Integrating blood lactate levels and nutritional status in early risk stratification for delirium and mortality in elderly septic patients: A retrospective cohort study

Delirium and mortality are major complications in elderly septic patients. Current prediction tools, like Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores, often overlook metabolic stress and nutritional deficits. This study assessed the combined prognostic value of blood lactate (Lac), Mini Nutritional Assessment-Short Form (MNA-SF), and SOFA scores for delirium and 28-day mortality. A cohort of 304 elderly septic patients was retrospectively analyzed. Key predictors (Lac, MNA-SF, SOFA) were evaluated using Restricted Cubic Spline (RCS) and logistic regression. Receiver operating characteristic (ROC) curves and AUC values quantified predictive models, while mediation analysis explored the indirect effects of Lac on outcomes. Delirium was observed in 36.2% of patients, with a 28-day mortality rate of 24.7%. Elevated lactate (≥4.23 mmol/L) correlated with worse MNA-SF scores (r = -0.284, P < .05). RCS showed a nonlinear association of Lac with delirium and mortality, with risks sharply rising beyond 4 mmol/L. Independent Lac (OR > 3.0 at 4 mmol/L) and combined Lac-MNA-SF-SOFA models yielded high predictive accuracies for both delirium (AUC = 0.922) and mortality (AUC = 0.853). Mediation analysis demonstrated that nutritional status (MNA-SF) and organ dysfunction (SOFA) explained 33.85% of Lac effect on delirium and 54.30% on mortality. Integrating Lac, MNA-SF, and SOFA scores enhances early stratification of delirium and mortality risks in septic elderly patients. Interventions focusing on metabolic and nutritional optimization can significantly improve prognosis. Routine Lac and MNA-SF screening offer actionable insights for personalized care, helping reduce complications, shorten hospital stays, and improve survival rates in this vulnerable population.