Post-operative analgesia using intermittent vs. continuous adductor canal block technique: a randomized controlled trial

Background and objectivesIntermittent boluses for neural blockade provide better post-operative analgesia when compared to continuous infusion. However, these techniques of administration have not yet been compared while performing adductor canal block (ACB). We compared intermittent vs. continuous ACB for managing post-operative pain following anterior cruciate ligament (ACL) reconstruction. The primary endpoint was total morphine consumption for 24h post-operatively in both the groups. Secondary outcomes included evaluation of pain scores and opioid-related side effects. MethodsAfter ethics board approval, subjects presenting for ACL reconstruction were randomized to receive either continuous ACB (n=25) with 0.5% ropivacaine infusing at 2.5ml/h or intermittent boluses (n=25) of 15ml of 0.5% ropivacaine every 6h. Total morphine consumption 24h following surgery was recorded in each group. ResultsFifty subjects completed this study. The mean 24-h total morphine consumption in the intermittent group, [11.36 (6.82) mg], was significantly reduced compared with the continuous group, [23.40 (10.45) mg] (P<0.001). The mean visual analogue scale (VAS) pain score at rest and on knee flexion was significantly reduced in the intermittent group at 4, 6, 8, and 12h compared with the continuous group. ConclusionIntermittent ACB allowed significantly reduced consumption of morphine for 24h in the post-operative period compared with continuous ACB when identical doses of ropivacaine were used in each group.