This study evaluates postoperative numerical pain score and systemic opioid requirement within 48 hours for unilateral total knee arthroplasty. Comparing among 3 groups of intrathecal morphine; 0,50, 100 ug with multimodal analgesia.

Intrathecal opioid is effective postoperative analgesia for orthopedic lower extremity surgery. However there are some limitations such as nausea, vomiting, pruritus, dizziness. Nowadays multimodal analgesia is used in unilateral total knee arthroplasty include oral analgesic drugs, adductor canal block and local analgesia infiltration.

This study evaluates whether intrathecal opioid should be added in the role of multimodal analgesia in total knee arthroplasty.

Inclusion Criteria:

• Aged more than 18 years old undergoing unilateral total knee arthroplasty
• American Society of Anesthesiologists physical status classification 1-3

Exclusion Criteria:

• Participants deny to enroll the study
• Allergy to local anesthetics, opioid and NSAIDs
• Hepatic disease
• Contraindication for neuraxial block or adductor canal block
• Uncontrolled cardiovascular disease
• Creatinine clearance less than 50 ml/min

In the anesthetic record, 0.5% isobaric bupivacaine with study drug is recorded.