Ultrasonographic Measurement of the Optic Nerve Sheath Diameter and Its Association With Eyeball Transverse Diameter in Robot-assisted Laparoscopic Radical Prostatectomy

Robot-assisted laparoscopic radical prostatectomy (RALRP) is becoming a popular procedure due to its unique advantages.

Despite these advantages, pneumoperitoneum and steep trendelenburg position are associated with hemodynamic instability and elevated intracranial pressures (ICP).

Ultrasonographic measurement of optic nerve sheath diameter (ONSD) is an indirect but also a generally accepted reliable and noninvasive measurement of elevated ICP. However, optimal cut-off values are highly inconsistent due to multiple factors (gender, height, weight). To eliminate the effects of these factors on the results; a ratio should be established in patients known to have elevated ICPs.

In a recent study ONSD/ eyeball transverse diameter(ETD) in healthy volunteers in a specific population was established.

60 patients without any history of ICP undergoing RALRP will be enrolled to the study. Ultrasonographic measurement of ONSD and ETD will be performed 10 minutes after induction of general anesthesia, 10 minutes after CO2 pneumoperitoneum with trendelenburg positioning and measurements will be repeated hourly and at last after returning to supine position without CO2 pneumoperitoneum at the end of the procedure.

Hemodynamic variables and BIS values on this specific times will be recorded and an arterial sample will be obtained.