Both the steep head-down position and pneumoperitoneum increase the intracranial pressure (ICP), and their combination for a prolonged period during laparoscopic radical prostatectomy (LRP) might influence the central nervous system homeostasis. Changes in optic nerve sheath diameter (ONSD) may reflect those in ICP. This study aims to quantify the change in ONSD in response to peritoneal CO2 insufflation and steep Trendelenburg position during LRP. ONSD was measured by ultrasound in 20 patients undergoing LRP and ten awake healthy volunteers. In patients, ONSD was assessed at baseline immediately after induction of general anesthesia in supine position, 10 and 60 min from baseline in a 25° head-down position during pneumoperitoneum, and after deflation of pneumoperitoneum with the patient supine at 0° angle. ONSD in controls was assessed at baseline with the patient lying supine, after 10 and 60 min of 25° head-down position, and 10 min after repositioning at 0° angle. ONSD increased significantly in both patients and controls (p < 0.0001) without between-group differences. The mean increase was 10.3% (95% CI 7.7-12.9%) in patients versus 7.5% (95% CI 2.5-12.6%) in controls (p = 0.28), and didn't affect the time to recovery from anesthesia. In the studied patients, with a limited increase of end-tidal CO2 and airway pressure, and low volume fluid infusion, the maximal ONSD was always below the cut-off value suspect for increased ICP. ONSD reflects the changes in hydrostatic pressure in response to steep Trendelenburg position, and its increase might be minimized by careful handling of general anesthesia.
Trial registration: ClinicalTrials.gov NCT01927380.
Keywords: Intracranial pressure; Laparoscopy; Optic nerve; Pneumoperitoneum; Trendelenburg; Ultrasound.