Anesthetic Management of Pheochromocytoma 

๐Ÿงฌ Introduction

Pheochromocytoma is a rare catecholamine-secreting tumor arising from chromaffin cells of the adrenal medulla or extra-adrenal paraganglia. It causes paroxysmal or sustained hypertension due to excess secretion of epinephrine, norepinephrine, and dopamine.


๐Ÿ“Œ Key Points

  • Rule of 10s (classic but outdated):
    • 10% bilateral
    • 10% extra-adrenal
    • 10% malignant
    • 10% familial
  • Now, ~30โ€“40% are hereditary (e.g., MEN 2, VHL, NF1, SDH mutations)


๐Ÿ”ฌ Pathophysiology

Catecholamines secreted:

  • Norepinephrine: ฮฑ1 > ฮฒ1 โ†’ Vasoconstriction, HTN
  • Epinephrine: ฮฒ1, ฮฒ2, ฮฑ1 โ†’ Tachycardia, vasodilation or constriction depending on receptor distribution
  • Dopamine: Renal vasodilation (low dose), vasoconstriction (high dose)

Symptoms (due to catecholamine surges):

  • Classic triad: Headache + Palpitations + Sweating
  • Labile/paroxysmal HTN
  • Orthostatic hypotension
  • Hyperglycemia
  • Weight loss, anxiety, tremors


๐Ÿ”Ž Diagnosis

  • Biochemical confirmation:
    • Plasma free metanephrines (most sensitive)
    • 24h urine metanephrines, catecholamines
  • Imaging:
    • CT/MRI of adrenals
    • MIBG scintigraphy (for extra-adrenal or metastatic)


๐Ÿฉบ Preoperative Preparation (Cornerstone of Anesthesia Success)

Goal: Achieve hemodynamic stability and volume repletion pre-surgery.

1. Alpha Blockade (Mandatory)

  • Phenoxybenzamine (non-selective, irreversible)
    • Start 10โ€“14 days before surgery
    • Titrate until BP <130/80 mmHg seated and >90 mmHg standing
    • Side effects: Orthostatic hypotension, nasal stuffiness
  • Prazosin/doxazosin (selective ฮฑ1): Fewer side effects

2. Beta Blockade (Only after alpha blockade!)

  • Prevents unopposed ฮฑ vasoconstriction
  • For tachycardia or arrhythmias
  • Propranolol, atenolol, labetalol (ฮฑ and ฮฒ)

3. Volume Expansion

  • Catecholamines cause chronic vasoconstriction and hypovolemia.
  • Salt intake + IV fluids pre-op to restore intravascular volume.

4. Other Drugs

  • Calcium channel blockers: Nicardipine for BP control
  • Metyrosine: Inhibits catecholamine synthesis; used in refractory cases


๐Ÿง  Anesthetic Goals

Objective

Rationale

Control hypertension

Catecholamine surge during induction/surgery

Avoid tachycardia

To prevent myocardial ischemia

Prevent intra-op hypertensive crises

Stress response, tumor handling

Prepare for post-op hypotension

Due to sudden drop in catecholamines

Ensure adequate volume status

To avoid severe hypotension post-tumor removal


๐Ÿ’‰ Intraoperative Management

โœ… Monitoring

  • Invasive BP (A-line) โ€“ Beat-to-beat BP
  • CVP/Arterial line
  • Large-bore IVs, central line if needed
  • Urine output
  • Blood glucose hourly (catecholamines cause hyperglycemia)
  • Cardiac monitoring (arrhythmias)

โœ… Induction

  • Avoid sympathetic stimulation:
    • Fentanyl, midazolam, propofol or etomidate
    • Avoid ketamine (sympathomimetic)
    • Rocuronium or cisatracurium (avoid histamine-releasing relaxants like atracurium)
  • Deep anesthesia to blunt intubation response (lidocaine, opioids)

โœ… Maintenance

  • Volatile agents: Sevoflurane or desflurane (titrate carefully)
  • Short-acting opioids: Remifentanil preferred
  • Magnesium sulfate: Anti-hypertensive, anti-arrhythmic, inhibits catecholamine release

โœ… Intraoperative Hypertension (esp. tumor manipulation)

  • Nitroprusside: Potent vasodilator
  • Phentolamine: Short-acting ฮฑ-blocker
  • Esmolol: For tachycardia
  • Nicardipine, clevidipine: Preferred CCBs

โœ… Hypotension After Tumor Removal

  • Due to:
    • Sudden catecholamine withdrawal
    • Vasodilation and hypovolemia
  • Management:
    • Fluid boluses
    • Vasopressors: Norepinephrine, vasopressin
    • Steroids if bilateral adrenalectomy (prevent adrenal crisis)


๐Ÿงช Postoperative Concerns

  • Hypotension: Continue fluid support, vasopressors if needed
  • Hypoglycemia: Rebound insulin secretion โ†’ monitor glucose
  • Adrenal insufficiency: If bilateral adrenalectomy โ†’ lifelong steroids
  • Arrhythmias, pulmonary edema, residual hypertension
  • Pain control: IV paracetamol, opioids


โš ๏ธ Special Considerations

Pediatric pheochromocytoma:

  • Higher incidence of bilateral, extra-adrenal, familial syndromes

Pregnancy:

  • Rare, high maternal-fetal mortality if undiagnosed
  • Requires preoperative diagnosis and elective resection in 2nd trimester or cesarean + resection at delivery

MEN 2/3:

  • Also screen for medullary thyroid carcinoma, hyperparathyroidism


๐ŸŽฏ Viva Triggers

Question

Answer

Why alpha before beta blockade?

To avoid unopposed ฮฑ-adrenergic stimulation โ†’ hypertensive crisis

Role of metyrosine?

Inhibits tyrosine hydroxylase โ†’ โ†“ catecholamine synthesis

Preferred intra-op antihypertensive?

Nitroprusside, phentolamine, nicardipine

Post-tumor hypotension management?

Volume + norepinephrine

Signs of adrenal insufficiency post-op?

Hypotension, hyponatremia, hypoglycemia


โœ… MCQ Nuggets

  1. Drug contraindicated before alpha-blockade?
    โ†’ Beta-blockers
  2. Most sensitive test for pheochromocytoma?
    โ†’ Plasma free metanephrines
  3. Intraoperative BP spike after tumor handling โ€“ drug of choice?
    โ†’ Nitroprusside
  4. Drug used to inhibit catecholamine synthesis?
    โ†’ Metyrosine
  5. Post-resection persistent hypotension โ€“ initial management?
    โ†’ Volume replacement