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Phaeochromocytoma Intraoperative Crisis — FRCA Final MCQ

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HardGeneral AnaesthesiaPhaeochromocytoma Intraoperative CrisisFRCA Final

A 50-year-old man is undergoing excision of a phaeochromocytoma after preoperative phenoxybenzamine followed by propranolol. During tumour manipulation, his arterial pressure rises abruptly to 250/140 mmHg and his heart rate to 140 beats/min. The surgeon stops manipulating the tumour and adequate anaesthetic depth is confirmed. An antihypertensive infusion has not yet been connected. Which drug is most appropriate as an immediate IV bolus to provide additional competitive alpha-adrenoceptor blockade before treating any residual tachycardia?

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Correct answer: C — Phentolamine

Phentolamine is the best immediate bolus treatment. It is a short-acting, competitive, non-selective alpha1/alpha2 antagonist that directly opposes catecholamine-mediated vasoconstriction. The UK SmPC recommends 2–5 mg IV, repeated as required with continuous blood-pressure monitoring, for crises during phaeochromocytoma removal. Sodium nitroprusside and nicardipine are effective titratable vasodilator alternatives but are generally administered by infusion and do not directly antagonise alpha-adrenoceptors. Esmolol treats tachycardia rather than the principal alpha-mediated vasoconstriction; further beta-blockade should follow control of arterial pressure if still required. Labetalol has proportionally greater beta- than alpha-blocking activity and is therefore less suitable for rapidly reversing a catecholamine-driven vasoconstrictive crisis.

Reference: Electronic Medicines Compendium. Phentolamine mesilate 10 mg/ml Solution for Injection, SmPC sections 4.1, 4.2 and 5.1. Updated 20 October 2025. https://www.medicines.org.uk/emc/product/101496/smpc