## Preoperative Management of Pheochromocytoma **Key Point:** Phenoxybenzamine is the gold-standard first-line agent for preoperative α-blockade in pheochromocytoma. It is a non-selective, irreversible α-adrenergic antagonist that provides sustained blood pressure control and prevents intraoperative hypertensive crises. ### Mechanism and Rationale Pheochromocytoma causes uncontrolled catecholamine release, leading to: - Severe hypertension - Arrhythmias - Myocardial ischemia - Intraoperative catecholamine surge ("catecholamine storm") Phenoxybenzamine achieves **irreversible α-blockade**, which: 1. Prevents catecholamine-induced vasoconstriction 2. Allows peripheral vasodilation and blood pressure stabilization 3. Reduces the risk of intraoperative hypertensive crisis 4. Restores intravascular volume (patients are typically volume-depleted due to catecholamine-induced vasoconstriction) ### Preoperative Protocol | Step | Drug | Timing | Rationale | |------|------|--------|----------| | 1 | Phenoxybenzamine | 7–10 days before surgery | α-blockade; allows volume expansion | | 2 | β-blocker (propranolol) | After α-blockade established | Prevent reflex tachycardia; never give β-blocker first | | 3 | Calcium channel blocker (optional) | If additional control needed | Adjunctive vasodilation | **High-Yield:** Never initiate β-blockade before α-blockade. Unopposed β-blockade (loss of β~2~-mediated vasodilation) worsens hypertension and can precipitate a hypertensive crisis. **Clinical Pearl:** Phenoxybenzamine is dosed 10 mg orally twice daily, titrated up to 40–80 mg/day. The goal is to achieve orthostatic hypotension (systolic BP drop of 10–15 mmHg on standing), which indicates adequate α-blockade and volume repletion. **Warning:** Phenoxybenzamine has a long half-life (~24 hours) and irreversible binding. Hypotension post-surgery is common and usually self-limited; avoid abrupt discontinuation.
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