This study intends to verify and explore the correlation of neuroinflammation biomarkers in cerebrospinal fluid and plasma of elderly patients undergoing hip replacement with postoperative delirium, so as to achieve a new method to predict whether patients will develop postoperative delirium and improve the prognosis of elderly patients with postoperative delirium. Reduce the probability of postoperative complications, improve the long-term survival rate of patients after surgery.

Inclusion Criteria:

1. age≥65
2. Patients undergoing hip replacement under spinal anesthesia
3. ASA grade I~III;
4. Voluntarily participate in this study, and informed consent was signed by the patients themselves and their families

Exclusion Criteria:

1. Patients with multiple fractures and trauma
2. Patients with preoperative cognitive dysfunction determined by MMSE scale;
3. Severe impairment of hearing, visual and language system functions;
4. Not suitable for or unwilling to undergo subarachnoid anesthesia
5. Patients who refuse to participate or cannot cooperate.

Elderly patients undergoing hip replacement surgery in Henan Provincial People's Hospital were selected during the trial