Time-weighted lactate and glucose–lactate ratio outperform static values in ICU mortality prediction after traumatic brain injury: a retrospective cohort study

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BACKGROUND: Traumatic brain injury (TBI) is a major cause of trauma-related deaths. Systemic glucose and lactate levels reflect secondary metabolic derangements over time; however, most prognostic models rely on admission values. This study compared static and longitudinal indices of glucose, lactate, and their ratio in relation to ICU mortality. METHODS: This retrospective single-center study analyzed 479 non-diabetic adult patients with TBI admitted to a German university ICU (2013-2023). After 1:2 severity-balanced, outcome-stratified propensity score matching, 229 patients (150 survivors, 79 non-survivors) were included. Indices comprised admission values, means, clearance, time-weighted averages, variability, and dysglycemic burden. Outcome was ICU mortality, assessed using regression, mixed-effects modeling, and ROC analysis. RESULTS: Longitudinal indices showed stronger associations. Time-weighted average lactate was the best independent predictor (OR 14.70, 95% CI [5.41-39.98], p < 0.001, AUC 0.73). Time-weighted average glucose-lactate ratio also independently predicted ICU mortality (OR 0.75, 95% CI [0.66-0.86], p < 0.001). Non-survivors exhibited persistently higher glucose, lactate and lower ratios, with lactate significantly elevated on all first ten ICU days (all p < 0.05). Admission values, clearance and variability were not predictive after adjustment. CONCLUSIONS: In critically ill non-diabetic patients with TBI, longitudinal time-weighted average lactate significantly outperformed admission values and glucose metrics for predicting ICU mortality in a severity-balanced cohort; the glucose-lactate ratio was associated but did not surpass lactate. These findings underscore the importance of longitudinal monitoring and support prioritizing lactate in multiparametric prognostic model to account for secondary injuries. Prospective validation is warranted to confirm external validity and assess therapeutic implications.

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