Average Age at Time of Diagnosis: 47 y/o (J Am Coll Surg, 2009) [MEDLINE]
Physiology
Mechanisms
Catecholamine Secretion by Pheochromocytoma
Dopamine
Epinephrine
Norepinephrine
Increased Central Sympathetic Activity: may play a role
Physiologic Effects
α-Adrenergic Effects
Vasoconstriction
β-Adrenergic Effects
Tachycardia
Vasodilation
Inhibition of Renin-Agiotensin-Aldosterone Axis
Plasma Volume Contraction
Malignant Pheochromocytoma
Approximately 10% of All Catecholamine-Secreting Tumors (Pheochromocytomas and Catecholamine-Secreting Paragangliomas) are Malignant
Malignancy is Only Manifested by Local Invasion or Distant Metastases: metastases can occur as long as 20 yrs after resection of the primary malignant tumor
Approximately 50% of Cases Have Paroxysmal Hypertension
Approximately 35-45% of Cases Have Primary Hypertension (Which Presents Similarly to Essential Hypertension): these patients may also manifesta paroxysmal symptoms
Approximately 5-15% of Cases are Normotensive: the frequency of normotension is higher in cases with adrenal incidentalomas or those diagnosed through familial screening
Paroxysmal Hypertension/Tachycardia/Arrhythmia May Occur During Procedures (Colonoscopy, etc), After Induction of General Anesthesia, After Eating Foods/Beverages Containing Tyramine, or with Specific Medications (Metoclopramide, Monoamine Oxidase Inhibitors)
Orthostatic/Episodic Hypotension (see Hypotension)
Epidemiology: occurs in some cases
Clinical Patterns
Episodic Hypotension: in rare cases where the tumor secretes only epinephrine
Pattern of Rapid Cyclic Fluctuation Between Hypertension and Hypotension (Cycling Every 7-15 min): unclear mechanism
Orthostatic Hypotension: due predominantly to decreased plasma volume
Normalizes Blood Pressure and Expands the Contracted Plasma Volume
Dose: start 10 mg PO qday-BID, then increase by 10-20 mg qday (in divided doses) every 2-3 days to control blood pressure and episodic symptoms
Start 14 Days Preoperatively: longer preoperative lead time is required in patients with recent myocardial infarction, catecholamine cardiomyopathy, refractory hypertension, or catecholamine-induced vasculitis
Monitor Blood Pressure Closely: general target BP <120/80 (sitting) with SBP >90 (standing)
Dose: start low dose, titrating up gradually to control tachycardia (goal heart rate: 60-80)
Start Only After α-Blockade Has Been Achieved: usually 2-3 days preoperatively
Never Start Prior to α-Blockade, Due to the Potential to Precipitate Worsening Hypertension
May Be Contraindicated in Patients with Congestive Heart Failure or Asthma/COPD
Alternative Regimens
Calcium Channel Blockers (see Calcium Channel Blockers): may be used as a supplement to the above regimen or as a substitute for patients with intolerable side effects from α-blocker therapy
