Pheochromocytoma Flashcards
are basically modified postganglionic nerves that lack axons and secrete their neurotransmitter (mainly epinephrine) directly into the blood; thus, the bloodstream acts like a giant synapse, carrying epinephrine to receptors throughout the body.
Adrenal medullary (chromaffin) cells
are tumors of the chromaffin cells of the adrenal medulla
Pheochromocytoma
are tumors that arise from extra-adrenal ganglia of the sympathetic nervous system.
Paragangliomas
Pheochromocytomas can secrete excessive amounts of both ___________, whereas paragangliomas and metastases of pheochromocytomas generally secrete primarily_____
epinephrine and norepinephrine
norepinephrine
What is our RLS in formation of epi and norepi
tyrosine hyroxylase
What is expressed more in the adrenall medulla then sympathetic nerves so that Nepi is our primary product of SNS while Epi is the primary product from adrenal medulla?
PNMT
What is the cause of our manifestation of symptoms from pheochromocytomas?
catecholamie excess
***see Fight or Flight type sytmpoms
The classic symptoms of pheochromocytomas are
hypertension (90% of patients),
headaches (80%),
diaphoresis (70%),
and palpitation (60%).
These symptoms are mediated by catecholamine excess.
Patients who undergo removal of pheochromocytomas are usually _____ and need large amounts of fluid to compensate when the offending lesion is removed and catecholamine levels fall rapidly.
volume constricted
You suspect pt has pheochromocytoma, what 24 hr URINARY test would you order?
Catecholamines
You suspect pt has pheochromocytoma, what PLASMA test do you order?
Free metanaphrines
slightly more sensitive the catecholamine test
Only after biochemical confirmation of a pheochromocytoma is secured should imaging be obtained to locate the causative lesion. The best imaging test is
CT scan of the abdomen/adrenal glands.
If CT is not able to identify a causative lesion or there is question about a lesion what other functional imaging can be used?
MIBG scanning uses 131Iodine tagged MIBG (iodine-131-meta-iodobenzylguanidine) to identify pheochromocytomas.
WHy can we use an octreotide scan do dx pheochromocytoma?
they occasionally express somatostain receptors
The only curative therapy for pheochromocytoma is
surgical removal of the tumor. Unilateral adrenalectomy of the effected gland is the preferred therapy.
What is dangerous about removing a pheochromocytoma?
During surgical removal of a pheochromocytoma the manipulation of the tumor can cause release of excessive amounts of catecholamines. This surge in catecholamines can cause profound vasoconstriction and resultant hypertensive emergency.
During surgical removal of a pheochromocytoma the manipulation of the tumor can cause release of excessive amounts of catecholamines. This surge in catecholamines can cause profound vasoconstriction and resultant hypertensive emergency, how can we appropriately prep pts?
should be treated with alpha-adrenergic blockers so that catecholamine induced vasoconstriction is prevented.
is a nonselective alpha blocker with a long half-life of about 24 hours. It does not block the synthesis of catecholamines; in fact, the synthesis of catecholamines and metanephrines tends to increase during alpha blockade.
Phenoxybenzamine
synthesis of catecholamines and metanephrines tends to increase during alpha blockade thus patients should be treated with alpha blockers until they are
normotensive or develop orthostasis
Therapy with alpha blockers tends to increase the heart rate so after appropriate alpha blockade is achieved _______ should be used to help decrease tachycardia
beta-adrenergic blockade
