The goal of this [type of study: observational study ] is to [compare Energy differences in various bands of intraoperative electroencephalogram in elderly patients with postoperative delirium and non delirium.] in [describe participant population selected 69 patients who underwent laparoscopic radical surgery for colorectal cancer on a selective basis]. The main question[s] it aims to answer are:

• [Is there any difference in the spectral range of EEG between POD patients and non POD patients] Participants will [Cognitive.•Postoperative delirium.•Preoperative weakness.]

The goal of this [type of study: observational study ] is to [compare Correlation between EEG data and postoperative delirium in elderly patients undergoing colorectal cancer radical surgery under preoperative frailty monitoring.] in [describe participant population selected 69 patients who underwent laparoscopic radical surgery for colorectal cancer on a selective basis]. The main question[s] it aims to answer are:

• [Is there any difference in the spectral range of EEG between POD patients and non POD patients] Participants will [Sedline EEG monitoring electrodes were placed 1cm above the eyebrows on both sides of the patient and at the temples on both sides, and were continuously monitored from the start of anesthesia in the operating room until the end of the surgery.Pay close attention to the vital signs and wait for the patient to fully recover and the vital signs to basically return to the preoperative level before returning to the ward.•Assessment of cognitive function using the Mini Mental State Scale (MMSE) 1 day before surgery and 7 days after surgery.•Preoperative assessment of frailty using the frailty screening scale.•Assess delirium using the ICU Patient Ambiguity Assessment Form (CAM-ICU) 1 day, 2 days, 3 days, and 7 days after surgery.].

Inclusion Criteria:

• ASA I-III
• The preoperative Frailty Scale (FRAIL) assessed frailty
• The patient or his/her family is informed about the study and signs an informed consent form

Exclusion Criteria:

• Serious insufficiency of heart, liver, kidney and other functions
• Those with a history of psychiatric or neurological illness, long-term use of psychotropic drug
• History of cerebrovascular disease, brain trauma, or surgery
• The patient was allergic to coupler or unable to place electrodes on the head
• The patient was unable to complete the scale assessment as required.Patients with severe attention to hearing impairment were unable to complete the interview
• The patient was diagnosed with delirium before surgery

Patients undergoing laparoscopic radical surgery for colorectal cancer on a scheduled basis.Age ≥ 65 years old, regardless of gender; ASA grading I to III; The preoperative frailty scale (FRAIL) was evaluated as frailty; The patient or their family members voluntarily sign an informed consent form.