Effect of inspired oxygen fraction during anesthesia on inflammation and antioxidant enzyme activity in the mouse cortex and hippocampus.

Introduction: Although high inspired oxygen fraction (FiO₂) is used during anesthesia to prevent hypoxemia, the effect of different oxygen fraction on the brain remains unclear. This study aims to evaluate whether different inspired oxygen fractions (FiO₂ 30% vs. 80%) during anesthesia affect inflammation and antioxidant enzyme activity in the cortex and hippocampus of young and aged mice. Methods: Young and old mice were anesthetized with sevoflurane at FiO₂ 30% or 80% for 3 h. Mice in the control group were exposed to medical air (FiO₂ 21%) for 3 h. Cytokine and superoxide dismutase (SOD) assays were performed on the cortex and hippocampus samples after anesthesia. Results: The IL-1β level in the hippocampus was significantly higher in the FiO₂ 80% group compared with controls [5.0 (4.0-6.9) pg. mL Discussion: Only 80% oxygen increased hippocampal IL-1β compared with controls, suggesting region-specific vulnerability to oxygen-induced neuroinflammation. However, no significant differences between FiO₂ levels (30% vs. 80%) indicate a limited neuroinflammatory impact under 3 h of anesthesia. Further studies with longer exposure and surgical conditions are needed to clarify the clinical implications.