Afentanil and Remifentanil for Anesthesia Quality and Recovery

The goal of this clinical trial is to compare two commonly used opioid pain medications-alfentanil and remifentanil-during general anesthesia for surgery, and to find out whether alfentanil is as good as (not worse than) remifentanil in keeping patients stable (steady blood pressure and heart rate) and adequately pain-free during the operation. The study will enroll adults aged 18-65 years who are in good to fair health (ASA class I-III) and are scheduled for elective non-cardiac, non-brain surgery lasting 1 to 4 hours with expected blood loss under 500 mL. The main questions it aims to answer are: How often do patients need extra painkillers or blood-pressure medications during surgery (a "rescue event") when receiving alfentanil compared with remifentanil? How quickly do patients wake up, breathe on their own, and get discharged from the recovery room after the operation? Do patients experience differences in pain levels, nausea, vomiting, or thinking/memory problems in the days after surgery? If there is a comparison group: Researchers will compare the alfentanil group with the remifentanil group to see if the rate of rescue events with alfentanil is not more than 8% higher than with remifentanil (the non-inferiority margin). Both groups will receive the same standard anesthetic (propofol and muscle relaxants) and the same postoperative pain management; only the study opioid differs. Participants will: Sign an informed consent form and undergo screening tests, including blood work, physical exam, and medical history review. Be randomly assigned (like a coin flip) to receive either alfentanil or remifentanil during their operation, with the drug given through an IV. Neither the patient nor the care team will know which drug is given until after the study is completed. Have their blood pressure, heart rate, breathing, and brain activity (using BIS monitors to measure depth of anesthesia) continuously tracked during surgery. After surgery, be followed for up to 3 days, during which they will be asked to rate their pain (using a simple 0-10 scale) and complete a short memory/thinking test (MMSE) at set times. Provide small blood samples before, right after, and 24 hours after surgery to measure stress hormones and inflammation markers. This study will involve about 990 patients across multiple hospitals and will take about 2 years to complete. The results will help doctors choose the best opioid for safer, smoother surgeries and faster recovery.