A nurse is caring for a client who has a serum potassium level of 5.5 mEq/L. The provider prescribes polystyrene sulfonate. Which of the following ECG results should indicate to the nurse that the medication has been effective?

Rationale: A. Widening of the QRS complex is associated with severe hyperkalemia, not with improvement. B. Reduction in P wave duration is not a typical indicator of potassium normalization. C. Restoration of QRS amplitude is not a reliable or specific indicator of potassium correction. D. A tall, peaked T wave is a classic ECG sign of hyperkalemia. A reduction in T wave amplitude suggests that serum potassium levels are returning to normal, indicating the effectiveness of polystyrene sulfonate, which works to lower potassium levels.