This observational study aims to learn about the effects of diabetes mellitus in intraoperative electroencephalography (EEG) of elderly patients receiving general anesthesia. The main question it seeks to answer is:

Is there a relation between preoperative diabetes, intraoperative electroencephalogram suppression ratio, and postoperative delirium?

Participants aged over 65, receiving general anesthesia as part of their anesthesia plan for surgery of any kind, will be monitored with EEG and cerebral oximetry intraoperatively to record burst suppressions and questioned for delirium for 48 hours postoperatively.

3 different patient groups will be observed: those who are diagnosed with diabetes and use oral antidiabetics, those who receive insulin therapy with a diagnosis of diabetes, and patients whose preoperative fasting glucose values are confirmed to be normal without a diagnosis of diabetes.

Patients over 65 who are scheduled for any surgery requiring general anesthesia for at least 30 minutes will be evaluated to detect their basal cognition status with a mini-cognition test and a preoperative anesthesia examination. In addition to routine monitoring, this patient group will also be monitored with electroencephalogram and cerebral oximetry.

Anesthesia induction and maintenance for each patient are applied according to the values here. In the maintenance of anesthesia, sevoflurane will be regulated according to 0.7-1 MAC (adjusted for age), and remifentanil infusion will be regulated according to PSI. Postoperative analgesia will be achieved with tramadol 1 mg/kg and Parol 10 mg/kg (IV) with a target pain score below 4. Each patient will be evaluated with a NUDESC score as a delirium score in the postoperative PACU and during 48 hours in the ward. Values such as suppression time and ratio, the subject of study in EEG recordings during anesthesia, can only be seen by transferring them to the computer with a transfer cable, so the evaluations will be blind. All data transfers will be done after the 48th hour.

Inclusion Criteria:

• Patients over the age of 65 undergoing ASA I-IV receiving general anaesthesia
• All elective surgery patients who are not laparoscopic and last longer than 30 minutes

Exclusion Criteria:

• 1) American Society of Anesthesiologists (ASA) grade V or VI
• Whether the surgery is cranial or laparoscopic
• Preoperative neuropsychiatric (dementia, epilepsy, etc.) disease or drug use
• Previous cranial surgery or known vertebrobasilar insufficiency, carotid stenosis
• Those with a pain score above 4 in the postoperative evaluation unit (PACU)
• Patients with a 15% decrease in cerebral oxygenation from onset in oximetry monitoring during follow-up
• Patients with bleeding greater than 20% of total body volume during follow-up
• Patients with a decrease of more than 20% from their baseline systolic value (based on follow-up in the service) during follow-up
• Those with hypercarbia or hypocarbia due to intraoperative ventilation insufficiency
• Patients whose PSI value is reduced to a depth of 25, which is sufficient for anaesthesia, with anaesthetic drugs administered during anaesthesia induction or maintenance
• Presence of preoperative cognitive dysfunction
• Patients requiring postoperative intubation and intensive care follow-up

Elderly patients receiving general anesthesia