
• Monitor vigilantly for arrhythmias, which may severely compromise cardiac output in these patients 1

Transition to Postoperative Analgesia

If remifentanil was used intraoperatively, administer alternative analgesics (e.g., morphine 0.15 mg/kg IV) 20 minutes before anticipated end of surgery, as remifentanil provides no residual analgesia within 5-10 minutes of discontinuation 6. This approach does not delay recovery of respiratory drive 6.

Special Populations and Considerations

Reduced Ejection Fraction

For patients with severe AS and LVEF <50%, intervention is appropriate regardless of surgical risk (Class I recommendation), and medical management alone is rarely appropriate 2. For low-flow, low-gradient AS, perform dobutamine stress echocardiography to distinguish true-severe from pseudo-severe AS before proceeding 2.

Very Severe AS

Patients with Vmax ≥5 m/sec or mean gradient ≥60 mmHg are at particularly high risk and warrant heightened vigilance 1.

Common Pitfalls to Avoid

• Do not induce rapid vasodilation with neuraxial blockade or anesthetic agents without immediate vasopressor availability 7
• Do not allow tachycardia as this reduces diastolic filling time and coronary perfusion in the hypertrophied, non-compliant left ventricle 1
• Do not use remifentanil boluses for postoperative pain management as this is not recommended; transition to longer-acting analgesics before discontinuation 6
• Do not proceed with elective surgery in symptomatic severe AS patients without first considering valve intervention 1