Greater analgesic effect with intermittent compared with continuous mode of lumbar plexus block for total hip arthroplasty: a randomized controlled trial

40 patients scheduled for total hip arthroplasty were randomized to post-operative analgesia with either an intermittent or continuous lumbar plexus block (LPB). The primary outcome of interest was cumulative fentanyl consumption. Secondary outcomes of interest included pain at rest and during movement (measured on a Visual Analog Scale (VAS)), the number of demands for and successfully delivered rescue analgesia, and the number of segments with sensory blockade. Follow up was performed up to 48 hours post-operation. Results revealed significantly lower fentanyl consumption in the intermittent group compared to the continuous group up to 48 hours post-operation. VAS pain scores at rest and during motion were largely in favour of the intermittent group. The number of demands for an successfully delivered rescue analgesics were significantly lower in the intermittent group compared to the continuous group. Sensory blockade declined significantly from 2 hours post-operation in the continuous group.