Drug for management of hypertension in Phaeochromocytoma

Drug for management of hypertension in
a) Phenoxybenzamine
b) Phentolamine
c) Labetalol
d) Esmolol
Correct Answer - A
Ans. is ‘a’ i.e., Phenoxybenzamine
Once a pheochromocytoma is diagnosed, all patients should
undergo a resection of the pheochromocytoma following appropriate
medical preparation.
Resetting a pheochromocytoma is a high-risk surgical procedure
and an experienced surgeon/anesthesiologist team is required.
Some form of preoperative pharmacologic preparation is indicated
for all patients with catecholamine-secreting neoplasms.
Preoperative medical therapy is aimed at:
Controlling hypertension (including preventing a hypertensive crisis
during surgery) o Volume expansion
In patients with undiagnosed pheochromocytomas who undergo
surgery for other reasons (and who therefore have not undergone
preoperative medical therapy), surgical mortality rates are high due
to lethal hypertensive crises, malignant arrhythmias, and multiorgan
Combined alpha- and beta-adrenergic blockade
Combined alpha- and beta-adrenergic blockade is the most common
approach to control blood pressure and prevent intraoperative
hypertensive crises.
Alpha-adrenergic blockade
An alpha-adrenergic blocker is given 10 to 14 days preoperatively to
normalize blood pressure and expand the contracted blood volume.
Phenoxybenzamine is the preferred drug for preoperative
preparation to control blood pressure and arrhythmia in most centers
in the United States. It is an irreversible, long-acting, nonspecific
alpha-adrenergic blocking agent.
The initial dose is 10 mg once or twice daily, and the dose is
increased by 10 to 20 mg in divided doses every two to three days
as needed to control blood pressure and spells.
The final dose of phenoxybenzamine is typically between 20 and
100 mg daily.
Beta-adrenergic blockade
After adequate alpha-adrenergic blockade has been achieved, beta-
adrenergic blockade is initiated, which typically occurs two to three
days preoperatively.
The beta-adrenergic blocker should never be started first because
blockade of vasodilatory peripheral betaadrenergic receptors with
unopposed alpha-adrenergic receptor stimulation can lead to a
further elevation in blood pressure.
The alternatives to a and 13 adrenergic agents are calcium
channel blockers and metyrosine.
Calcium channel blockers
Although perioperative alpha-adrenergic blockade is widely
recommended, a second regimen that has been utilized involves the
administration of a calcium channel blocker.
Nicardipine is the most commonly used calcium channel blocker in
this setting; the starting dose is 30 mg twice daily of the sustained
release preparation.
Another approach involves the administration of metyrosine (alpha-
methyl Para-tyrosine), which inhibits catecholamine synthesis