A 45-year-old man presents with sudden severe headache, profuse diaphoresis, and palpitations. Vital signs: BP 220/140 mmHg, HR 118/min, RR 16/min, Temp 37.2°C. Labs show elevated plasma free metanephrines (1,200 pg/mL; normal <90). CT abdomen reveals a 3-cm right adrenal mass. He denies chest pain. Prior to surgical removal, he receives phentolamine followed by propranolol. Why is this sequential drug administration order critical for patient safety?
- A)The order is irrelevant if both drugs are given before surgery
- B)Propranolol must precede phentolamine to prevent tachycardia
- C)Propranolol potentiates phentolamine's hypotensive effect
- D)Phentolamine must precede propranolol to prevent unopposed alpha effectsGABARITO
- E)Phentolamine causes reflex tachycardia that propranolol prevents when given first
Explicação
Phentolamine (alpha blocker) must be given first to block vascular alpha-1 receptors and prevent hypertensive crisis. Propranolol (beta blocker) is then added to control reflex tachycardia caused by phentolamine's vasodilation. If propranolol were given first ... Ver explicação completa e trilha adaptativa →