When starting RAAS inhibitors in heart failure, which monitoring parameter should be prioritized to prevent electrolyte disturbances?

• A. Urine microalbumin
• B. Serum potassium
• C. White blood cell count
• D. Platelet count

Answer: (B)

Potassium monitoring is the priority when starting RAAS inhibitors because these drugs raise potassium levels by reducing aldosterone-driven potassium excretion in the kidneys. In heart failure, preventing hyperkalemia is crucial, especially in patients with kidney impairment, diabetes, the elderly, or those taking other potassium-sparing agents. Check potassium soon after initiation or uptitration (often within the first week), then repeat periodically as therapy continues. If potassium climbs toward or above a safe limit (commonly around 5.5 mmol/L or higher, depending on guidelines and individual risk), adjust the regimen—lower the dose, hold, or switch medications—and reassess. While kidney function and urine albumin give important context, the electrolyte disturbance most directly prevented by monitoring is hyperkalemia, making serum potassium the essential parameter to track.