Cerebral hemodynamics, autoregulation, and neurocognitive outcomes during Trendelenburg positioning in robot-assisted abdominopelvic surgery: a narrative review.

Robot-assisted abdominopelvic surgery often combines carbon dioxide pneumoperitoneum with steep Trendelenburg positioning. Together, these exposures can alter arterial inflow, venous outflow, intracranial downstream pressure, and systemic hemodynamics. We conducted a structured search of PubMed, Embase, Web of Science Core Collection, and the Cochrane Library from inception through 24 August 2026 and used narrative synthesis to integrate direct human evidence from robotic surgery with indirect evidence from other clinical settings. Fifty-five eligible full-text reports, representing 48 independent studies, were included. The direct evidence consisted mainly of small studies of robot-assisted laparoscopic radical prostatectomy. Pneumoperitoneum may increase systemic vascular resistance, so mean arterial pressure can remain stable or rise even while cardiac output and cerebral blood flow fall. Head-down tilt, higher thoracoabdominal pressure, and impaired jugular drainage may also increase central venous and intracranial pressure, reducing effective cerebral perfusion pressure. Near-infrared spectroscopy, optic nerve sheath diameter, mean velocity index, cerebral oximetry index, and direct flow measurements interrogate different parts of this physiology. When downstream pressure changes over time, a low or negative autoregulation index cannot exclude restricted cerebral perfusion. No evidence shows that raising mean arterial pressure alone or targeting a specific autoregulation threshold improves neurocognitive outcomes. Perioperative management should integrate brain-level arterial pressure, cardiac output, carbon dioxide, and venous drainage while addressing modifiable surgical factors. Future studies should standardize operative exposure, synchronize arterial and venous measurements, and use consistent neurocognitive outcomes.