Perioperative neurocognitive impairment (PND) mainly includes acute postoperative delirium (POD) and persistent postoperative cognitive impairment (POCD), which are common postoperative complications in elderly patients. Perioperative neurocognitive impairment (PND) is attracting increasing attention, but its exact mechanism is still unclear. The diagnosis of PND lacks the gold standard, so it is difficult to determine the incidence rate. At present, the diagnosis is mainly conducted through the scale. Therefore, this study aims to explore the correlation between peripheral blood biomarkers and PND in elderly frail patients undergoing gastrointestinal surgery.

Inclusion Criteria:

• Age ≥ 65 years old
• American Society of Anesthesiologists (ASA) classification: grades I-IV
• Hospitalization time ≥ 3 days

Exclusion Criteria:

• The revised version of the Cognitive Function Telephone Questionnaire (TICS-M) was used before surgery to determine cognitive impairment (TICS-M score ≤ 27 points)
• Refuse to participate
• Emergency surgical patients
• Central nervous system diseases (dementia, depression, etc.)
• Severe renal insufficiency (requiring dialysis)
• Long term use of psychotropic drugs (such as clozapine, risperidone, olanzapine, haloperidol, chlorpromazine, etc.)
• History of alcohol abuse or use of acetylcholine drugs
• The same patient can only be included once, regardless of whether the reason for the second surgery is related to the first cause

Elderly patients undergoing gastrointestinal surgery under general anesthesia.