Assessment of Amplitude and Temporal Differences of Cerebral Oxygen Saturation in Response to Hypotension Across Multiple Cerebrovascular Territories During Shoulder Surgery.

Introduction: Current commercial cerebral oximeters only monitor the frontal lobes, however, some cerebrovascular territories may experience ischemia while others remain well perfused. This pilot study used a novel, high-density, dual-wavelength, time-resolved functional cerebral oximeter (Kernel Flow) with 2000 channels to assess the regional differences of cerebral oxygenation (StO2) in response to hypotension across different vascular territories during shoulder surgery in the beach chair position.

Methods: Twenty-seven adult patients were monitored, recording blood pressure, heart rate, regional cerebral oxygen saturation, and other vital parameters. For each hypotensive event, regional cerebral oxygen saturations were compared against each other using a mixed-effect model. Data processing involved moment analysis and MATLAB-based detrending to correct for temperature-induced signal drifts.

Results: Twenty-one hypotensive events were excluded due to poor data quality. Results from 16 hypotensive events in 4 patients indicated no significant temporal or amplitude differences in StO2 across 8 cerebrovascular territories. The mean±SD decrease in systolic blood pressure was 30.2±18.3 mm Hg, resulting in a mean cerebral desaturation across all territories of 3.3%±1.8%. There were no statistically significant temporal or magnitude differences between different vascular territories, though large variabilities were observed.

Conclusions: Despite limitations, such as small sample size and the exclusion of large number of events, this pilot study demonstrates that StO2 changes in response to hypotension in multiple brain regions can be measured and compared during surgery, providing insights and facilitating investigation of the selective vulnerability of brain regions. Future exploration will enhance our understanding of cerebral ischemia pathophysiology and perioperative stroke.