The research group cannot found time to do the project.

Patients with major orthopedic surgery will be recruited. Participants will be monitored for delirium after surgery. Participants' blood will be harvested for the determination of haptoglobin types, levels of oxidative stress and inflammation. Investigators will then analyze the data to see if haptoglobin 2-2 type is associated with an increased postoperative delirium, inflammation and oxidative stress.

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

Patients who meet the inclusive criteria will be screened as possible candidates.

No plan to share individual participant data with other researchers