Continuous Versus Automated Bolus Infusion in Sciatic Nerve Catheters

This study is developed to determine if the local anaesthetic dose can be reduced by the use of intermittent bolus technique compared to continuous infusion when the nerve catheter is placed underneath the paraneurium by ultrasound guidance in the popliteal fossa. Our primary outcome is local anesthetic use the first 48 hours after connecting the peripheral nerve catheter. Our hypothesis is that with an intermittent bolus less local anaesthetic is necessary the first postoperative 48 hours after surgery for adequate postoperative analgesia. As secondary outcomes the investigators study pain scores, motor block, sensory block, feeling of numbness, patient satisfaction, sleep quality and rescue analgesia during the nerve block and afterwards.