Optic nerve sheath diameter remains constant during robot assisted laparoscopic radical prostatectomy

Area of Science:

• Neurosurgery
• Anesthesiology
• Ophthalmology

Background:

• Robot-assisted laparoscopic radical prostatectomy (RALRP) involves CO2 pneumoperitoneum (CO2PP) and head-down positioning.
• These conditions are expected to acutely increase intracranial pressure (ICP).
• Optic nerve sheath diameter (ONSD) measurement offers a non-invasive method to assess ICP changes.

Purpose of the Study:

• To evaluate changes in ONSD during RALRP with CO2PP and head-down positioning.
• To assess the compensatory mechanisms for ICP fluctuations in this surgical context.

Main Methods:

• ONSD was measured using ocular ultrasound in 20 patients undergoing RALRP.
• Measurements were taken at various stages: baseline, post-induction, post-CO2PP, during head-down, post-supine, PACU, and postoperative day one.
• Cerebral perfusion pressure (CPP) was calculated (MAP-CVP).

Main Results:

• ONSD remained unchanged despite increased CVP during head-down positioning.
• CPP decreased but consistently stayed above 60 mm Hg.
• No significant changes in ONSD indicate that cerebrospinal fluid (CSF) compensatory mechanisms were not exhausted.

Conclusions:

• ONSD did not change during head-down positioning in RALRP.
• This suggests that intracranial blood volume does not increase to the point of overwhelming CSF compensatory shifts.
• The findings imply that ICP increases during CO2PP and head-down positioning in RALRP are likely minimal.