Study on the minimum effective dose of Oliceridine in PCIA combined with iliofascial block block for analgesia after knee arthroplasty

INTERVENTION: iliac fascia block with Oliceridine:Ultrasound‐guided fascia iliaca compartment block (FICB) was performed using 20 mL of 0.15% ropivacaine, followed by total knee arthroplasty under combined spinal‐epidural anesthesia (CSEA). At the end of surgery, oliceridine 20 mg was diluted with 80 mL normal saline to a total volume of 100 mL for patient‐controlled intravenous analgesia (PCIA). The PCIA regimen was set as: loading dose 5 mL, background infusion rate 2 mL/h, bolus PCA dose 2 mL, lockout interval 15 minutes. Postoperative visual analogue scale (VAS) pain scores were recorded at 12 h, 24 h, 36 h and 48 h after surgery. If the VAS score at all four time points was =4, the administered oliceridine dose was defined as an effective dose. The per‐kilogram oliceridine consumption for the patient was calculated (e.g., for a patient weighing 65 kg receiving 20 mg oliceridine via PCIA, the oliceridine dosage was 20 mg/65 kg = 0.31 mg/kg). The oliceridine dose for the subsequent patient was reduced by 0.03 mg/kg based on the 0.31 mg/kg dose, with a dose ratio of 1:1.1 between consecutive patients[1]. This dose reduction process continued until the VAS score exceeded 4 at any one of the four predefined time points; this threshold dose was then identified as the minimum effective dose of oliceridine, which served as the baseline PCIA dose for all subsequent patients. If two or more of the four postoperative time points yielded a VAS score >4, the oliceridine dose was increased by 0.03 mg/kg relative to the minimum effective dose determined in the prior patient. Dose escalation was repeated until only one of the four time points presented a VAS score >4.;iliac fascia block with opioiid:For the control group, ultrasound‐guided fascia iliaca compartment block (FICB) with 20 mL of 0. CONDITION: Knee Replacement PRIMARY OUTCOME: Visual analogue scale (VAS) score; SECONDARY OUTCOME: Adverse reactions; INCLUSION CRITERIA: INCLUSION CRITERIA: ASA physical status I–III, and BMI < 30 kg/m^2.