Book 2, Case 4-Pheo, PONV Flashcards
How is diagnosis of pheochromocytoma made?
The measurement of free metanephrines in the plasma may be the
most reliable test for confmning the diagnosis. .urinary
metanephrines, and urinary vanillylmandelic acid.
Side note-dont’ palpate what in pheo?
H
Do not palpate the abdomen
Elevated Hct in pheo likely means:
suggestive of hypovolemia
Duration of alpha blockade prior to surgery:
When can it be discontinued?
While the optimal duration of a-blockade is unknown, most experts
recommend initiating blockade at least 10-14 days prior to surgery. This allows time
to stabilize the blood pressure
As for when it can be stopped: Some clinicians recommend discontinuing
a-blockade 24-48 hours prior to surgery or administering a half dose on the morning
of surgery to reduce the risk of significant hypotension following vascular isolation of
the tumor (abruptly stopping secretion of catecholamines).
How does a-Methylparatyrosine work? What are the side effects, and who is allowed to get it?
(a-Methyl tyrosine or metyrosine) inhibits the
rate-limiting enzyme, tyrosine hydroxylase, of the catecholamine synthetic pathway,
which results in a 40-80% reduction in catecholamine synthesis. Although this drug
is very effective, it is currently limited to patients with metastatic disease or those
requiring long term medical therapy (i.e. surgery is contraindicated) due to significant
side effects, including diarrhea, sedation, anxiety, depression, extrapyramidal
reactions, and crystalluria.
Why do pts have sudden hypotension after pheo is taken out?
Interruption of the vascular supply to the tumor results in
an abrupt cessation of catecholamine secretion from the tumor into the blood stream.
This reduction in circulating catecholamines combined with hypovolemia,
vasodilation from residual a-blockade, and cardiovascular depression from
anesthesia, can lead to significant hypotension.
Hypotension after pheo resection: how are you treating:
If hypotension did occur following
tumor resection, my initial treatment would be to ensure adequate volume
replacement with crystalloid or blood. If the hypotension were severe or persistent, I
would consider vasopressor therapy; if I suspected hypoadrenalism
Is it important to provide alpha blockade prior to beta-
Yes, because blockade of vasodilatory receptors could
result in unopposed vasoconstriction, hypertensive crisis, and congestive heart failure
due to the effects of excessive circulating catecholamines on a-receptors.
Pt with pheo has a decreased energy level-DDX
catecholamine induced cardiomyopathy/chf, or other cardiopulmonary issues
IF they ask you if you’ll given a fluid bolus in any pt-make sure what:
Now in terms of pheo
Make sure to say that you will perform an exam, assess volume status.
Now in terms of pheo, some are hypovolemic secondary to chronically increased SVR, and others are normovolemic-especially those on alphablockers
Remember!!!! If you’re in a situation where a PA could be helpful, but you don’t want to place one-you can always place a
TEE
How does pneumoperitoneum complicate PAC and CVP?
It can complicate the interpretation of central venous and pulmonadry artery pressure measurements-making them less reliable
What tube do you need to place for laparoscopy that you frequently forget to say:
OROGASTRIC OR NASOGASTRIC TUBE
What to avoid in pheo pts on induction and just period:
- avoid drugs that directly exacerbate effects of catecholamine excess
- avoid hypoxia and hypercarbia which can stimulate the sympathetic nervous system
Why no sux in pheo?
b/c sux can cause histamine release and/or abdominal fasciulations which can result in release of catecholamines from the tumor