Comparison of a Single Shot Femoral Nerve Block to Femoral Nerve Block Shot Plus Continuous Femoral Nerve Catheter for Total Knee Replacement Surgery; a Randomized, Blinded Controlled Trial.

The study will be a randomized controlled blinded study with a sham control arm. The patients will be randomized to either a single shot FNB with placement of a catheter on the skin (sham control) or a conventional CFNC with catheter.

The group with SSFNB will receive a femoral nerve block before the surgery in the pre-operative area guided by a nerve stimulator and ultrasound. A bolus of 0.5 % ropivacaine will be injected around the femoral nerve. A catheter would be placed on the skin, without penetration, with occlusive dressing applied over the site. A standard size saline bag will be placed on the pump but will not be turned on. The tubing will be opaque and a bag will be placed over the pump to blind the patient to the medication, or lack of medication, being administered. The patient, nursing staff and physical therapists will be blinded to the presence of a sham catheter. The infusion will be labelled 'Study Drug R' or 'Study Drug N' in the electronic medicine prescription.

The group randomized with active drug by CFNB would have a continuous femoral catheter placed using nerve stimulator and ultrasound. Catheter will be bolused with 0.5 % ropivacaine around the femoral nerve and occlusive dressing applied over the catheter.

After placement of the femoral nerve block patients will be transported to the operating room and spinal anesthesia with bupivacaine and fentanyl will be performed. Intra-operative sedation of propofol infusion will be titrated to the discretion of the anaesthesia team. Patients will receive scheduled as well as rescue analgesia as per clinical pathway protocol.

Patients with CFNB will receive ropivacaine 0.2% infusion (the infusion rate will be dependent on the clinical judgement of the anaesthesiologist) in the post anaesthesia care unit (PACU) after the spinal anaesthesia has worn off. The infusion will be continued for the duration of the catheter, 4am POD one. Patients with SSFNB will not receive any infusion through the sham catheter.