What are the anesthetic implications for pheochromocytoma removal?

Anesthetic Implications for Pheochromocytoma Removal

The most critical anesthetic implication for pheochromocytoma removal is mandatory preoperative alpha-adrenergic blockade for 10-14 days before surgery to prevent potentially life-threatening hypertensive crises and arrhythmias during tumor manipulation. 1, 2

Preoperative Management

Alpha-Adrenergic Blockade

• Preoperative alpha-adrenergic blockade must be initiated at least 7-14 days before surgery with gradually increasing dosages 1, 2
• Blood pressure targets: <130/80 mmHg supine and systolic blood pressure >90 mmHg in upright position 1, 2
• Two main options for alpha blockade:
  • Non-selective, non-competitive alpha-blocker: Phenoxybenzamine (starting dose 10 mg twice daily with adjustments every 2-4 days) 1, 3
  • Selective alpha-1 blockers: Doxazosin, prazosin, or terazosin 1
• The PRESCRIPT trial showed phenoxybenzamine may provide less intraoperative hemodynamic instability compared to doxazosin, though both are effective 1, 4

Beta-Adrenergic Blockade

• Beta-blockers should ONLY be added AFTER adequate alpha blockade to control tachyarrhythmias 1, 2
• Never use beta-blockers alone as monotherapy, as this can precipitate hypertensive crisis due to unopposed alpha-adrenergic stimulation 5
• Preferably use cardioselective beta-1 blockers when needed 1

Additional Preoperative Measures

• High-sodium diet and administration of 1-2 liters of saline 24 hours prior to surgery 1, 2
• Use of compressive stockings to reduce risk of orthostatic and postoperative hypotension 1, 2
• Calcium channel blockers may be used as adjuncts to alpha-blockers for refractory hypertension 1, 2
• Metyrosine (alpha-methyl-p-tyrosine), a catecholamine synthesis inhibitor, can be used as an add-on medication where available to further reduce catecholamine production 1, 6

Intraoperative Management

Hemodynamic Management

• Hypertension during surgery may be treated with:
  • Magnesium sulfate
  • Intravenous alpha-adrenergic antagonist (phentolamine)
  • Calcium channel blockers
  • Nitroprusside
  • Nitroglycerin 1, 2
• Tachycardia can be treated with intravenous beta-blockers such as esmolol 2, 5
• Patients who receive adequate preoperative alpha blockade (particularly higher doses of phenoxybenzamine) require significantly less intraoperative vasodilators 7

Critical Phases

• Most significant hemodynamic instability occurs during:
  • Induction of anesthesia
  • Tumor manipulation
  • Immediately after tumor removal (risk of hypotension) 2
• Careful monitoring of blood pressure and heart rate is essential throughout the procedure 2

Surgical Approach Considerations

• Laparoscopic adrenalectomy is preferred for most pheochromocytomas, showing better intraoperative hemodynamic stability compared to open surgery 2
• Open surgery should be considered for tumors with high suspicion of malignancy, large size (>6 cm), or local invasion 2

Postoperative Management

Immediate Postoperative Care

• Aggressive treatment of postoperative hypotension is essential due to sudden decrease in catecholamine levels 8
• Close monitoring of blood glucose levels is crucial as hypoglycemia commonly occurs after reduction of catecholamine levels 8
• For bilateral adrenalectomy, high-dose hydrocortisone (150 mg/day) should be administered during the immediate postoperative period 8

Monitoring

• Postoperative biochemical testing should be performed 2-8 weeks after surgery to confirm complete resection 1, 8
• Imaging should be done at 3-6 months postoperatively 1, 8

Special Considerations and Pitfalls

Potential Complications

• Inadequate preoperative alpha blockade can lead to severe hypertensive crises during tumor manipulation 1, 6
• Excessive alpha blockade can cause significant postoperative hypotension requiring vasopressors 4
• Premature beta blockade (before adequate alpha blockade) can precipitate hypertensive crisis 5
• Patients with exclusively dopamine-producing pheochromocytomas (indicated by isolated elevation of plasma methoxytyramine) do not require preoperative alpha blockade 1

Comprehensive Evaluation

• All patients with adrenal masses should undergo comprehensive hormonal evaluation, including testing for both catecholamine excess and other hormone abnormalities 9
• Never perform adrenal biopsy without excluding pheochromocytoma first, as this can trigger life-threatening hypertensive crisis 9

By following these guidelines for preoperative preparation and intraoperative management, the anesthetic risks associated with pheochromocytoma removal can be significantly minimized, improving patient outcomes and reducing perioperative morbidity and mortality.