During and after the surgery, patients undergoing surgery most likely need narcotics (opioids) that can cause side effects such as drowsiness and constipation. This can delay your recovery. The investigator would like to determine if the intraoperative use of ketamine and methadone will provide better pain control and reduce the use of narcotic painkiller medications (analgesics) after lumbar surgery as compared to either drug (ketamine or methadone) alone.