What is the preoperative preparation for a patient undergoing pheochromocytoma surgery?

Preoperative Preparation for Pheochromocytoma Surgery

Preoperative preparation for pheochromocytoma surgery requires alpha-adrenergic blockade started 7-14 days before surgery, with phenoxybenzamine showing less intraoperative hemodynamic instability compared to selective alpha-blockers. 1

Alpha-Adrenergic Blockade Protocol

First Step: Alpha Blockade

• Alpha-adrenergic blockers are the primary treatment to control catecholamine excess and prevent surgical complications 1, 2
• Options include:
  • Non-selective alpha-blocker: Phenoxybenzamine (40-80 mg/day)
  • Selective alpha-1 blockers: Doxazosin, prazosin, or terazosin
• Start at least 7-14 days preoperatively with gradually increasing dosages until blood pressure targets are achieved 1
• Target blood pressure: <130/80 mmHg supine and >90 mmHg systolic when standing 2

Second Step: Beta Blockade (if needed)

• Add beta-blockers only after adequate alpha-blockade if tachycardia persists 2
• Preferably use beta-1 selective blockers to control tachycardia 1
• Never start beta-blockers before alpha-blockers as this can worsen hypertension due to unopposed alpha-stimulation

Alternative or Adjunctive Medications

• Calcium channel blockers: Can be used as adjuncts to alpha-blockers for refractory hypertension or as monotherapy in cases with normal to mildly elevated blood pressure 1
• Metyrosine: FDA-approved for preoperative preparation, reduces catecholamine synthesis 3

Volume Expansion Protocol

• Implement high-sodium diet and administer 1-2 liters of saline 24 hours prior to surgery 1
• Use compressive stockings to reduce orthostatic hypotension 1
• Adequate intravascular volume must be maintained intraoperatively and postoperatively to avoid hypotension 3

Intraoperative Management Considerations

• Continuous monitoring of blood pressure and electrocardiogram during surgery 3
• Be prepared for:
  • Hypertensive crises during tumor manipulation (may require phentolamine) 3
  • Life-threatening arrhythmias (may require beta-blockers or lidocaine) 3
  • Hypotension after tumor removal (requires volume replacement) 3

Common Pitfalls and Caveats

1. Inadequate preoperative alpha blockade: Can lead to dangerous intraoperative hypertensive crises
2. Starting beta-blockers before alpha-blockers: Can precipitate hypertensive crisis due to unopposed alpha-adrenergic stimulation
3. Insufficient volume expansion: Can lead to severe hypotension after tumor removal
4. Inadequate monitoring: Continuous BP and ECG monitoring is essential during surgery
5. Insufficient preparation time: Alpha blockade should be started at least 7-14 days before surgery

Evidence Considerations

The PRESCRIPT trial, the first randomized controlled trial on presurgical treatment in patients with pheochromocytomas, found that while both phenoxybenzamine and doxazosin effectively controlled blood pressure, phenoxybenzamine resulted in less intraoperative hemodynamic instability 1. However, phenoxybenzamine is associated with more pronounced postoperative hypotension and side effects like orthostatic hypotension and nasal congestion 4.

Regardless of the specific alpha-blocker chosen, adequate preoperative preparation is essential for reducing perioperative complications and mortality in pheochromocytoma surgery.