Reverse Trendelenburg position has been shown to slightly reduce the intracranial pressure associated with pneumoperitoneum. However, there are no studies on the effect of the timing of reverse Trendelenburg position on intracranial pressure. This study will monitor the effect of reverse Trendelenburg position before or after pneumoperitoneum on intracranial pressure and regional cerebral oxygen saturation.

The literature includes studies that investigate the relationship of pneumoperitoneum and different positions with intracranial pressure during laparoscopy. Reverse Trendelenburg position has been shown to slightly reduce the intracranial pressure associated with pneumoperitoneum. However, there are no studies on the effect of the timing of reverse Trendelenburg position on intracranial pressure. This study will monitor the effect of reverse Trendelenburg position before or after pneumoperitoneum on intracranial pressure and regional cerebral oxygen saturation. Ultrasound guided measurement of the optic nerve sheath diameter as a non-invasive method will be used for measurement. The investigators believe reverse Trendelenburg position before pneumoperitoneum may prevent undesired sudden increases in intracranial pressure.

Inclusion Criteria:

• Undergoing laparoscopic cholecystectomy operation
• Age between 18-65
• ASA I-II
• BMI ≤ 35

Exclusion Criteria:

• Ophthalmologic disease and optic nerve pathology
• Increased intracranial pressure
• History of cerebrovascular disease