A Study of Huperzine A Injection in Reducing Postoperative Delirium in Elderly Patients Undergoing Non-cardiac Surgery

Inclusion Criteria: * ≥ 75 years old. * Comply with the indication of non-cardiac surgery under general anesthesia. * Anesthesia grade of American Society of Anesthesiologist (ASA) as III\~IV grade. * The estimated operation time ≥ 2 hours. * Voluntarily sign the informed consent form. Exclusion Criteria: * Patients with impaired renal function (Cr is 1.5 times higher than the upper limit of the normal value of the central laboratory) or abnormal liver function (Alanine aminotransferase(ALT) and Aspartate aminotransferase(AST) are 2 times higher than the upper limit of the normal value of the central laboratory). * Patients who are positive for infectious diseases. * Patients accompanied with central nervous system injury. * Patients with previous history of delirium and epilepsy, long-term use of psychoactive drugs or preoperative assessment of delirium. * Patients who involved diseases with drug taboos, bronchial asthma, mechanical intestinal obstruction and urinary tract obstruction, or serious systemic diseases, especially circulatory diseases: such as myocardial infarction, heart failure, angina pectoris, history of sinus bradycardia. * Patients who are known to be allergic to narcotic drugs or Huperzine A Injection, or must use drugs that are not compatible with Huperzine An Injection. * patients who participated in other clinical trials within 3 months before this study, for any reason, who could not tolerate the test or cooperate with the examination, or who has any aphasia, audio-visual dysfunction, etc. * the investigators think that the patients is not suitable to participate in this study.