Association of Haptoglobin 2-2 With Postoperative Delirium

Inclusion Criteria: * American Society of Anesthesiologists physical status I to III class for major orthopedic surgery (hip or knee replacement or spinal surgery) * No psychological and psychiatric history and presentation before surgery * No major organ dysfunction or failure Exclusion Criteria: * Anemia (hemoglobin \< 100 g/l) preoperatively. * Requires \> 4 units of allogeneic red blood cell transfusion during the surgery * Using steroids or anti-psychological and anti-psychiatric drugs. A small dose of steroid for postoperative anti-nausea/vomiting is allowed and will not be considered as a indication for exclusion. * Can not cooperate with the study * History of bleeding * BMI \< 18 or \> 30 * History of hemoglobin metabolism disorder