This case-control study is planned to recruit patients who meet the enrollment conditions, receive cardiac surgery (cardiac valve surgery or coronary artery bypass surgery) and cardiopulmonary bypass, and sign the informed consent form in the second ward of adult cardiac surgery, Fuwai Hospital. Use RASS, CAM-ICU scales to evaluate postoperative patients and divide them into delirium and non-delirium groups according to whether they had delirium after surgery. There will be 30 patients in each group. Match the two groups in terms of surgical type, duration of cardiopulmonary bypass, gender and age range (± 3 years). Collect and record the preoperative, intraoperative and postoperative data of the enrolled patients, including cardiopulmonary bypass time, ICU stay time, length of mechanical ventilation, hemodynamics and other data. Fecal and/or blood samples are collected from 60 patients before, immediately after and after operation.

The laboratory test and analysis shall be started after the collection of clinical samples. Fecal samples are used for Metagenomics Sequencing and Functional genomics. Blood samples are analyzed by serum metabolomics for changes in intestinal metabolites entering the blood circulation. Simultaneous measurement of IL-6 and TNF in peripheral blood with serum samples- α, IL-1a,IFN-γ and LPS, D-lactic acid and diamine oxidase levels.Use Multi-omics approach to analyze the correlation between intestinal flora diversity, functional gene abundance and blood metabolites, inflammation level and intestinal barrier function, and to find the clinical evidence of the correlation between microbiota-gut-brain axis and the occurrence of POD in patients. Through comprehensive analysis of the research results of this experiment, access to literature, write papers, submit papers and publish relevant papers.

Inclusion Criteria:

• elective cardiac valve surgery or coronary artery bypass grafting
• open heart surgery under hypothermic cardiopulmonary bypass under intravenous and/or inhalation general anesthesia
• No history of delirium attack, no cognitive impairment, normal speech, and certain ability of speaking and reading
• age>18
• Informed consent of patients, voluntary participation (or consent of family members), and signing of informed consent

Exclusion Criteria:

• There are organic brain diseases (preoperative brain CT examination)
• Hearing or visual impairment that may affect delirium assessment
• Suspected or confirmed history of alcohol/drug/drug abuse
• Previous history of mental illness or preoperative use of antipsychotic drugs
• Moderate and severe renal function damage (blood creatinine > 2mg/dL or 177mmol/L) or abnormal liver function (alanine aminotransferase>2 times the upper limit of normal value) or other serious lung diseases
• Hematologic diseases, bone marrow and/or lymphoid diseases, leukopenia
• Use immunosuppressive drugs or autoimmune diseases
• Pregnant
• Accompanied by other diseases that may affect their survival, such as tumor
• HIV

patients who meet the enrollment conditions, receive cardiac surgery (heart valve surgery or coronary artery bypass surgery) and cardiopulmonary bypass (CPB) in the Department of Cardiovascular Surgery, Fuwai Hospital, Chinese Academy of Medical Sciences.