A patient with chronic kidney disease is experiencing hyperkalemia. What nursing intervention should be implemented first?

Hyperkalemia is elevated serum potassium >5.0 mmol/L causing membrane excitability alterations, cardiac conduction abnormalities, risk of arrhythmias, and neuromuscular dysfunction. Severe levels ≥6.5 mmol/L produce peaked T waves, widened QRS complexes, ventricular dysrhythmias, and potential cardiac arrest. Rationale: A. Administering a potassium-wasting diuretic promotes renal excretion of potassium, but its effect is not immediate. In chronic kidney disease, reduced renal function limits efficacy. It does not address urgent cardiac instability risk associated with elevated potassium levels. B. Encouraging avoidance of potassium-rich foods is a long-term management strategy for chronic hyperkalemia. It does not provide rapid correction of dangerously elevated potassium levels. Immediate intervention must prioritize prevention of life-threatening arrhythmias rather than dietary modification. C. Sodium polystyrene sulfonate removes potassium via gastrointestinal exchange, but onset is delayed over hours. It is useful for lowering potassium levels but not for immediate stabilization. It does not directly protect against acute cardiac effects of hyperkalemia. D. Initiating cardiac monitoring is the priority because hyperkalemia can precipitate fatal arrhythmias. Continuous ECG allows early detection of conduction abnormalities such as peaked T waves and widened QRS complexes. This enables prompt intervention to prevent cardiac arrest and deterioration.