Evaluation of Intraoperative Awareness and Its Correlation With Processed EEG Biomarkers During Laparoscopic Surgery

: Intraoperative awareness is a clinically important complication of general anesthesia in which patients may experience consciousness and subsequently recall events occurring during anesthesia. Intraoperative responsiveness and postoperative explicit recall represent related but distinct aspects of consciousness during general anesthesia.

This prospective observational cohort study will include adult patients undergoing elective laparoscopic abdominal surgery under general anesthesia. Approximately 600 participants will be prospectively enrolled.

Before surgery, participants will undergo baseline assessment using the QoR-15, State-Trait Anxiety Inventory, Mini-Mental State Examination, and Beck Anxiety Inventory.

Processed EEG monitoring will be performed using the Masimo SedLine system. The SedLine system will be applied before induction of general anesthesia and maintained throughout the anesthetic period until extubation. PSI values will be recorded at 5-minute intervals from the beginning of surgery until extubation.

The isolated forearm technique will be used to assess intraoperative responsiveness. The first four IFT assessments will be performed at predefined stages during induction and surgery. A fifth IFT assessment will be performed when the clinical course or monitoring suggests possible awakening, including a PSI value above 50 and/or hemodynamic findings such as tachycardia or hypertension. During the IFT, patients will be instructed to respond to a predefined verbal command, and the presence or absence of a response will be recorded.

PSI values corresponding to IFT assessments will be evaluated. Particular attention will be given to increases in PSI associated with positive IFT responses. A positive IFT response together with an increase in PSI will be considered evidence of intraoperative responsiveness and possible intraoperative awareness rather than definitive proof of explicit postoperative awareness.

At the 24th postoperative hour, patients will undergo QoR-15 assessment and structured questioning regarding possible intraoperative awareness and recall. At the second postoperative week, QoR-15 and Beck Anxiety Inventory assessments will be repeated, and dream recall and possible intraoperative awareness will be assessed.

The study will investigate the relationship between processed EEG-derived PSI values, intraoperative responsiveness detected by the isolated forearm technique, and postoperative reports suggestive of awareness. It will also evaluate associations between possible intraoperative awareness and postoperative quality of recovery, anxiety, and dream recall.

Inclusion criteria

• Age ≥18 years
• Elective laparoscopic abdominal surgery planned
• General anesthesia planned
• Ability to communicate adequately
• Adequate cognitive capacity to understand and respond to study procedures
• ASA physical status I-III

Exclusion criteria

• Previous cerebrovascular disease
• Psychiatric disorders
• Cognitive dysfunction
• ASA physical status >III
• High frailty
• Body mass index >30 kg/m²
• Pregnancy
• Age <18 years