Ocular blood flow in steep Trendelenburg positioning during robotic-assisted radical prostatectomy

Several ischemic optic neuropathies that occurred during robotic-assisted laparoscopic radical prostatectomy (RALRP) have been reported to be due to the Trendelenburg position, which lowers ocular perfusion pressure (OPP). We examined changes in pulsatile ocular blood flow (POBF) and its correlation with OPP during RALRP in the steep Trendelenburg position.

Pulsatile ocular blood flow and intraocular pressure (IOP) were measured in 50 patients by the OBF Langham System 5 times during RALRP. The mean arterial blood pressure (MAP), heart rate, plateau airway pressure, and end-tidal CO₂ (EtCO₂) at each time point were recorded. Ocular perfusion pressure was calculated from simultaneous IOP and MAP measurements.

Pulsatile ocular blood flow was 15.53 ± 3.32 µL/s at T₀, 18.99 ± 4.95 µL/s at T₁, 10.04 ± 3.24 µL/s at T₂, 11.45 ± 3.02 µL/s at T₃, and 15.07 ± 3.81 µL/s at T₄. Ocular perfusion pressure was 70.15 ± 5.98 mm Hg at T₀, 64.21 ± 6.77 mm Hg at T₁, 57.71 ± 7.07 mm Hg at T₂, 51.73 ± 11.58 mm Hg at T₃, and 64.21 ± 12.37 mm Hg at T₄. Repeated-measures analysis of variance on POBF and OPP was significant (p>0.05). This difference disappeared when the correlation between MAP and POBF, EtCO₂ and POBF, and EtCO₂ and OPP were considered, while correlation between MAP and OPP confirmed the difference. The regression analysis between POBF and OPP showed a statistically significant difference at T₀ and T₃ (r = 0.047, p = 0.031 and r = 0.096, p = 0.002, respectively).

Pulsatile ocular blood flow and OPP reached the lowest level at the end of surgery.