Diuretics

A 58-year-old man with hypertension and chronic kidney disease (eGFR 35 mL/min/1.73m²) is prescribed a diuretic for fluid overload. Which is the most common adverse effect of loop diuretics in this patient?

A 72-year-old woman with heart failure (LVEF 35%) and hypertension is started on lisinopril and furosemide 40 mg daily. After 2 weeks, she develops severe muscle cramps, fatigue, and generalized weakness. Laboratory findings: Na⁺ 128 mEq/L, K⁺ 2.9 mEq/L, Cl⁻ 92 mEq/L, HCO₃⁻ 32 mEq/L. ECG shows U waves and flattened T waves. Which electrolyte abnormality is the primary driver of her symptoms, and what is the most appropriate next step?

A 58-year-old man with chronic heart failure (NYHA Class III) and hypertension is on lisinopril 10 mg daily and metoprolol 50 mg twice daily. His current medications include furosemide 40 mg daily. Recent labs show: serum K+ 5.8 mEq/L, serum creatinine 1.4 mg/dL, BUN 28 mg/dL. He reports persistent orthopnea and ankle edema. What is the most appropriate next step in management?

A 72-year-old woman with resistant hypertension (BP 168/98 mmHg despite amlodipine 10 mg, losartan 100 mg, and atenolol 50 mg daily) is found to have a serum sodium of 128 mEq/L and serum osmolality of 260 mOsm/kg. She denies polyuria or polydipsia. Physical examination shows no edema. What is the most appropriate next step?

Loop diuretics achieve their diuretic effect by blocking which ion transporter in the thick ascending limb of the loop of Henle?