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

BACKGROUND AND OBJECTIVES: Lumbar plexus block (LPB) is an effective perioperative analgesic therapy for patients undergoing total hip arthroplasty (THA). However, the analgesic efficacy of intermittent administration compared with continuous infusion of LPB in patients remains unclear.

METHODS: Forty adult patients who underwent THA were randomly divided into two groups: continuous infusion group (6 mL/hour continuous infusion of levobupivacaine [0.125%] in LPB, n=20) and intermittent infusion group (12 mL of levobupivacaine [0.125%] bolus delivered every 2 hours in LPB, n=20). The primary outcome was the cumulative fentanyl consumption administered for rescue analgesia during the first 48 hours after surgery. Secondary outcomes were the number of demands for rescue analgesia and successfully delivered rescue analgesia; extent of sensory blockade (cold tests); and pain score on the visual analog scale (VAS) at rest and during mobilization during the first 48 hours after surgery.

RESULTS: Both the cumulative fentanyl consumption administered for rescue analgesia (mean [SD]: 81.5 [58.5] μg vs 438 [101.2] μg among the intermittent infusion and the continuous infusion groups, respectively) and the number of demanded and delivered fentanyl boluses for rescue analgesia were lower in intermittent infusion group than in continuous infusion (p<0.001 for both). The extent of sensory blockade remained constant in intermittent infusion group, but gradually narrowed in continuous infusion. VAS was lower in intermittent infusion group than in continuous infusion, except at 1 and 12 hours postoperatively (p<0.05).

CONCLUSIONS: Greater analgesic effect was achieved using the intermittent mode than the continuous mode of LPB administration.