A client with metastatic cancer who was taking hydromorphone PO at home is now receiving the medication IV while in the hospital. To evaluate if the client is receiving an equianalgesic dose of the hydromorphone, which assessment should the nurse complete?

A. Assessing the level of consciousness is important for monitoring sedation but does not directly measure pain control. B. Monitoring respiratory rate is crucial for safety with opioid use, but it does not assess the effectiveness of pain relief. C. Blood pressure may vary with pain levels but is not a direct measure of the effectiveness of analgesia. D. Assessing the pain scale is essential to determine if the client is experiencing adequate pain relief with the current dose of hydromorphone, ensuring that the equianalgesic dosing is effective.