Nonlinear relationship between stress hyperglycemic ratio and prognosis in patients with cardiac surgery-related kidney injury: a retrospective cohort study

The prognostic role of the stress-induced hyperglycemia ratio (SHR) in patients with acute kidney injury related to cardiac surgery has not been fully explored. This study aims to examine the association between the SHR index and mortality in patients with cardiac surgery-associated acute kidney injury (CS-AKI). Data for this research were collected from the MIMIC database. This study investigated the relationship between SHR and prognosis of CS-AKI patients by survival analysis, restricted cubic lines, and subgroup analysis. In the final analysis, 3,249 patients were categorized into four groups based on the quartiles of the SHR. Multivariable Cox proportional hazards regression analysis demonstrated that patients in the highest quartile (Q4) had a significantly increased risk of mortality compared to those in the lower three quartiles (Q1-Q3) (<i>p</i> < 0.005). Receiver operating characteristic (ROC) curve analysis indicated a U-shaped relationship between SHR and patient mortality, with both low and high SHR values associated with increased risk. Incorporation of SHR into existing prognostic models (SHR+SAPS II, SHR+APACHE III, and SHR+SOFA) led to improved discriminative performance, as reflected by increased area under the curve (AUC) values. Additionally, the inclusion of SHR significantly enhanced model performance as demonstrated by net reclassification improvement (NRI) and integrated discrimination improvement (IDI) metrics (<i>p</i> < 0.046). The findings of this study indicate a U-shaped association between the SHR and prognosis in patients with CS-AKI. However, only elevated SHR values were independently associated with an increased risk of mortality after adjustment for confounding variables.