00:01
The adrenal medulla is responsible
for catecholamine production.
00:05
Because we already covered this in the autonomic nervous
sytem section of pharmacology, we won't discuss it here.
00:16
There is one thing I want to mention however,
with respect to the adrenal medulla.
00:20
I want to talk about a cancer
or a lesion called pheochromocytoma.
00:26
Pheochromocytoma is a neuroendocrine tumour.
It is often found in the adrenal gland
but it can be found outside the adrenal gland as well.
00:35
It results in excess production of catecholamines,
mostly norepinephrine.
00:40
We can do all kinds of tests. One of the most easy and
simple test is the 24 hour metanephrine test of the urine.
00:47
We check for vanillylmandelic acid and metanephrines
as a routine in a 24 hour test,
but we can also do clinical testing and take a look at
patients' blood pressure and heart rate
and see that they tend to have very high levels.
01:02
Serum testing can also be done.
It is exceedingly expensive, but it's highly accurate.
01:07
I rarely have done serum testing on patients
when I'm diagnosing pheochromocytoma
we've actually made a diagnosis just with
the 24 hour urine and clinically,
and we've had actually managed to remove
successfully many pheochromocytomas.
01:23
Remember that plasma metanephrines can also be analyzed. We would
be looking specifically for normetanephrine and metanephrine.
01:32
Treatment of pheochromocytoma is invariably surgical.
We have to remove the tumour.
01:37
Now there are some pharmacological treatments that we
do utilize. These are not permanent treatment therapies.
01:43
These are just hold over treatment therapies
or bridge therapies.
01:46
Phenoxybenzamine, we've learnt about this drug in the CNS
lectures, is a nonspecific irreversible alpha blocker.
01:56
A short acting alpha blocker is prazosin.
We can also use terazocin as well.
02:03
Now, the other thing that we like to use is labetolol
which has combined alpha and beta blocker activity
to help us control the heart rate.
02:11
It's important that we never use a specific beta 1 blocker,
because when you give a beta 1 blocker to a patient with pheo,
you're gonna have unopposed alpha activity.
And for the purposes of the exams,
we're going to always say never use a specific beta 1 blocker.
02:30
In reality, sometimes we have, but I won't get into why,
and I want you to forget what I just said.
02:35
On your exam, never use a beta 1 blocker, remember that part.
02:40
Now, in terms of volume repletion,
remember that you want to give these patients fluids.
02:45
And sometimes we actually do something called
"salt loading" in some patients.
02:49
That's a specific issue
that we deal with in the pre-operative clinic.