Intracranial pressure is known to increase during robot-assisted laparoscopic radical prostatectomy (RALRP) due to steep trendelenberg position. Measurement of optic nerve sheath diameter (ONSD) is a indirect method which can assess the degree of intracranial pressure.

This study is designed to measure the ONSD during RALRP under regulation of arterial pressure.

During last decades, RALRP has been advocated due to the advantages of short hospital stay, reduced blood loss during surgery, less postoperative pain and complication. During RALRP, steep trendelenberg postion and pneumoperitoneum are required essentially, and this is for the acquisition of adequite surgical field. However, such position and pneumoperitoneum can result in harmful hemodynamic change. Previous study demonstrated that patients of RALRP showed 12.5% increase of ONSD.

The relationship of ONSD and increase of intracranial pressure has been proved previously through many studies. Recent meta analysis showed that ONSD measurement for the monitor of ICP demonstrated that sensitivity 0.9, specificity 0.85 and ROC cuve 0.983.

In addition, increase of ONSD during RALRP can be affected by the degree of arterial pressure and end tidal CO2 increase.

This study is designed to see the effect of arterial pressure regulation on the increase of ONSD

Inclusion Criteria:

• Prostate cancer receiving RALRP

Exclusion Criteria:

• glaucoma
• intracranial tumor
• previous disease elevating intracranial pressure