The association between endothelial activation and stress Index and the development and prognosis of acute kidney injury in elderly patients with critical illness

This study investigated the link between the endothelial activation and stress index (EASIX) and acute kidney injury (AKI) development and prognosis in elderly critically ill patients. Using the MIMIC-IV database, we conducted a retrospective cohort study including 12,122 ICU patients aged ≥65 years, of whom 9,124 developed AKI. Patients were divided into three groups based on EASIX scores. We compared the baseline characteristics, mortality rates, and clinical outcomes across groups. Multivariable Cox regression analysis assessed the association between EASIX and AKI development and short-term outcomes, adjusting for confounders. Kaplan-Meier curves and subgroup analyses were performed. Dose-response modeling, threshold effect analysis, and E-value analysis were also conducted. Results showed that patients with the highest EASIX scores had significantly higher mortality rates, with HRs for 28-day mortality of 1.69 (95% CI: 1.47-1.95, <i>p</i> < 0.001), in-ICU mortality of 1.55 (95% CI: 1.34-1.79, <i>p</i> < 0.001), and in-hospital mortality of 1.42 (95% CI: 1.13-1.79, <i>p</i> = 0.003). Kaplan-Meier curves indicated lower survival probabilities with higher EASIX values (log-rank <i>p</i> < 0.001). Dose-response analysis revealed a nonlinear relationship with a threshold effect at an EASIX value of around 175. Subgroup analysis found a significant interaction in the CHF subgroup (<i>p</i> < 0.001), suggesting the increased vulnerability to elevated EASIX. In conclusion, elevated EASIX is significantly associated with AKI development and adverse short-term outcomes in elderly critically ill patients, indicating its potential as an index for identifying high-risk patients.