Postoperative analgesia and early functional recovery after day-case anterior cruciate ligament reconstruction: A randomized trial on local anesthetic delivery methods for continuous infusion adductor canal block

BACKGROUND: This study assessed the effects of different local anesthetic delivery techniques for continuous adductor canal block, after arthroscopic day-case anterior cruciate ligament reconstruction (ACLR). METHODS: We enrolled 80 patients to randomly receive a ropivacaine 0.2% infusion 6 mL per hour through an adductor canal catheter by an electronic pump as follow: intermittent automatic bolus (intermittent group, N.=40) versus continuous infusion (continuous group, N.=40). Patient controlled bolus was 4 mL, lock out 20 minutes. Primary endpoint was postoperative pain by a numerical rating scale (NRS), secondary endpoints were rescue local anesthetic dose, opioid consumption, and physical performance at 72 h. A P<0.05 was considered significant. RESULTS: No difference was found between the groups in NRS, opioid consumption, and physical performance at 72 h. The intermittent group required significantly less local anesthetic than continuous group throughout the postoperative period; the median [IQR (range)] at 24 h was 149 [140-164 (140-227)] mL in the intermittent group versus 165 [147-210 (140-280)] mL in the continuous group (P=0.004). At 48 h it was 295 [284-310 (280-367)] mL in the intermittent group versus 308 [296-367 (284-500)] mL in the continuous group (P=0.002), while at 72 h it was 432 [426-450 (320-528)] mL in the intermittent group and 452 [436-487 (412-671)] mL in the continuous group respectively (P<0.001). CONCLUSIONS: Intermittent boluses did not provide superior analgesia over continuous infusion for adductor canal block after outpatient ACLR, but significantly decreased the local anesthetic consumption. Both techniques are suitable for the early functional recovery.