Aim: The deep trendelenburg position and pneumoperitoneum those applied in cases of Robot-Assisted Laparoscopic Radical Prostatectomy (RALRP) operations are thought to increase intracranial pressure. Orbital ultrasonography as a non-invasive measurement of the optic nerve sheath diameter (ONSD) have been reported in recent years as in correlation with intracranial pressure. In this study, RALRP operations done in different intra-abdominal pressures and the affect of the ONSD with different intra-abdominal pressure levels have been shown. Whether changes made in the cognitive functions of patients has been investigated by this likely effect.
Materials and methods: 40patients who RALRP operation planned, ASA physical statusI-II and in ages 50-70 were included to this study. The patients were divided into 2groups; according to insufflation pressure as 10 mmHg (Group I) and 15mmHg (Group II). The optic nerve sheath diameter measuring done for 10 times from the right eye of the patients with its 4 axis by ultrasound; before the induction of anesthesia, 5min after induction, 5min after abdominal insufflation, 5,15,30,60 and 120 min of the trendelenburg position, 5min after intra-abdominal insufflation and trendelenburg terminated and 5min after extubation. Standardized Mini Mental State Examination(SMMSE) was performed 1day before and 3days later the operation. 
Results: There were no differences between the two groups for the operation time and demographical values.ONSD value was significantly (p< 0,05) lower in Group I at the 60. and 120.min of the Trendelenburg position and at the 5.min of returning to supine position.There were no difference between preop and postop SMMSE results for the two groups. Mean airway pressure and ONSD values in deep trendelenburg position during operation has increased in both groups compared with baseline values; but they have decreased back to levels similar to their baseline values at the end of the operation parameters with the supine position.
Conclusion: These results determined that lower intracranial pressure occurs at the low insufflation group by lower ONSD values with the prolongation of the deep trendelenburg position,but this difference did not make a significant difference in terms of cognitive function,which is viewed by the SMMSE.

The effect of pneumoperitoneum and position on the optic nerve sheath diameter during robotic radical prostatectomy: an ultrasonographic evaluation