Efficacy of epinephrine in local infiltration analgesia on pain relief and opioid consumption following total knee arthroplasty: a randomized controlled trial

Local infiltration analgesia (LIA) is one of the effective regimens to reduce pain after total knee arthroplasty (TKA). Epinephrine is a commonly used sympathetic adjunct in LIA. It is expected to enhance the intensity and extend the duration of LIA. The primary aim of the study was to evaluate the efficacy of epinephrine on postoperative pain control after primary TKA. A total of 80 patients who underwent primary TKA were randomized into an epinephrine (EN) and a control (C) group. Postoperative visual analogue pain score (VAPS) and morphine consumption were recorded every 6 hours until 48 hours after operation. The VAPS 6-48 hours were compared using repeated measure statistics. The range of motion (ROM) on discharge and complications were also compared between these 2 groups. The study showed that although VAPS differed statistically between the 2 groups at 12 hours (C higher) and 48 hours (C lower) postoperatively (p = 0.04 and 0.02, respectively), repeated measures analysis revealed that there were no significant differences in 6-48 hours VAPS (p = 0.6). Total morphine consumption in the EN and C groups was 3.4 (SD 3.7) and 4.2 (SD 4.4) mg, respectively (p = 0.4). ROM on discharge was also similar between the groups. No complications were detected in this study. Our study showed that additional epinephrine in LIA had a statistically significant reduction in VAPS at 12 hours and morphine usage during 6-12 hours when compared with the control group. However, the magnitude of difference did not reach minimal clinically importance difference (MCID) value for TKA.