Combined metabolic risk and admission lactate-to-bicarbonate ratio in critically ill children: a retrospective pediatric ıntensive care cohort study.

Early identification of high-risk children at pediatric intensive care unit (PICU) admission is essential. This study evaluated the association of admission combined acidosis-hyperlactatemia risk classification and lactate-to-bicarbonate ratio (LBR) with PICU mortality and organ support requirements. This retrospective cohort study included children aged 1 month to 18 years admitted to a tertiary PICU between January 2022 and May 2025 who had lactate and bicarbonate values available from blood gas analysis within the first 24 h. Metabolic acidosis was defined as pH ≤ 7.30 and/or base excess ≤  - 7 mmol/L, and hyperlactatemia as lactate > 2.3 mmol/L. Patients were classified as low risk, intermediate risk, or high risk according to the presence of neither, either, or both abnormalities. The primary outcome was PICU mortality. A total of 1,636 patients were included, and PICU mortality was 7.3%. The low-, intermediate-, and high-risk groups included 874 (53.4%), 569 (34.8%), and 193 (11.8%) patients, respectively. Mortality increased progressively across risk groups from 3.4% to 7.0% and 25.9% (p < 0.001). Similar increases were observed for invasive mechanical ventilation, inotrope/vasopressor use, continuous renal replacement therapy, acute kidney injury, and plasma exchange (all p < 0.001). The combined metabolic risk model showed moderate discrimination for PICU mortality (AUC 0.710), comparable to lactate (AUC 0.707) and LBR (AUC 0.700), while PRISM showed the highest discrimination (AUC 0.820). After PRISM adjustment, high-risk status remained independently associated with mortality (adjusted OR 3.31, 95% CI 1.86-5.88; p < 0.001), whereas LBR showed borderline significance (adjusted OR 2.48, 95% CI 0.96-6.44; p = 0.062).

conclusionThe coexistence of admission hyperlactatemia and metabolic acidosis identified a high-risk phenotype associated with higher mortality and greater organ support requirements. The combined metabolic risk classification may support early bedside risk assessment, whereas LBR should be interpreted as a complementary marker rather than a prognostic measure superior to lactate or validated severity scores. WHAT IS KNOWN: • Lactate and acid-base parameters are associated with illness severity and adverse outcomes in critically ill children. • Validated severity scores remain the standard approach for mortality risk assessment in the PICU. WHAT IS NEW: • The coexistence of admission hyperlactatemia and metabolic acidosis identified a high-risk phenotype with substantially increased PICU mortality and organ support requirements. • LBR showed mortality discrimination similar to lactate alone and should be interpreted as a complementary rather than superior prognostic marker.