Which electrolyte abnormality is most concerning in CKD and can cause arrhythmias?

• A. Hyperkalemia
• B. Hyponatremia
• C. Hypercalcemia
• D. Hypophosphatemia

Answer: (A)

Elevated potassium is the most concerning in CKD because the kidneys normally excrete potassium, and CKD severely impairs that excretion. Potassium sets the heart’s resting membrane potential and helps control repolarization. When extracellular potassium rises, the resting membrane potential becomes less negative, inactivates fast sodium channels, and slows conduction through the heart. This creates a high risk for dangerous rhythm disturbances, including wide QRS, peaked T waves progressing to ventricular arrhythmias and even cardiac arrest if not treated promptly.

In CKD, factors like metabolic acidosis and reduced renal excretion worsen potassium buildup, making hyperkalemia particularly dangerous. Other abnormalities can cause problems, but they’re less immediately life-threatening in this context.