Comparison of the Effects of Different PEEP Values With USG on Optic Nerve Sheath Diameter (ONSD), Diaphragmatic Thickness ,and Lung Score in Laparoscopic Surgery Patients

Laparoscopic surgeries are now becoming increasingly common compared to traditional laparotomies, as they have advantages such as more minimal scarring, shorter hospital stay, fewer complications, and early mobilization. In these surgeries, pneumoperitoneum provided with carbon dioxide (CO2) has many effects on the cardiovascular, pulmonary, renal, metabolic and cerebral systems. Pulmonary compliance and functional residual capacity decrease due to pnemoperitoneum, ventilation/perfusion mismatch occurs, and as a result, hypoxemia may occur. A minimum of 4-6 cm H20 positive end-expiratory pressure (PEEP) should be applied to all intubated patients under general anesthesia to reduce postoperative pulmonary complications (especially atelectasis) and prevent ventilation/perfusion mismatch and hypoxemia. The optic nerve sheath is an extension of the dura mater and the subarachnoid space is continuous with the intracranial subarachnoid space. Therefore, non-invasive monitoring of the increase in intracranial pressure (ICP) can be achieved by measuring the optic nerve and sheath diameter with ultrasound. When ICP is > 20 mm Hg, measuring the optic nerve sheath diameter (ONSD) between 5.2 and 5.9 mm has a sensitivity of 74-95% and a specificity of 74-100%. Since ONSD measurement with ultrasound is an easily applicable technique, it is useful in monitoring intracranial pressure changes based on the optic nerve diameter during intraoperative changes (trendelenburg/reverse trendelenburg position, pneumoperitoneum , PEEP in mechanical ventilation).