The Preconditioning Effect of Normobaric Hyperoxia on Postoperative Cognitive Dysfunction After Repeated Anesthesia in Rats

Objective: This study aimed to evaluate the neuroprotective effect of normobaric hyperoxia preconditioning on postoperative cognitive dysfunction following repeated sevoflurane anesthesia in a rat model.Method: Twenty-four male Sprague-Dawley rats were randomly assigned to four groups (n=6/group): control, normobaric hyperoxia, sevoflurane, and normobaric hyperoxia followed by sevoflurane.Rats in the hyperoxia groups received 95% oxygen for 3 hours on alternate days for 1 week.Rats in the sevoflurane groups were exposed to 2.9% sevoflurane for 2 hours daily over 5 consecutive days.Cognitive performance was assessed using the Morris Water Maze test.Hippocampal tissues were examined histopathologically for signs of neuronal damage and apoptosis.Results: The sevoflurane group exhibited significantly impaired learning and memory performance compared to the control group (p<0.01).Rats preconditioned with hyperoxia before sevoflurane exposure showed significantly improved escape latency and platform crossing performance compared to the sevoflurane-only group (p<0.05).Histopathological analysis revealed marked hippocampal neuronal degeneration in the sevoflurane-only group, which was substantially reduced in the combined treatment group.No significant neuronal damage was observed in the control or hyperoxia-only groups.Conclusion: Preconditioning with normobaric hyperoxia may mitigate hippocampal neuronal injury and cognitive dysfunction associated with repeated sevoflurane exposure.These preliminary findings highlight the potential neuroprotective effect of hyperoxic preconditioning and support the need for further research with larger cohorts and molecular-level validation.