Advanced age is a consistent risk factor for the incidence of postoperative cognitive decline, which is associated with longer hospital stays, decreased quality of life, and increased mortality. Anaesthetic drugs can also affect postoperative cognition, as their residual effects can alter central nervous system activity. Desflurane and sevoflurane are widely used volatile anesthetics. Choice anesthetics may influence the occurrence of postoperative delirium. However, evidence in this aspect is conflicting.

With increasing life expectancy, more and more patients aged 65 or older will receive general anesthesia. Rapid recovery from anesthesia may reduce the incidence of many postoperative complications, such as postoperative delirium and cognitive dysfunction. Using inhalational anesthetics is the mainstay of general anesthesia. Since they pass readily into the brain, anesthetics are usually recognized as the important cause of postoperative cognitive dysfunction. Studies have shown that inhalation anesthesia may increase the risk of postoperative delirium in elderly patients compared to propofol, but such studies mostly focus on isoflurane and sevoflurane. Concentrations isoflurane caused aggregation of amyloid peptides in cell cultures, indicating that they brought cytotoxicity to the brain; sevoflurane also showed the same cytotoxic effect. However, some studies showed that inhalational anesthetics had a protective effect on postoperative cognitive function. Desflurane is currently known to be the least biotransformation inhaled anesthetic, whose blood-gas partition coefficient is only 0.42. Desflurane is increasingly used in elderly patients in clinical practice. However, it is not clear whether general anesthesia maintained mainly by desflurane reduces postoperative delirium and early cognitive dysfunction compared with sevoflurane-based general anesthesia

Inclusion Criteria:

1. Age ≥ 65 years and < 90 years;
2. Scheduled to undergo non-cardiac or non-neurosurgery with an expected duration of 2 hours or more, under general anesthesia;
3. Agree to participate, and give signed written informed consent.

Exclusion Criteria:

1. Preoperative history of schizophrenia, epilepsy, parkinsonism or any diseases of central nervous system;
2. Inability to communicate in the preoperative period (coma, dementia, language barrier, impaired hearing or vision);
3. Severe diseases in cardiovascular, respiratory, liver, kidney, or preoperative American Society of Anesthesiologists physical status classification ≥ IV;
4. Alcoholism and drug dependence;
5. Other reasons that are considered unsuitable for participation by the responsible surgeons or investigators (reasons must be recorded in the case report form).