A 39-year-old woman with biochemically confirmed phaechromocytoma is prepared for adrenalectomy. Her surgeon plans to start a beta blocker for palpitations before any other agent. Why is this sequence dangerous?

• A Beta blockers mask the biochemical diagnosis and delay surgery
• B Beta blockers precipitate rebound hypoglycaemia that mimics catecholamine excess
• C Beta blockers increase catecholamine synthesis within the tumour
• D Blocking beta-mediated vasodilation leaves alpha-mediated vasoconstriction unopposed, causing hypertensive crisis ✓

Explanation

Alpha-adrenergic vasoconstriction must be blocked first, classically with phenoxybenzamine, before any beta blocker is introduced. Giving a beta blocker first removes beta-2 vasodilatory tone while alpha tone persists, raising blood pressure catastrophically. Beta blockade is added afterwards solely to control reflex tachycardia and arrhythmias.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.