Extremely low regional cerebral oxygen saturation during general anesthesia in severe sepsis: A report of two cases

Near-infrared spectroscopy-based cerebral oximetry is commonly used to detect cerebral hypoxia during anesthesia. However, the clinical significance of extremely low regional cerebral oxygen saturation (rSO₂) in noncardiac surgery in severe sepsis remains unclear. We report two patients with severe sepsis who underwent emergency noncardiac surgery under general anesthesia. In both cases, systemic parameters, including arterial blood pressure, arterial oxygen saturation, and bispectral index, were within clinically acceptable ranges. Nevertheless, intraoperative rSO₂ decreased to 15% (the lowest measurable value) bilaterally and persisted throughout the surgery. Both patients developed refractory shock and severe metabolic derangements and died shortly thereafter. We report these cases to highlight an unusual monitoring pattern in which extreme rSO₂ depression occurred in the context of severe sepsis and to raise the question of its physiological significance and clinical implications.