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Vasopressor Choice Severe AS — FRCA Final MCQ

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ModerateGeneral AnaesthesiaVasopressor Choice Severe ASFRCA Final

A 70-year-old man (ASA IV) with aortic stenosis (AVA 0.5 cm², mean gradient 60 mmHg) is undergoing emergency laparotomy. During induction with etomidate, his systolic BP drops from 110 to 65 mmHg. Which vasopressor is most appropriate to restore blood pressure?

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Correct answer: E — Metaraminol 0.5 mg IV bolus (pure alpha agonist)

In severe aortic stenosis, maintaining systemic vascular resistance (SVR) is critical to maintain coronary perfusion pressure. Phenylephrine (predominantly alpha-1 agonist) or metaraminol (alpha-1 with some beta activity) are preferred because they increase SVR without significant tachycardia. Tachycardia is dangerous in AS (reduces diastolic filling time and coronary perfusion). Ephedrine's beta effects may cause unwanted tachycardia. Low-dose noradrenaline infusion is an excellent option for sustained support. Vasopressin is also acceptable. Avoid adrenaline boluses (excessive tachycardia and arrhythmia risk).

Reference: RCOA – 2023 – Cardiac anaesthesia; ESC – 2021 – Valvular heart disease