The aim of this study is to investigate the continuous analgesic effect and side effects of ropivacaine combined with hydromorphone for combined spinal-epidural anesthesia(CSEA) after total knee arthroplasty and to explore its clinical application value. To observe whether hydromorphone combined with ropivacaine can promote the rapid recovery of patients.

For patients undergoing total knee arthroplasty, different spinal anesthesia drugs were injected in the two groups. The spinal anesthetic drugs injected in the hydromorphone group were hydromorphone 50 μg and ropivacaine 15 mg. In the control group, the spinal anesthetic was ropivacaine 15 mg.The differences in analgesia, sedation, and side effects between the hydromorphone group and the control group were analyzed by collecting various data at different times after anesthesia.

Inclusion Criteria:

• Age between 55 and 80 years old.
• ASA grade I to III.
• BMI:20-29kg/m2.
• No recent use of sedatives, opioids, or other analgesics.
• There was no contraindication of spinal anesthesia, severe dysfunction of heart, lung and other important organs or serious systemic diseases.
• Patients were willing to participate in the study and signed the informed consent.

Exclusion Criteria:

• The patient has mental illness or cannot cooperate with the completion of spinal anesthesia.
• The patient had a history of spinal surgery and spinal deformity.
• Patients had a history of opioid intolerance or adverse reactions.
• puncture site infection, coagulopathy or recent use of anticoagulant drugs.
• History of allergy to local anesthetics.
• Failed puncture.
• Unable to cooperate to complete the research process.

The participants, the surgeon, the surgical nurse, the data collector, and the anesthesiologist administering anesthesia were not aware of the patient groups