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 24h compared with end-hole catheter.

Eighty adult patients (aged ≥18 years) scheduled to undergo primary total knee arthroplasty under a combination of continuous femoral nerve block (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.

Inclusion Criteria:

• every patient accepting a conitnuous femoral nerve catheter

Exclusion Criteria:

• pregnancy,
• any contraindication to peripheral nerve blockade,
• pre-existing peripheral nerve neuropathy,
• allergy to LA (study medications),
• ASA score ≥4,
• neurologic or neuromuscular disease,
• psychiatric disease,
• renal failure,
• hepatic failure,
• chronic opioid therapy,
• NSAID contraindication,
• inability to use a patient controlled analgesia (PCA) device, g
• enu valgum,
• infection at the injection site or
• withdrawal of consent.

All investigators, patients, and other clinical staff were blinded to the treatment group. The investigator in charge of the patient was unaware of patient allocation. He did not perform the block or open the sealed and opaque envelope, but followed the patient in the ward. An opaque skin dressing was used in order to blind the type of catheter used. End-hole catheter Vygon is white and stiff whereas six-hole catheter contiplex is yellow and flexible.