Pheochromocytoma resection

🔬 Pathophysiology - Hormone Havoc Headquarters

• Origin: Tumor of chromaffin cells (neuroectodermal crest origin) located in the adrenal medulla.
• Secretion: Produces, stores, and secretes catecholamines (norepinephrine, epinephrine) in an unregulated, episodic manner.
• Synthesis: Tyrosine → DOPA → Dopamine → Norepinephrine → Epinephrine.
  • The final step, NE → Epi, is catalyzed by Phenylethanolamine-N-methyltransferase (PNMT).
• Metabolism: Catecholamines are degraded to metanephrines and vanillylmandelic acid (VMA), which are measured for diagnosis.

⭐ 📌 Rule of 10s: A classic mnemonic stating 10% of pheochromocytomas are:

• Malignant
• Bilateral
• Extra-adrenal
• In children
• Calcified

🚨 Clinical Manifestations - The Catecholamine Crisis

• Caused by episodic surges of catecholamines (epinephrine, norepinephrine), leading to paroxysmal symptoms.
• 📌 Classic Triad (PHEochromocytoma):
  • Palpitations & Tachycardia
  • Headache (severe, throbbing)
  • Episodic sweating (profuse diaphoresis)
• Severe hypertension is the hallmark; can be sustained or paroxysmal and often resistant to standard therapy.
• Other symptoms include anxiety, panic attacks, tremor, pallor (vasoconstriction), and chest/abdominal pain.
• ⚠️ Triggers: Anesthesia induction, surgery, childbirth, certain drugs (e.g., TCAs, metoclopramide).

⭐ Catecholamine excess can cause severe, reversible LV dysfunction (catecholamine-induced cardiomyopathy), mimicking myocardial infarction or Takotsubo cardiomyopathy.

🔬 Diagnosis - Finding the Pheo

• Biochemical Confirmation (Step 1):

  • Best initial test: Plasma free metanephrines (Sensitivity >95%).
  • Confirmatory: 24-hour urine for fractionated metanephrines & catecholamines.
  • ⚠️ Avoid interfering meds (e.g., TCAs, levodopa, decongestants).

• Localization (Step 2 - after biochemical proof):

  • First-line: CT or MRI of abdomen/pelvis.
  • If negative, extra-adrenal, or metastatic suspicion: Functional imaging (e.g., MIBG scan, Ga-DOTATATE PET/CT).

⭐ Clonidine Suppression Test: Used for borderline cases. In pheochromocytoma, autonomous tumor secretion means plasma catecholamines are NOT suppressed by clonidine (an α2-agonist).

💊 Management - Taming the Tumor

Pre-operative preparation is crucial to prevent intraoperative hypertensive crisis. The goal is to "tame" the tumor's catecholamine effects before resection.

• Pharmacologic Blockade:
  • Step 1: α-Blockade (start 10-14 days pre-op)
    • Phenoxybenzamine (irreversible, non-selective) is classic.
    • Selective α1-blockers (Doxazosin, Prazosin) are alternatives with fewer side effects.
    • Titrate to BP <130/80 mmHg seated, with mild orthostasis (systolic >90 mmHg standing).
  • Step 2: β-Blockade (start 2-3 days after α-blockade)
    • Add only AFTER adequate α-blockade to control reflex tachycardia.
    • e.g., Propranolol, Metoprolol.
  • Step 3: Volume Expansion
    • Liberal salt intake and IV fluids to counteract catecholamine-induced volume contraction and prevent post-op hypotension.

⭐ Alpha-blockade FIRST, then Beta-blockade. Unopposed alpha-stimulation from beta-blockade alone (blocking vasodilatory β2 receptors) can lead to a life-threatening hypertensive crisis.

Pre-Op Blockade Sequence:

• Intra-operative:
  • Hypertension: IV Nitroprusside, Phentolamine.
  • Hypotension: After adrenal vein ligation, treat with fluids & pressors.

⚡ High-Yield Points - Biggest Takeaways

• Pre-op alpha-blockade (e.g., phenoxybenzamine) for 10-14 days is ESSENTIAL to prevent hypertensive crisis.
• Add beta-blockade ONLY AFTER adequate alpha-blockade to avoid unopposed alpha-stimulation and hypertensive crisis.
• Liberal IV fluids are required pre-op to expand volume and prevent post-resection hypotension.
• Manage intra-op hypertension with short-acting agents like nitroprusside or phentolamine.
• Anticipate post-op hypotension from catecholamine withdrawal; treat with fluids/pressors.
• Screen for associated syndromes: MEN 2A/2B, VHL, NF1.