Factors Associated with Postoperative Pain Trajectory, Nausea and Vomiting After Total Knee Arthroplasty: A Retrospective Study.

Objectives: Postoperative pain, nausea and vomiting adversely affect postoperative rehabilitation after total knee arthroplasty (TKA). We aimed to identify factors associated with postoperative pain trajectory and postoperative nausea and vomiting (PONV) and evaluated the effects of different analgesic modalities.

Methods: We retrospectively reviewed patients undergoing unilateral primary TKA from 2017 to 2022. Patients received either general or spinal anesthesia. Patient -controlled analgesia (PCA) included patient-controlled epidural analgesia (PCEA) and intravenous analgesia (PCIA). Outcome variables included maximal pain intensity at certain times (before surgery, and 24h and 48h after surgery); and incidence of PONV. A Generalized estimating equation was used to determine the correlation between PCA usage and longitudinal pain score at 48 hours follow-up after surgery. Multivariable logistic regression analyses were used to evaluate PONV after adjusting for potential confounders.

Results: In total, 2,510 patients were identified. Patients without PCA intervention and with higher BMI reported greater acute postoperative pain. Furthermore, women and lower BMI were associated with higher rates of PONV. After adjusting for confounding factors, the PCEA group had a lower pain score than both the no PCA group (β estimate =-0.443, 95% CI= (-0.561 to -0.324), P<0.001) and the PCIA group (mean difference=-0.227, 95% CI = (-0.328 to -0.126), P <0.001).

Conclusion: General anesthesia and PCA had no effect on the PONV incidence following TKA. Greater BMI correlated with higher pain scores but a lower likelihood of PONV. Epidural PCA provided superior acute postoperative analgesia without increasing the incidence of PONV.