Which electrolyte requires monitoring due to diuretic and RAAS therapy?

• A. Sodium
• B. Potassium
• C. Calcium
• D. Magnesium

Answer: (B)

Potassium is the electrolyte to monitor because diuretics, especially loop and thiazide types, increase potassium loss, while RAAS therapies (ACE inhibitors, ARBs, and particularly aldosterone antagonists like spironolactone or eplerenone) promote potassium retention. In heart failure care, patients are commonly on both diuretics to relieve fluid overload and RAAS inhibitors to improve outcomes, which can push potassium levels in opposite directions. This interplay makes potassium balance the most critical to watch to prevent dangerous arrhythmias or severe electrolyte disturbances. Sodium, calcium, and magnesium can be affected too, but the combination of diuretic-induced loss and RAAS-mediated retention most directly targets potassium. Regular monitoring of potassium helps guide dose adjustments and safeguard the patient.