Pheochromocytoma & B-blocker

[Reperfused]

Why do we give B-blockers in pheochromocytoma?

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[Saxappeal1]

Im pretty sure it is to treat the primary hypertension caused by the pheochromocytoma, but other members please feel free to correct me, I just remember that from class. The alpha blocker would be used specifically to counter the excess catecholamines and decrease vascular resistance and the beta blockers like propranolol would be used to control the rate.

 

[jqueb29]

Im pretty sure it is to treat the primary hypertension caused by the pheochromocytoma, but other members please feel free to correct me, I just remember that from class. The alpha blocker would be used specifically to counter the excess catecholamines and decrease vascular resistance and the beta blockers like propranolol would be used to control the rate.

The beta blocker by itself would actually cause unopposed alpha action and severe hypertension. Beta is given for heart rate control after alpha blockade has kicked in.

 

[Saxappeal1]

Of course you wouldn't want to only use a beta blocker, you would get severe hypertension

 

[Reperfused]

Yeah I know the first thing we do is give a-blocker to control hypertension.
ok so B-blocker to control other effects like tachycardia.
It was so easy, gosh! I guess I was brain dead while asking this qs lol. Obviously once NE & Epi are released they're gonna act on alpha & beta receptors both.
Thanks guys!

 

[Saxappeal1]

Yeah beta blockers like propranolol are used as rate control to control rebound tachycardia caused by the alpha blockers used to treat the pheochromocytoma

 

[Phloston]

If you want to kill your patient, give a beta-blocker in pheochromocytoma.

The answer is always phenoxybenzamine (irreversible alpha-blocker) as first-line.

Only after you've alpha-blocked can you give a beta-blocker. As above poster has mentioned, if you beta-block first you'll get unopposed alpha agonism, which is all of your catecholamines binding to alpha receptors instead --> massive arteriolar vasoconstriction --> severe worsening of HTN.

This question is HY for Steps 1,2 and 3, and there were still people (like 12%) getting this wrong in UWorld Step 3 when I went through that QBank. Which means 1 in 8 of doctors would have killed their pheo patient.

 

[Saxappeal1]

Well now we will never forget it. Thanks for that explanation Phloston!

 

[DrPicard]

As far as I understand, with pheo giving a beta blocker unmasks the alpha receptors --> HTN worsens.

Same idea applies to cocaine.

With aortic dissection, giving an alpha blocker (or any vasodilator) first will cause a reflex increase in sympathetic activity to the heart --> more shear forces working to expand the dissection. Hence beta blocker first in this case.