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.