Pheochromocytoma= A rare catecholamine producing tumour that originate from chromaffin cells in the adrenal medulla. Patients classically present with: paroxysmal hypertension, palpitations, headache, and diaphoresis. The frequency varies from daily, weekly or monthly. Patients generally have orthostatic hypotension on physical exam.
NOTE: Surgery is the definitive treatment. Pre-operatively the patient must be given both alpha- AND beta-blocking agents!
Beta-blocker= opposes the subsequent reflex tachycardia secondary to alpha-blockade
WARNING: Never give a patient with a pheochromocytoma a beta-blocker without first giving an alpha-blocker!!!
WHY? Epinephrine and Norepinephrine released by the adrenal medulla act on both alpha & beta receptors. In the absence of beta-2-mediated vasodilation, profound unopposed alpha-mediated vasoconstriction may lead to hypertensive crisis or pulmonary edema.
Use: phenoxybenzamine beforehand or consider Labetalol (mixed alpha/beta adrenergic antagonist)
Chapter 23: Hypertension. Symptom to Diagnosis: An Evidence-Based Guide, 3e
Myklejord DJ. Undiagnosed Pheochromocytoma: The Anesthesiologist Nightmare. Clinical Medicine and Research. 2004;2(1):59-62.