Admission Lactate and Short-Term Mortality in the Geriatric ICU: Comparison with Established Severity Scores

Aim: This study aims to investigate the prognostic value of admission lactate level in predicting 28-day mortality among geriatric patients admitted to the intensive care unit (ICU) and to compare its performance with established severity scores, including APACHE II and SOFA. Materials and methods: In this retrospective cohort study, data of patients aged ≥ 65 years who were admitted to a tertiary ICU between December 2024 and June 2025 were analyzed. Patients with ICU stays < 24 hours or incomplete records were excluded. Demographic characteristics, comorbidities, admission lactate, APACHE II, and SOFA scores were recorded. The primary outcome was the association between admission lactate and 28-day mortality. Secondary outcomes included ICU length of stay, mechanical ventilation duration, and comparative prognostic accuracy of lactate versus APACHE II and SOFA. Results: A total of 241 patients were included. The 28-day mortality rate was 32.8%. Non-survivors had significantly higher admission lactate levels compared to survivors (6.29 ± 5.42 vs. 2.44 ± 1.80 mmol/L, p < 0.001). In multivariable logistic regression, admission lactate remained an independent predictor of mortality after adjustment for age, sex, comorbidity, and APACHE II (OR 1.29, 95% CI 1.09–1.52, p = 0.003). ROC analysis showed that lactate predicted 28-day mortality with an AUC of 0.77, compared to 0.92 for APACHE II and 0.88 for SOFA. Mortality increased across lactate categories: 14.2% (< 2 mmol/L), 27.8% (2–4 mmol/L), and 62.5% (> 4 mmol/L) (p < 0.001). Conclusion: Admission lactate is a simple and readily obtainable biomarker that independently predicts short-term mortality in geriatric ICU patients. While not outperforming established severity scores, lactate provides immediate risk stratification at the bedside and may aid clinical decision-making in this vulnerable population.