What electrolyte imbalance should the nurse suspect in a client taking spironolactone who reports nausea and has peaked, narrow T-waves?

Spironolactone is a potassium-sparing diuretic that works by inhibiting aldosterone, which in turn promotes the retention of potassium in the kidneys. When a client taking spironolactone presents with symptoms such as nausea and peaked, narrow T-waves on an electrocardiogram (ECG), these clinical manifestations indicate a potential electrolyte imbalance, specifically hyperkalemia.

Peaked and narrow T-waves on an ECG are characteristic signs of elevated potassium levels in the blood. In this context, the combination of the diuretic medication, the reported symptoms, and the specific ECG changes strongly suggest that the client is experiencing an excess of potassium, which is commonly associated with the use of spironolactone.

Other options such as hyponatremia and hypernatremia relate to sodium levels and generally do not cause the specific ECG changes associated with hyperkalemia. Hypokalemia is also eliminated, as it would typically present with flattened or inverted T-waves instead of peaked ones. This combination of factors confirms that the most likely electrolyte imbalance in this scenario is indeed hyperkalemia.