Metabolic and Immune Vulnerability in Critically Ill Patients with Diabetes Mellitus

Background and Objectives: Diabetes mellitus is frequently encountered in critically ill patients and is associated with increased short-term mortality. However, the biological and clinical determinants of mortality within the diabetic intensive care unit (ICU) population remain incompletely understood. This study aimed to evaluate laboratory parameters at ICU admission and key early ICU course variables, including acute complications and organ support interventions, associated with short-term ICU mortality in critically ill patients with diabetes mellitus. Materials and Methods: We conducted a retrospective observational cohort study including adult patients with diabetes mellitus admitted to a tertiary care ICU between January and December 2024. Demographic data, laboratory parameters at ICU admission, acute complications, and ICU interventions were collected. Patients were stratified according to ICU outcome (survivors vs. non-survivors). Univariate and multivariate logistic regression analyses were performed to identify independent predictors of ICU mortality. Model performance was assessed using the area under the receiver operating characteristic curve (AUC/ROC), Hosmer–Lemeshow test, and Brier score. Results: A total of 443 critically ill patients with diabetes mellitus were included, of whom 239 (54.0%) died during ICU hospitalization. Non-survivors exhibited higher admission blood glucose, lactate levels, and serum creatinine, as well as lower lymphocyte counts compared to survivors. Acute complications, including sepsis, acute kidney injury, and acute respiratory failure, were significantly more frequent among non-survivors. In multivariate analysis, admission lactate levels (OR = 1.02 per mg/dL increase), mechanical ventilation (OR = 47.30), and hemodialysis (OR = 3.38) remained independently associated with ICU mortality. The predictive model demonstrated good discrimination (AUC = 0.87) and adequate calibration. Conclusions: Critically ill patients with diabetes mellitus who do not survive ICU hospitalization present with early metabolic stress, immune dysregulation, and organ dysfunction. Admission lactate levels and the need for advanced organ support are key predictors of short-term mortality, supporting their role in risk stratification within the diabetic ICU population.