Continuous administration of local anesthetic for pain after amputation above knee

INTERVENTION: Continuous peripheral infusion of local anesthetic ropivacaine for 72 hours through two catheters, placed in the sciathic nerve sheath and under the amputation wound. The randomisation was done with computer‐generated randomisation list on random.org, in blocks of ten patients. It was done by a person who is not working with the study otherwise. The follow‐up is done by a study nurse who contacts the patients by a telephone call on 1, 3 and 12 months after the operation. CONDITION: Pain after amputation above knee ; Signs and Symptoms PRIMARY OUTCOME: Pain on the amputated limb 1‐5 days after the operation assessed on VRS 0‐4. SECONDARY OUTCOME: 1. Pain on the amputated limb 1,3 and 12 months after the operation and amputation phantom limb pain 1‐5 days after the operation and 1, 3 and 12 months after the operation on VRS 0‐4; 2. The consumption of opioid 1‐5 days after the operation ; 3. Adverse events INCLUSION CRITERIA: 1. Patients presenting for above knee amputation for atherosclerosis obliterans willing to participate 2. Able to give informed consent 3. Able to assess pain using a verbal rating scale 4. Assesssed to be medically stable so that life expectancy exceeds 2 weeks as assessed by recruiting anesthesiologist