Effects of Local Anaesthetic Infusion Rates on Nerve Block Duration

This trial is a part of the project: 'A novel technique for reliable, precise and safe postoperative pain management' (project no. 65-2014-3). The purpose of the trial is to investigate the effects of changing peri-neural infusion rates of ropivacaine 0.2% on the duration of nerve block. Intervention: Two intervention-days. Each day a peri-neural infusion of a fixed volume of ropivacaine 0.2% is to be infused in one of five infusion rates, using a peri-neural catheter. Intervention day 1: Focus on the common peroneal nerve. Intervention day 2: Focus on the sciatic nerve.