Ultrasound-guided continuous femoral nerve block: a randomized trial on the influence of femoral nerve catheter orifice configuration (six-hole versus end-hole) on post-operative analgesia after total knee arthroplasty

BACKGROUND: Multiorifice catheters have been shown to provide superior analgesia and significantly reduce local anesthetic consumption compared with end-hole catheters in epidural studies. This prospective, blinded, randomized study tested the hypothesis that, in continuous femoral nerve block (CFNB) under ultrasound guidance, multiorifice catheter would reduce local anesthetic consumption at 24 h compared with end-hole catheter. METHODS: Eighty adult patients (aged ≥18 years) scheduled to undergo primary total knee arthroplasty under a combination of CFNB, sciatic nerve block and general anesthesia were randomized to CFNB using either a 3-pair micro-hole (Contiplex, BRAUN®, 20G - 400 mm) or an end-hole (Silverstim VYGON®, 20G - 500 mm) catheter. Once the femoral catheter was sited, a bolus of 20 mL lidocaine 1% was injected. An electronic pump then delivered an automated 5 mL bolus of ropivacaine 0.2% hourly, with 10 mL self-administered patient controlled analgesia boluses. RESULTS: There was no inter-group difference in either median number of ropivacaine boluses on demand during the first 24 h (4(2–7) vs. 4(2–8) in six-hole and end-hole groups, respectively; P = 0.832) or median ropivacaine consumption at 48 h (365(295–418) vs. 387(323–466); P = 0.452). No significant differences were recorded between the groups at 24 h regarding median average verbal rate pain scale (2(0–3) vs. 2(0–4); P = 0.486) or morphine consumption (0(0–20) vs. 0(0–20); P = 0.749). Quadriceps muscle strength declined to 7% (0–20) and 10% (0–28) in the six-hole and end-hole groups, respectively, at 24 h after surgery (P = 0.733). CONCLUSIONS: In this superiority trial, catheter orifice configuration did not influence the effectiveness of CFNB in this setting: quality of analgesia was similar, with no reduction in either local anesthetic or morphine consumption, and equivalent postoperative quadriceps weakness. TRIAL REGISTRATION: Retrospectively registered at (NCT03376178). Date: 21 November 2017.