Fifty adult patients (aged 20-60 years; ASA I-III) scheduled for elective laparoscopic abdominal surgery (e.g., cholecystectomy, appendectomy, hernia repair) under general anesthe-sia were enrolled. All patients underwent standardized anesthetic management. Following preoxygenation with 100% oxygen for 2 minutes, anesthesia induction consisted of intravenous thiopental sodium (5-7 mg·kg-¹), fentanyl (1 µg·kg-¹), rocuronium (0.6 mg·kg-¹), and lidocaine (1 mg·kg-¹). Tracheal intubation was performed by an experienced anesthesiologist, with laryngoscopy duration recorded. Anesthesia was maintained with 1 minimum alveolar concentration (MAC) sevoflurane in 50% O2/air mixture, using volume-controlled ventilation (tidal volume 6-8 mL·kg-¹, PEEP 5 cmHO2, respiratory rate adjusted to maintain end-tidal CO2 [EtCO2] 33-40 mmHg). Hemodynamic variables, and peak inspiratory airway pressure (Ppeak) were continuously recorded.

All parameters (ONSD, rSO2, IAP, EtCO2, Ppeak, SBP, DBP, MAP, HR) were recorded at:T0: Pre-induction baseline,T1: 5 min after induction,T2: 5 min after COpneumoperitoneum,T3: 30 min after pneumoperitoneum,T4: 5 min post-desufflation. ONSD was measured using a high-frequency (18 MHz) linear ultrasound probe (Mylab 5, Esaote, Genoa, Italy). The ONSD was defined as the distance between the outer edges of the optic nerve sheath 3 mm posterior to the optic disc. rSO2 was measured continuously using NIRS (INVOS 4100) with bilateral frontal sensors. MMSE, administered in a face-to-face format by a trained researcher on the day before surgery (baseline) and 24 hours postoperatively. A decline of ≥2 points in the postoperative score compared to baseline was considered indicative of postoperative cognitive dysfunction (POCD).

ONSD was measured by a single trained anesthesiologist using a high-frequency (18 MHz) linear ultrasound probe (Mylab 5, Esaote, Genoa, Italy). With patients in the supine position and eyelids closed, the probe was gently placed on the upper eyelid in horizontal and vertical planes without exerting pressure. The ONSD was defined as the distance between the outer edges of the optic nerve sheath 3 mm posterior to the optic disc.

Cognitive performance was evaluated using the Mini-Mental State Examination (MMSE), administered in a face-to-face format by a trained researcher on the day before surgery (baseline) and 24 hours postoperatively.The Mini Mental State Examination (MMSE) test consists of 11 questions and is evaluated from a minimum score of 0 to a maximum of 30, below 24 point is considered worse outcome, while a decline of ≥2 points in the postoperative score compared to baseline was considered indicative of postoperative cognitive dysfunction (POCD), consistent with prior studies.