Sepsis-Associated Acute Kidney Injury and 28-Day Mortality in Critically Ill Patients with Sepsis: A Retrospective Cohort Study

Background/Objectives: We aimed to analyse the development of acute kidney injury (AKI), its association with mortality, and mortality-associated factors in patients admitted to the intensive care unit (ICU) with sepsis. Methods: This retrospective cohort study was conducted on adult patients with sepsis admitted to the ICU of a tertiary-care hospital between January 2023 and December 2023. Demographic, clinical, and laboratory data within the first 24 h of admission to the ICU were recorded. These data were compared between patients with and without sepsis-associated acute kidney injury (SA-AKI). Results: Among 1163 admissions, 185 met the study criteria, and the incidence of SA-AKI was 45.4%. The overall 28-day mortality was 38.4%. Patients with SA-AKI had significantly higher mortality than those without SA-AKI (63.1% vs. 17.8%, p < 0.001). In the multivariable Cox regression analysis, SA-AKI was independently associated with a higher risk of 28-day mortality (HR = 2.87, 95% CI 1.51–5.45, p = 0.001). Among patients with SA-AKI, elevated lactate showed a borderline association with mortality (HR = 1.06 per mmol/L, 95% CI 1.00–1.13, p = 0.053); first-day vasopressor use was not independently associated with mortality after adjustment for illness severity. Conclusions: SA-AKI was independently associated with higher 28-day mortality. Within the SA-AKI subgroup, lactate showed only a borderline association with mortality, whereas first-day vasopressor use appeared to reflect illness severity.