Beta Blockers USMLE Step 1 Practice Question
A 70-year-old man with acute decompensated heart failure presents with dyspnea, orthopnea, and peripheral edema. Vital signs show BP 160/95 mmHg, HR 105/min, RR 22/min, and SpO2 88% on room air. He receives intravenous furosemide. Over several days, dyspnea improves, but he develops tinnitus and hearing loss. Labs reveal serum potassium 2.8 mEq/L, pH 7.52, and HCO3− 32 mEq/L. Chest X-ray shows improved pulmonary edema. Which mechanism best explains these adverse effects?
Answer choices
- AInhibition of carbonic anhydrase in proximal tubule
- BAntagonism of aldosterone receptor in collecting duct
- COsmotic retention of water in proximal tubule and descending limb
- DBlockade of Na Cl cotransporter in distal convoluted tubule
- EInhibition of Na K 2Cl cotransporter in thick ascending limbCorrect answer
- FInhibition of aquaporin-2 water channels in the collecting duct
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.