A 4884 patient, multicentre, double blind placebo-controlled, parallel group randomized trial of the effect of perioperative intravenous ketamine on the incidence and severity of chonich post-surgical pain. Our primary hypothesis is that an intravenous (IV) ketamine infusion (commenced with a loading dose prior to surgical incision and run for 72 hours postoperatively in patients undergoin anaesthesia for abdominal, thoracic or major orthopaedic surgery, will reduce the incidence of chronic postsurgical wound pain at 12 months after surgery, compared with placebo. We will also measure the treatment effects on chronic pain severity and character, associated psychological and quality of indices, acute pain and analgesic requirements, quality of postanaesthetic recovery and cognitive function, hospital stay and longer term healthcare utilization costs.