 After consenting, patients will be randomized by the pharmacy. In the operating room patients will receive ketamineplacebo 0.5mgkg bolus prior to the surgical incision, followed by ketamineplacebo 0.2mgkg continuous infusion up to 48hours. All the patients will also receive 15mgk IV acetaminophen at the end of the surgery, followed by every 6hr for 48hrs. Rest of the pain regimen will be the usual post-operative pain management for spinal fusion for idiopathic scoliosis, which includes morphine PCA, IV ketorolac from POD 1, and flexaril from POD 1. 