Relationship between Preoperative and Postoperative Peripheral Oxygen Saturation and Malignant Brain Edema in Stroke Patients Undergoing Mechanical Thrombectomy

Introduction: As the fifth vital sign, peripheral oxygen saturation (SpO2) remains understudied in acute ischemic stroke (AIS) patients undergoing mechanical thrombectomy (MT). This study aimed to investigate the association between perioperative SpO2 levels and malignant brain edema (MBE) development in MT-treated AIS patients. Methods: We retrospectively analyzed consecutive stroke patients who achieved successful recanalization through MT between May 2017 and February 2023. Noninvasive SpO2 measurements were obtained pre- and postoperatively. Regression analysis was carried out to assess the association between preoperative, postoperative, and combined SpO2 (stratified into four groups based on SpO2 median values: HL, high preoperative/low postoperative; LL, low/low; HH, high/high; and LH, low/high) and MBE. DeLong's test was conducted to compare the predictive value of combined SpO2 with that of preoperative or postoperative SpO2 alone. Results: Among 376 patients, 84 (22.34%) patients developed MBE. Although preoperative SpO2 was not independently associated with MBE (OR: 0.88; 95% CI: 0.78-1.00; p =0.0583), postoperative SpO2 was independently correlated with MBE (OR: 1.48; 95% CI: 1.01-2.18; p =0.0440). The LH group demonstrated 5.33-fold higher MBE risk versus HL (95% CI: 1.80- 15.82; Ptrend =0.0043). Combined SpO2 assessment outperformed preoperative measurements alone (0.6316 vs. 0.5478, p =0.0382) and trended towards superiority over postoperative values (0.6316 vs. 0.6022, p =0.0541). Discussion: Preoperative and postoperative SpO2 exhibit divergent impacts on MBE, likely reflecting distinct pathophysiology. Preoperative hypoxia may exacerbate ischemic core expansion, while postoperative hyperoxia could augment reperfusion injury via reactive oxygen species. The LH pattern (low pre-/high post-MT SpO2) highlights a high-risk phenotype for MBE. Conclusion: Preoperative and postoperative SpO2 differentially influence MBE development, suggesting distinct pathophysiological mechanisms during thrombectomy phases.