This proof-of-concept study shows promising results regarding the analgesic efficacy of adductor-canal-blockade in post-operative pain treatment after TKA, with a significant reduction in pain during flexion of the knee in the early post-operative period compared with placebo. However, the study was not sufficiently powered to permit final conclusions.
SummaryWe performed a randomised, blinded, controlled study with adult patients scheduled for primary total knee arthroplasty under spinal anaesthesia. The aim was to investigate the analgesic effects of adductor canal block using catheter‐based repeated boluses, either through a new suture‐method catheter or a standard perineural catheter, compared with a single‐injection technique. All patients received an adductor canal block after surgery with an initial bolus of 20 ml ropivacaine 0.75%, followed by 20 ml of ropivacaine 0.2% every 8 h in the standard and suture‐method catheter groups, and sham boluses for the single‐injection group. The primary outcome measure was total opioid consumption (intravenous morphine equivalents) from the end of surgery until 12:00 on postoperative day 2. Secondary outcomes were pain, muscle strength and ambulation. We randomly assigned (1:1:1) and analysed 153 patients. Total opioid consumption was median (IQR [range]) 24 (11–37 [0–148]) mg in the suture‐method group, 38 (17–51 [0–123]) mg in the standard catheter group and 37 (14–57 [0–158]) mg in the single‐injection group (p = 0.049). Differences were not statistically significant after Bonferroni correction (α = 0.05/3). There were no differences between groups on postoperative day 1. On postoperative day 2, there were no differences between catheter groups, but muscle strength and ambulation were improved compared with the single‐injection group. We conclude that providing repeated boluses via a catheter did not decrease opioid consumption or pain compared with a single injection, but improved muscle strength and ambulation on postoperative day 2. The two types of catheters were similar.
For ACB, there is a positive correlation between local anesthetic volume and effect on the vastus medialis muscle. Despite the rather large differences in EMG recordings, there were no statistically significant differences in quadriceps femoris muscle strength. Subsequent clinical studies comparing different volumes in a surgical setting, powered to show differences not only in analgesic efficacy, but also in adverse events, are required.
Changing the mode of administration for an ACB from continuous infusion to repeated intermittent boluses did not decrease opioid consumption, pain, nor mobility.
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