Increase in intracranial pressure during carbon dioxide pneumoperitoneum with steep trendelenburg positioning proven by ultrasonographic measurement of optic nerve sheath diameter

Purpose: The purpose of this study was to assess the extent of the increased intracranial pressure (ICP) resulting from CO₂ pneumoperitoneum and steep Trendelenburg positioning using ultrasonographic measurement of optic nerve sheath diameter (ONSD) in patients undergoing robot-assisted laparoscopic radical prostatectomy (RALRP). Patients and Methods: Twenty patients who underwent elective RALRP were enrolled in this study. ONSD and regional cerebral oxygen saturation (rSO₂) were investigated noninvasively using ocular ultrasonography and near-infrared spectroscopy before anesthesia (T0), 10 minutes after anesthesia induction in the supine position (T1), 10 and 30 minutes after CO₂ pneumoperitoneum with 30-degree Trendelenburg positioning (T2 and T3), and after returning to supine position without CO₂ pneumoperitoneum at the conclusion of the RALRP (T4). Results: The mean values of ONSD at all time points (T1, T2, T3, and T4) after general anesthesia significantly increased compared with that before general anesthesia (T0). During CO₂ pneumoperitoneum with 30-degree Trendelenburg positioning (T2, T3), a significant increase of 12.5% in ONSD was observed in comparison with ONSD after anesthesia induction in the supine position without CO₂ pneumoperitoneum (T1). Three patients had an ONSD value equivalent to an ICP above 20 mm Hg, and these patients did not experience a decrease of rSO₂ or any neurologic complications. Conclusions: In patients undergoing RALRP, the increase of 12.5% in ONSD during CO₂ pneumoperitoneum with steep Trendelenburg positioning was observed and thus the increase of ICP corresponding to this change of ONSD could be predicted. In 15% of the enrolled patients, ONSD increased by values equivalent to an ICP above 20 mm Hg without a deterioration of rSO₂ or any neurologic complications.