Intraoperative timing of local infiltration analgesia impacts perioperative pain management in primary total knee arthroplasty: a single-blind randomized controlled clinical trial.

Abstract

Background: Local infiltration analgesia (LIA) for primary total knee arthroplasty (TKA) is a standard procedure that is considered safe and simple. However, there is still ambiguity in the execution, technique and timing. Starting LIA at the earliest possible time could spare intraoperative opioids and prevent postoperative sensitization.

Methods: Seventy patients for elective primary TKA, randomly allocated to both study groups (LIA-early N.=35, LIA-late N.=35) were included in this randomized controlled trial comparing early LIA (administered in three steps at the start and during knee joint preparation) and late LIA (administered after femur and tibia resection and during withdrawal). The primary endpoint was intraoperative opioid consumption as measured in morphine equivalent dose (MED). Secondary endpoints included total perioperative opioid consumption until discharge, pain intensity, mobility, and length of hospital stay (LOS).

Results: Intraoperative opioid consumption showed no significant difference (LIA-early: median [IQR], 2.85 [2.04-3.37] vs. LIA-late: 3.1 [2.64-3.67] mg/kg; P=0.275). On POD 1-3 cumulative postoperative MEDs (LIA-early: 0.4 [0.1-0.075] mg/kg vs. LIA-late: 1.37 [0.91-1.91] mg/kg; P=0.001, r=0.58), pain scores (P<0.001), LOS (P=0.001, r=0.61), and time to achieve 90° flexion (P=0.001, r=0.71) differed significantly favoring early LIA.

Conclusions: Early compared to late LIA did not reveal significant differences in intraoperative opioid-sparing effects, but significantly reduced postoperative opioid consumption, pain scores, and time of recovery. The mechanisms behind these findings are unclear.