The Effects of Positive End-expiratory Pressure (PEEP) on Optic Nerve Sheath Diameter in Laparoscopic Cholecystectomy

The Effects of Positive End-Expiratory Pressure (PEEP) on Optic Nerve Sheath Diameter (ONSD) in Patients Undergoing Laparoscopic Cholecystectomy Under General Anesthesia: A Prospective Interventional Study

This prospective interventional study will evaluate the effects of applying positive end-expiratory pressure (PEEP) at 10 cmH₂O on optic nerve sheath diameter (ONSD) in patients undergoing elective laparoscopic cholecystectomy under general anesthesia. A total of approximately 40 adult patients (ASA physical status I-II) will be included following informed consent.

ONSD will be measured using a high-frequency linear ultrasound probe at three predefined intraoperative time points: (T0) 10 minutes after initiation of mechanical ventilation, (T1) 10 minutes after pneumoperitoneum creation, and (T2) 30 minutes after pneumoperitoneum creation. Dynamic lung compliance, peak airway pressure (Ppeak), end-tidal CO₂ (EtCO₂), heart rate, mean arterial pressure, and SpO₂ will also be recorded.

The aim is to assess whether the application of PEEP influences intracranial pressure indicators, particularly ONSD, during laparoscopic procedures. The study may provide valuable insights into the neurophysiological effects of intra-abdominal pressure and mechanical ventilation strategies in surgical patients.

Inclusion Criteria:

- Adult patients (age ≥ 18 years)

American Society of Anesthesiologists (ASA) physical status I-III

Scheduled for elective laparoscopic cholecystectomy under general anesthesia

Signed informed consent

Exclusion Criteria:

• resence of acute or chronic eye disease

Uncontrolled hypertension

Asthma or known chronic pulmonary disease

Any neurological disorders

Body mass index (BMI) > 35 kg/m²

Use of medications known to affect intracranial pressure

Refusal to participate after signing informed consent