Autonomic Pharmacology USMLE Step 1 Practice Question
A 55-year-old man with a 10-year history of COPD presents to the emergency department with acute-onset wheezing, dyspnea, and chest tightness. Vital signs are BP 210/130 mmHg, HR 138 bpm, RR 26/min, and SpO2 79%. On examination, he has diffuse bilateral wheezing and appears diaphoretic and anxious. The medical team administers intravenous epinephrine for presumed bronchospasm. Within 10 minutes, his blood pressure rises to 280/160 mmHg, he develops severe substernal chest pain radiating to the left arm, and his electrocardiogram shows ST-segment depression in the precordial leads. His troponin I is elevated at 0.08 ng/mL. Laboratory studies reveal plasma free metanephrines of 4.8 nmol/L (normal <0.9 nmol/L). Which of the following best explains the acute clinical deterioration following epinephrine administration?
Answer choices
- AUnopposed alpha-adrenergic vasoconstriction in a patient with undiagnosed pheochromocytomaCorrect answer
- BBeta-2 adrenergic receptor desensitization from chronic bronchodilator use in COPD
- CDirect myocardial depression from excessive catecholamine exposure
- DActivation of muscarinic receptors causing coronary artery vasospasm
- EInhibition of phosphodiesterase leading to excessive cAMP accumulation
- FParasympathetic rebound phenomenon following sympathomimetic administration
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