[Pheochromocytoma]

0.1-0.2% of all cases of hypertension are caused by pheochromocytomas, or catecholamine-producing tumors derived from chromaffin tissue. The occurrence of combined symptoms of paroxysmal headache, sweating, and hypertension is probably a more sensitive and specific indicator than any one biochemical test for pheochromocytoma. Alpha-adrenergic receptor blockade with prazosin or doxazosin has been administered to restore plasma volume by counteracting the vasoconstrictive effects of high levels of catecholamines. Virtually all anesthetic drugs and techniques (including isoflurane, sevoflurane, remifentanil, fentanyl, and regional anesthesia) have been used with success. For intraoperative hypertension various drugs have been used and for hypotension noradrenaline, dopamine, dobutamine, and adrenaline have been used. 25-50% of hospital deaths in patients with pheochromocytoma occur during induction of anesthesia or during operative procedures for other causes. Adrenergic receptor blocking drugs probably reduce the complications of hypertensive crisis, the wide BP fluctuations during manipulation of the tumor (especially until venous drainage is obliterated), and the myocardial dysfunction that occurs perioperatively. A reduction in mortality associated with resection of pheochromocytoma (from 40% to 60% to the current 0% to 6%) occurred when alpha-adrenergic receptor blockade was introduced as preoperative preparatory therapy.