The nurse is admitting a client with a history of heart failure who takes losartan and spironolactone. The client has been experiencing heart palpitations. The 12 lead EKG shows tall, peaked T-waves and flat P-waves. Which of the following lab results corresponds to these findings?

Choice A rationale Sodium 135 mEq/L is within the expected reference range, which is typically 135 to 145 mEq/L. Hypernatremia or hyponatremia are not indicated by this value, and it does not directly explain the characteristic EKG changes of tall, peaked T-waves and flat P-waves which are pathognomonic for severe hyperkalemia. Normal serum sodium levels would typically not cause cardiac excitability alterations resulting in such significant EKG findings. Choice B rationale B-type Natriuretic Peptide (BNP) 560 pg/mL is an elevated value, indicating fluid volume overload and stretching of the ventricles, consistent with the client's history of heart failure. However, while elevated BNP is a marker of heart failure severity, it does not directly cause the specific EKG findings of tall, peaked T-waves and flat P-waves, which are related to electrolyte imbalances affecting cardiac repolarization and depolarization. Choice C rationale Potassium 7.0 mEq/L is significantly elevated (hyperkalemia), as the normal range is 3.5 to 5.0 mEq/L. Hyperkalemia is a serious side effect of potassium-sparing diuretics like spironolactone and is exacerbated by ACE inhibitors or ARBs like losartan. Severe hyperkalemia interferes with myocardial repolarization, causing tall, peaked T-waves, shortened QT interval, and progressive slowing of impulse conduction, leading to flat P-waves and a wide QRS complex. Choice D rationale Blood Urea Nitrogen (BUN) 52 mg/dL is elevated, as the normal range is approximately 10 to 20 mg/dL. An elevated BUN suggests dehydration or impaired renal function, which can be seen in heart failure. Impaired kidney function could contribute to electrolyte imbalance, but the elevated BUN itself is a reflection of renal impairment, not the direct cause of the specific EKG changes observed, which are strongly indicative of hyperkalemia.