Ventilation Modes Effect on Intracranial Pressure During Laparoscopic Colectomy by Optic Nerve Sheath Diameter

Patients who undergo laparoscopic surgery often experience increased intracranial pressure (ICP). In laparoscopic colectomy surgery, the duration always exceeds 2h with more liability to changes in arterial blood gases, hemodynamics, also the patient is in Trendelenburg position about 30° head down, Trendelenburg position is believed to create changes in hemodynamics, respiratory mechanics, metabolic response, and ICP as it affects vital organs especially if steep positioning. Various modes of mechanical ventilation have been experimented to achieve good intraoperative oxygenation which may cause changes in arterial blood gas values and hemodynamic parameters that might lead to changes in the ICP. In this study we will measure ONSD, basal, intraoperative, and in the PACU to evaluate the effect of different ventilation modes (both VCV mode and PCV-VG mode) on intracranial pressure.