Comparison of patient-controlled analgesia with background opioid versus non-opioid infusion for postoperative pain in patients undergoing total knee arthroplasty

INTERVENTION: Drug : Patients who undergoing total knee arthroplasty under spinal analgesia will be recruited and randomly assigned to the following two groups according to the regimen of PCA: (A) opioid group who receive only fentanyl citrate 1200mcg for continuous infusion drug, (B) non‐opioid group who receive ketorolac tromethamine 150mg with nefopam hydrochloride 100mg for continuous infusion drug. All the patients will receive additional fentanyl citrate as bolus injection drug if they need more analgesics postoperatively. The primary outcome is the pain score evaluated by visual analogue scale 24 hours after the surgery. The secondary outcomes are the total amount of drugs infused for postoperative pain control, additionally injected dose of fentanyl, pain score evaluated while they walk, and rest till 48 hours after the surgery. Antiemetics required due to nausea or vomiting will be also recorded. Other discomfort patients complained, and complications due to drugs will be treated and recorded. CONDITION: Diseases of the musculoskeletal system and connective tissue PRIMARY OUTCOME: The primary outcome is the pain score evaluated by visual analogue scale 24 hours after the surgery. SECONDARY OUTCOME: the total amount of drugs infused for postoperative pain control INCLUSION CRITERIA: We will enrolled patients aged 60‐78 years with ASA physical status I–II, and undergoing elective total knee arthroplasty under spinal anesthesia.