Detection of elevated intracranial pressure in robot-assisted laparoscopic radical prostatectomy using ultrasonography of optic nerve sheath diameter

Robot-assisted laparoscopic radical prostatectomy (RALRP) is becoming an increasingly frequent procedure. Pneumoperitoneum and steep trendelenburg positioning associated with this surgery may increase patient's risk for elevated intracranial pressure (ICP). We conducted a prospective observational trial using ultrasonographic analysis of optic nerve sheath diameter (ONSD) to determine if ICP increased to levels >20 mm Hg during RALRP surgery. The study includes 25 patients, without any history of increased ICP, undergoing RALRP. Ultrasonographic analysis of ONSD was performed immediately after induction of general anesthesia and again at the end of the procedure. A threshold value of ≥5.2 mm for ONSD was used for determination of raised ICP (>20 mm Hg). Age, race, body mass index, American Society of Anesthesiologists Physical Status Classification System class, total intraoperative IV fluids, and surgery duration were recorded, as well as, mean arterial pressure (MAP), end-tidal CO2, and end-tidal isoflurane concentration. Mean preinduction ONSD, in the 25 patients studied, was 4.5+0.5 mm and mean postoperative ONSD was 5.5+0.5 mm. Controlling for preinduction ONSD, postoperative ONSD was significantly associated with MAP (P=0.048) and the association of postoperative ONSD with end-tidal CO2 trended toward significance (P=0.072). This study demonstrates an increase in ONSD in patients undergoing RALRP. These findings confirm ICP rises to ≥20 mm Hg during RALRP surgery. This increase in ICP is significantly associated with increasing MAP. Patients with intracranial pathology should be counseled to the risks RALRP may pose with regard to intracranial hypertension.