Comparison of Oral Patient-Controlled Analgesia versus Intravenous Nurse-Controlled Analgesia After Unilateral Total Knee Arthroplasty: A Randomized Non-Inferiority Trial

Abstract

Background: Postoperative pain control after total knee arthroplasty may remain inadequate despite the use of multimodal analgesia. Oral patient-controlled analgesia (PCA) may provide more timely access to rescue medication; however, evidence comparing this approach with intravenous analgesia administered by nurses remains limited.
Objective: To determine whether oral PCA is non-inferior to intravenous nurse-controlled analgesia (NCA) for pain control after unilateral total knee arthroplasty (TKA).
Materials and methods: This randomized controlled non-inferiority trial included patients aged 50–70 years undergoing unilateral TKA. When rescue analgesia was required, participants were randomly assigned to receive either intravenous morphine 3 mg administered by a nurse at a minimum interval of 4 hours or immediate-release oral morphine 10 mg self-administered at a minimum interval of 1 hour. The primary outcome was the mean pain score at rest during 36–48 hours after surgery. The prespecified non-inferiority margin was 1.8 points on a 0–10 numerical rating scale.
Results: Sixty-four patients were randomized, with 32 assigned to each group. One patient in the oral PCA group did not receive the allocated intervention. The per-protocol analysis therefore included 63 patients. The mean resting pain score at 36–48 hours was 3.3±2.0 in the oral PCA group and 3.2±1.7 in the NCA group. The mean difference (NCA minus oral PCA) was 0.0 points (95% confidence interval [CI], −1.0 to 0.9), and the entire CI lay within the prespecified non-inferiority margin. Patients in the oral PCA group received morphine more frequently than those in the NCA group (median, 3 vs. 0 doses; p<0.001) and were more likely to report high or very high satisfaction (90.3% vs. 56.2%; p=0.022). Nausea, vomiting, and dry mouth were more common in the oral PCA group. All adverse effects were mild, and none required withdrawal from the study.
Conclusion: Oral PCA was non-inferior to NCA for controlling resting pain at 36–48 hours after unilateral TKA and was associated with higher patient satisfaction. However, mild adverse effects occurred more frequently with oral PCA. Oral PCA may therefore be considered an alternative analgesic strategy in resource-limited settings for appropriately selected patients.