Admission lactate and short-term mortality in the geriatric ICU: comparison with established severity scores

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.

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 h 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.

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).

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.