A 58-year-old woman with severe calcific aortic stenosis (valve area 0.8 cm2, exertional syncope) is listed for open reduction of an ankle fracture. The surgeon requests spinal anaesthesia. Why is neuraxial blockade relatively contraindicated in this patient?

• A Spinal needles precipitate infective endocarditis in valvular lesions
• B Positioning for spinal insertion causes aortic valve embolism
• C Local anaesthetics cause spasm of the stenotic valve
• D Sympathetic blockade abolishes the fixed stroke volume compensation needed to maintain coronary perfusion ✓

Explanation

Severe aortic stenosis creates a fixed stroke volume: cardiac output depends on preload, afterload and heart rate, all of which sympathetic blockade disrupts abruptly. Vasodilation drops diastolic pressure while reflex tachycardia shortens diastolic coronary filling, precipitating collapse. This makes neuraxial anaesthesia a relative contraindication in severe AS and MS. General anaesthesia with careful haemodynamic titration is preferred. Infective endocarditis and valve spasm are not real mechanisms.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.