Problem: An older, female adult with coronary artery disease (CAD) and hypertension (HTN) was brought to the emergency department by her daughter, because of increasing weakness and confusion. The client was found by a neighbor. Wandering her neighborhood and unable to locate her home.. the client's daughter tells the nurse that her mother takes a water pill for her blood pressure to or three times a day the level on the medication bottle that she brought to the hospital states, hydrochlorothiazide. take one tablet daily. The client is admitted with flute volume deficit.. the nurse reviews the client admission lab test results which serum lab value requires follow up by the nurse?