Final answer:
The priority for the nurse to assess in a client with a calcium level of 8.1 mg/dL is the cardiac rhythm.
Step-by-step explanation:
When assessing a client with a calcium level of 8.1 mg/dL, the priority for the nurse to assess is the cardiac rhythm. Calcium is essential for the normal excitability of heart muscle. Hypocalcemia can lead to problems with muscle contraction and nerve functioning, which can affect the heart's rhythm. Therefore, it is important for the nurse to prioritize assessing the cardiac rhythm in this situation.