Earlier Is Better? Timing Of Adductor Canal Block For Arthroscopic Knee Surgery Under General Anesthesia: A Retrospective Cohort Study

The adductor canal block (ACB) is effective for treating postoperative pain during arthroscopic knee surgery, but its impact on anesthesia course and the optimal administration timing are unknown. This retrospective study addressed these questions. The aim of this study was to compare the effects of preoperative ACB and postoperative ACB on anesthesia course and postoperative recovery. We allocated 215 adult patients who underwent arthroscopic knee surgery under sevoflurane anesthesia between January 2019 and December 2019 to three groups. Group A received general anesthesia without ACB, Group B received ACB before general anesthesia induction, and Group C received ACB in the post-anesthesia recovery unit (PACU). Group B consumed significantly less sevoflurane (0.19 mL/kg/h) and milligram morphine equivalents (0.08 MME) intraoperatively than Groups A (0.22 mL/kg/h; 0.10 MME, respectively) and C (0.22 mL/kg/h; 0.09 MME, respectively). Groups B and C had lower visual analogue scale (VAS) scores upon PACU discharge than Group A. Dynamic, but not at-rest VAS scores, were significantly higher in Group A. Opioid consumption was similar in the ward, but Group A requested more intravenous parecoxib for pain relief. Length of hospital stay was similar. Thus, preoperative ACB reduced the amount of volatile anesthetic required and maintained stable hemodynamics intraoperatively. Preoperative or postoperative ACB improved postoperative pain control. Consequently, preoperative ACB is optimal for intraoperative stress suppression and postoperative pain control.