Methods Ninety patients with septic shock undergoing shock resuscitation in the intensive care unit were selected as the study subjects. According to their 28-day survival status, the patients were divided into a survival group (n = 47) and a death group (n = 43). The basic clinical data of patients were collected. The rSO₂ was continuously and dynamically monitored, and minimum rSO₂ (rSO₂min), maximum rSO₂ (rSO₂max), average rSO₂, and rSO₂ variability were calculated. Multivariate logistic regression analysis was applied to analyze the risk factors affecting the death of patients with sepsis within 28 days, Kaplan-Meier curve was used for survival analysis, ROC curve was employed to analyze the diagnostic value of average rSO₂ value and rSO₂ variability for 28-day mortality in sepsis patients.

Results The acute physiology and acute physiology, age, chronic health evaluation Ⅱ (APACHE Ⅱ) score, sequential organ failure assessment score, white blood cell count, and lactate level of patients in the death group were significantly higher than those in the survival group (P ＜ 0.01), and the oxygenation index was significantly lower than that in the survival group (P ＜ 0.01). An increasing trend in rSO₂ of patients after 2, 4, and 6 hours of treatment was found in the two groups, and the rSO₂ in the survival group increased rapidly with time, which was significantly higher than that in the death group (P ＜ 0.01). There was no statistically significant difference in rSO₂min and rSO₂max of patients between the two groups within 6 hours of treatment (P ＞ 0.05). The average rSO₂ of patients in the death group was significantly lower than that in the survival group (P ＜ 0.01), and the rSO₂ variability was significantly higher than that in the survival group (P ＜ 0.01). Multivariate logistic regression analysis showed that APACHE Ⅱ score, oxygenation index, and average rSO₂ were independent risk factors for mortality within 28 days in sepsis patients (P ＜ 0.01). Kaplan-Meier curve analysis showed that the 28-day survival rate of patients in the rSO₂ ≥ 60% group was 65.00% (38/50), which significantly higher than 22.50% (9/40) in the rSO₂ ＜ 60% group (χ² = 10.08, P ＜ 0.01). The AUC of the combined diagnosis of average rSO₂ and rSO₂ variability for 28-day mortality in sepsis patients was 0.911 (95% CI: 0.833–0.961), with a sensitivity of 81.40%, and specificity of 91.49%, and the combined diagnostic efficacy was better than that of average rSO₂ and rSO₂ variability alone (Z = 2.07, 1.97, P ＜ 0.05).

Conclusions The low rSO₂ level is related to poor prognosis of septic shock. Early monitoring of rSO₂ level has certain clinical significance in predicting the prognosis of septic shock patients.