Final answer:
When a patient is taking Meperidine (Demerol) for pain after hip arthroplasty, it's essential to monitor their urine output to prevent renal complications.
Step-by-step explanation:
After a patient has undergone hip arthroplasty and is prescribed Meperidine, also known as Demerol, for pain control, it is essential for healthcare providers to monitor certain vital signs to ensure the patient's safety. Meperidine is both an analgesic, which reduces pain without loss of consciousness, and a narcotic, which can cause drowsiness and loss of consciousness at higher doses. Therefore, the most critical parameter to monitor during this time is urine output. This is because narcotics like Meperidine can affect renal function and the patient's ability to urinate, which could potentially lead to urinary retention or other significant complications.