A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 65-year-old woman with a history of hypertension and heart failure presents to the clinic with muscle cramps and palpitations. She has been taking furosemide and spironolactone for the past six months. Her blood pressure is 132/84 mmHg, pulse is 78/min, and respirations are 16/min. Laboratory studies show a serum potassium level of 3.2 mEq/L and serum magnesium level of 1.1 mg/dL. ECG reveals flattened T waves. Which of the following is the most appropriate next step in the management of this patient?
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A
Administer intravenous potassium chlorideIncorrect. IV KCl is reserved for severe hypokalemia or symptomatic ECG changes; it isn't indicated at this potassium level.
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B
Discontinue spironolactoneIncorrect. Spironolactone is potassium-sparing, so discontinuing it would worsen renal potassium loss and the existing hypokalemia.
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C
Perform a 24-hour urine potassium testIncorrect. A 24-hour urine test isn't urgently needed; magnesium correction is the immediate priority to enable K repletion.
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D
Increase furosemide doseIncorrect. Increasing furosemide would worsen both hypokalemia and hypomagnesemia by enhancing distal tubular electrolyte losses further.
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E
Initiate oral magnesium supplementationCorrect. Hypomagnesemia perpetuates renal potassium wasting via ROMK; magnesium repletion enables effective potassium correction.
↑ Tap an answer to reveal the reasoning
Answer: E. The patient presents with hypokalemia and hypomagnesemia, likely due to diuretic use. Hypomagnesemia can exacerbate hypokalemia due to increased renal potassium loss. The most appropriate next step is to correct the magnesium deficiency, which will help normalize the potassium levels. Increasing the furosemide dose or discontinuing spironolactone would worsen the hypokalemia. Intravenous potassium chloride is not indicated first-line in the absence of severe symptoms or ECG changes. A 24-hour urine test is not immediately necessary before correcting hypomagnesemia.