Q Which of the following regimens is best for the pre-operative management of a patient with pheochromocytoma?
Propranolol alone
Propranolol followed by phenoxy-benzamine
Prazosin
Phenoxy-benzamine followed by propranolol
According to Harrison 17th ed "complete tumor removal is the ultimate therapeutic goal".
Preoperative patient preparation is essential for safe surgery.
alpha adrenergic blocker (phenoxybenzamine) should be initiated at relatively low doses (eg-5-10mg orally three times per day) and increased as tolerated every few days.
Because patients are volume constricted, liberal salt intake & hydration are necessary to avoid orthostasis.
Adequate alpha blockade generally requires 10-14 days, with a typical final dose of 20-30 mg phenoxybenzamine three times per day.
Oral prazosin or iv. phentolamine can be used to manage paroxysms while awaiting alpha blockade.
Before surgery, the blood pressure should be consistently below 160/90 mm Hg, with modertae orthostasis.
Beta blockers (eg 10mg propranolol three to four times per day) can be added after starting alpha blockers, and increased as needed, if tachycardia persists.
Because beta blockers can induce a paradoxical increase in blood pressure in the absence of alpha blockade, they should be administered only after effective alpha blockade.
Other antihypertensives, such as calcium-channel blockers or angiotensin-converting enzyme inhibitors, have also been used when blood pressure is difficult to control with phenoxybenzamine alone.