Why shouldn we give propranolol to a patient with pheochromocytoma before her operation. I know pheochromocytoma is a catecholamine secreting tumor of the adrenal gland, so wouldn a strong beta-blocker help to neutralize this?
The main problem with pheochromocytoma is the high BP not the tachycardia. If a beta-blocker alone is given then you allow the alpha1-activity of the catecholamines to act unopposed. This would increase the BP still further. Beta-blockers can safely be given after the BP has been stabilized with an alpha-blocker. Labetalol (beta- and alpha-blocker) can be given alone to treat the crisis. Question: I have 2 questions: (1). When Isoproterenol is administered in the presence of Atropine, why isn’t HR elevated slightly more than the control due to removal of any vagal tone? (2). Why is pulse pressure increased in high doses of Epi Answer: (1). You are absolutely correct. Atropine would remove the vagal tone to the heart leading to a slight increase in heart rate that would be additive to the effect of ISO. This was academic and I wanted to avoid complicating a difficult area. (2). Changes in pulse pressure will reflect changes in cardiac contractility. EPI has increased this through action
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