Objective:To explore the application value of regional oxygen saturation (rSO 2) level in the prognosis evaluation of patients with acute lower limb ischemia (ALLI). Methods:Retrospective analysis of clinical data of 82 ALLI patients admitted to the ICU of Xinjiang Uygur Autonomous Region People's Hospital from June 2021 to June 2022. The subjects were divided into event group and non-event group according to the incidence of adverse events during the follow-up. The general clinical data of the two groups were compared. Multiple stepwise linear regression was used to analyze the independent related factors of rSO 2. Multivariate Cox regression was used to analyze independent risk factors of adverse events. Receiver operating characteristic (ROC) curve was used to obtain the optimal cut-off value of rSO 2 prediction adverse events. The subjects were divided into high-value group and low-value group according to the optimal cut-off value. Kaplan-Meier curve was used to analyze the difference in survival rate between groups during the follow-up. Results:A total of 82 ALLI patients were included in this study, and the incidence of adverse events during follow-up was 25.6% (21 cases). The rSO 2 of four periods and maximum, minimum, average and ankle-brachial index in the event group were significantly lower than those in the non-event group. The troponin I, troponin T, myoglobin, creatine kinase, C-reactive protein, and lactate in the event group were significantly higher than those in the non event group ( P?0.05). Multiple stepwise linear regression analysis showed that: C-reactive protein ( β=-0.320, P=0.002), lactate ( β=-0.262, P=0.009), troponin Ⅰ ( β=-0.230, P=0.025), and smoking history ( β=-0.211, P=0.034) were all independent predictors of rSO 2. Multivariate Cox regression analysis showed that 24 h rSO 2 (mean) was an independent influencing factor for adverse events in ALLI patients (adjusted HR=0.67, 95% CI:0.54-0.83, P<0.001). The 24 h rSO 2 (mean) was good in predicting the incidence of adverse events at 30, 60, and 90 days in ALLI patients (AUC were 0.934, 0.867 and 0.823), and the corresponding optimal cut-off values of rSO 2 were 59.36, 59.03 and 59.03. The sensitivity and specificity to predict adverse events in ALLI patients were 85.7% and 85.3% when the 24 h rSO 2 (mean) was 59.36 as the best cut-off value. According to the optimal cut-off , the subjects were divided into high value group (rSO 2>59.36%, 59 cases) and low value group (rSO 2≤59.36%, 23 cases), Kaplan Meier survival curve analysis showed that there was significant difference in event free survival between the two groups ( P<0.001), the high value group significantly better than the low value group. Conclusion:The 24 h rSO 2 (mean) is an independent influencing factor for adverse events in ALLI patients, and has good predictive value for prognosis.