A patient undergoing pheochromocytoma resection develops severe hypertension after tumor manipulation. The anesthesiologist administers phentolamine IV. What is the most important reason that a beta-blocker should NOT be administered first in this setting?
- A Beta-blockers directly stimulate catecholamine release from the tumor
- B Beta-blockers decrease renal clearance of epinephrine
- C Beta-blockers cause paradoxical increase in blood pressure by unopposed alpha stimulation ✓
- D Beta-blockers competitively displace phentolamine from alpha receptors
Correct answer: C. Beta-blockers cause paradoxical increase in blood pressure by unopposed alpha stimulation
Explanation
Pheochromocytoma secretes both epinephrine and norepinephrine. If a beta-blocker is given first without adequate alpha-blockade, the beta-mediated vasodilation is blocked while alpha-1 vasoconstriction remains unopposed, leading to a dangerous paradoxical hypertension. Alpha-blockade must always precede beta-blockade in pheochromocytoma management.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.