What is the recommended preoperative management for patients undergoing surgery for pheochromocytoma?

Preoperative Management for Pheochromocytoma Surgery

All patients with pheochromocytoma must receive alpha-adrenergic blockade for at least 10-14 days before surgery to prevent life-threatening hypertensive crises and arrhythmias during tumor manipulation. 1

Alpha-Adrenergic Blockade: The Foundation

Timing and Blood Pressure Targets

• Initiate alpha-blockade 10-14 days preoperatively with gradually escalating doses until blood pressure goals are achieved 1
• Target blood pressure: <130/80 mmHg supine AND systolic >90 mmHg standing 1, 2, 3
• These specific targets balance preventing intraoperative hypertensive crises while avoiding severe orthostatic hypotension 1

Choice of Alpha-Blocker

Either phenoxybenzamine or doxazosin is acceptable, though phenoxybenzamine may provide slightly better intraoperative hemodynamic stability. 1

Phenoxybenzamine (Non-selective, non-competitive α1- and α2-blocker):

• Standard dosing: 10 mg twice daily, adjusted every 2-4 days 1
• Provides less intraoperative hemodynamic instability according to the PRESCRIPT trial, the first randomized controlled trial comparing these agents 1
• More pronounced postoperative hypotension and side effects (orthostatic hypotension, edema, nasal congestion) 4

Doxazosin (Selective, competitive α1-blocker):

• Alternative with potentially fewer side effects 1
• Equivalent efficacy for blood pressure control but may require more additional antihypertensive agents 4
• Other selective α1-blockers include prazosin and terazosin 1

Additional Antihypertensive Agents

If target blood pressure is not achieved with alpha-blockade alone:

• Add calcium channel blockers (nifedipine slow-release) for refractory hypertension 1
• Calcium channel blockers can also be used as monotherapy in patients with normal to mildly elevated blood pressure or severe orthostatic hypotension 1
• Consider metyrosine (tyrosine hydroxylase inhibitor) as add-on therapy where available 1, 5
• Metyrosine is FDA-approved for preoperative preparation and may facilitate better blood pressure control, reduce blood loss, and decrease intraoperative fluid requirements 5, 6

Beta-Adrenergic Blockade: Critical Timing

NEVER initiate beta-blockers before adequate alpha-blockade is established—this can precipitate a hypertensive crisis from unopposed alpha-adrenergic stimulation. 1, 3

• Add beta-blockers ONLY after alpha-blockade if tachyarrhythmias develop 1, 2
• Preferably use β1-selective agents 1
• Monotherapy with beta-blockers is absolutely contraindicated 1

Volume Expansion: Preventing Postoperative Hypotension

Implement aggressive volume expansion 24 hours before surgery:

• High-sodium diet during the preoperative period 1, 2
• Administer 1-2 liters of intravenous saline 24 hours prior to surgery 1
• Use compressive stockings to reduce orthostatic hypotension risk 1, 2
• This regimen counteracts the vasodilation and expanded volume capacity that occurs after tumor removal 5

Intraoperative Management Preparation

Ensure availability of specific vasoactive agents for immediate use:

For Hypertensive Crises:

• Magnesium sulfate 1, 2
• Intravenous phentolamine (α-adrenergic antagonist) 1, 2
• Calcium channel blockers 1, 2
• Nitroprusside or nitroglycerin 1, 2

For Tachycardia:

• Intravenous esmolol (β1-selective blocker) 1, 2

For Postoperative Hypotension:

• Large volumes of plasma may be required after tumor removal 5
• Aggressive fluid resuscitation is essential 2, 7

Postoperative Monitoring

Critical metabolic monitoring is required:

• Monitor glucose levels closely—hypoglycemia commonly occurs after the sudden reduction in catecholamine levels 1, 2, 3, 7
• Maintain continuous blood pressure and electrocardiogram monitoring 5

Biochemical Confirmation of Complete Resection

• Measure plasma or urine metanephrines at 2-8 weeks postoperatively to confirm complete tumor removal 1, 2, 3, 7
• Perform imaging at 3-6 months postoperatively 1, 2

Common Pitfalls to Avoid

Critical errors that can be fatal:

• Starting beta-blockers before alpha-blockade (causes hypertensive crisis) 1, 3
• Inadequate duration of preoperative preparation (<10 days) 1
• Insufficient volume expansion leading to severe postoperative hypotension 5
• Never perform fine needle biopsy of suspected pheochromocytoma—this can precipitate a fatal hypertensive crisis 7
• Failing to monitor for hypoglycemia postoperatively 1, 7

Special Considerations

For dopamine-only secreting tumors (rare):

• Alpha-adrenergic blockade is not advised as these patients are typically normotensive or hypotensive 1

When metyrosine is used:

• Maintain adequate intravascular volume intraoperatively and postoperatively to avoid hypotension from vasodilatation 5
• Be aware that metyrosine adds to sedative effects of alcohol and CNS depressants 5
• Despite metyrosine use, phentolamine may still be needed intraoperatively for hypertensive crises 5