Abstract: Objective  To investigate the 30 day prognosis of adult patients who underwent continuous renal replacement therapy (CRRT) after cardiac surgery and developed sepsis-associated acute kidney injury (SA-AKI).  Methods  A retrospective cohort study was conducted, collecting clinical data from 239 adult patients who underwent CRRT at Guangdong Provincial People's Hospital from March 2023 to May 2024. Patients were divided into two groups based on whether they developed sepsis-associated acute kidney injury within 7 days after cardiac surgery: Acute kidney injury (AKI) group and SA-AKI group.  Results  A total of 239 adult patients who underwent cardiac surgery were included, with an average age of 57.4±13.5 years, and 157 males (65.7%). The Sequential organ failure assessment (SOFA) score was higher in the SA-AKI group compared to the AKI group, 11.0±3.63 vs. 9.45±3.89, (t=-2.534, P=0.014). The overall mortality rate was 31.4% (75/239), with an average treatment time of CRRT and the interquartile range was 8.0 (3.0,17.0) days. The mortality rate of patients in the SA-AKI group was significantly higher than that in the AKI group, 62.8% vs. 24.5%, (χ2=-4.747, P＜0.001). Kaplan-Meier survival analysis log-rank test showed that the cumulative mortality rate in the SA-AKI group was significantly higher than in the AKI group, HR (95%CI) =1.959 (1.220～3.145), (P=0.004). The repeated-measures analysis showed that there was a significant difference in SOFA scores between the SA-AKI group and the AKI group (P=0.004, F=8.135), and a significant time trend was also observed (P＜0.001, F=4.441).  There was a trend towards lower blood lactate levels in both groups, with no significant inter-group differences (P=0.215，F=1.543). There was a significant difference in mean arterial pressure between the SA-AKI group and the AKI group (P=0.002, F=9.028), while the time trend was not significant (P=0.739, F=0.589). Patients in the mortality group had higher SOFA scores than those in the survival group (P＜0.001, F=61.036). The blood lactate levels were higher in the mortality group than that in the survival group (P＜0.001, F=14.853). Additionally, the mean arterial pressure was lower in the mortality group compared with the survival group (P＜0.001, F=45.056).  Conclusion  Patients who developed sepsis-associated acute kidney injury after cardiac surgery have a significantly increased 30-day mortality risk. During the first week of CRRT treatment, it is important to monitor changes in the condition, especially to strengthen monitoring of trends in SOFA scores, lactate levels, and hemodynamic indicators.

Key words: Sepsis-associated acute kidney injury, Cardiac surgery, Continuous renal replacement therapy, Prognosis