Deep anesthesia reduces postoperative cognitive dysfunction in elderly patients: Postoperative cognitive dysfunction (POCI) refers to the slow recovery of cognitive abilities such as orientation, thinking, memory, attention, and self-awareness that occurs after surgical anesthesia, which can prolong hospitalization and, in severe cases, affect the patient’s quality of life after discharge. PurposeThere is no uniform view on the effect of anesthesia depth on the occurrence of POCD Studies have shown that maintaining an intraoperative BIS value of 30-40 is considered more conducive to the recovery of cognitive function in the early postoperative period. It has also been shown that there is no difference in the incidence of (POCD) at different depths of anesthesia and that old age is an independent risk factor for the occurrence of POCD. In this study, we intend to evaluate the effect of different depths of anesthesia on the occurrence of POCD in elderly patients. Factors such as age, education level, anesthesia method, intraoperative bleeding and rehydration, as well as hypoperfusion of brain tissues due to intraoperative hypotension, stress reaction and surgical trauma were associated with the occurrence of POCD. In this study, the study subjects were all elderly patients aged 65-78 years who underwent radical surgery for gastrointestinal malignant tumors under general anesthesia, and there was no difference in the years of education, intraoperative bleeding, blood transfusion, rehydration, and incidence of hypotension between the 2 groups, so that the influence of these factors could be excluded. MMSE score is a commonly used method to determine postoperative cognitive function, which is simple and easy to use, with high reliability and validity.BIS is a commonly used clinical indicator to monitor the depth of sedation and depth of anesthesia.BIS value of 80-100 is awake state, 60-79 is light anesthesia, 40-59 is clinical anesthesia, and <40 is deep anesthesia. Studies have shown that there is no significant difference in the incidence of POCD in general anesthesia patients when BIS values are maintained at 40-50 versus 50-60. Other studies have shown that intraoperative BIS values of 30-40 are more favorable to the recovery of cognitive function in the early postoperative period. Therefore, BIS values of 30-39 and 50-59 were chosen for this study. General anesthetics can inhibit the function of the central cholinergic system and can be maintained until some time after anesthesia, which leads to the occurrence of POCD. Surgical stimuli leading to stress response can impair the memory and learning ability in the hippocampus of elderly patients, which in turn leads to POCD. Studies have shown that deeper anesthesia can suppress the levels of cortisol, epinephrine, norepinephrine, etc., in the blood and reduce the body's stress response, which in turn reduces the occurrence of POCD in elderly patients. Other studies have shown that deep anesthesia can significantly reduce the rate of cerebral oxygen metabolism and decrease the occurrence of POCD in elderly patients. In conclusion, deep anesthesia (maintaining BIS value of 30-39) can reduce the occurrence of POCD in elderly patients undergoing radical surgery for gastrointestinal tumors.