Final answer:
Before administering captopril to a patient with CKD, the nurse must check potassium levels as it can be affected by this medication. Serum creatinine should also be monitored to evaluate kidney function.
Step-by-step explanation:
Before administering captopril (Capoten) to a patient with stage 2 chronic kidney disease (CKD), the nurse should check the patient's potassium levels. Captopril is an ACE inhibitor that can potentially increase potassium levels, which is critical information for patient safety, particularly in those with CKD where potassium levels can already be compromised. Along with potassium, the nurse should also monitor serum creatinine to assess kidney function and the effects of the medication on the kidneys.