Lactate Clearance as a Prognostic Marker in Severe Trauma: A Retrospective Cohort Study

Background/Objectives: Lactate is a key biomarker of tissue hypoperfusion in severe trauma. While admission lactate is widely used, the prognostic value of delayed lactate clearance remains a subject of ongoing investigation, notably due to the inherent risk of survivorship bias. This study assessed the association between lactate kinetics and in-hospital mortality in a cohort of severely injured patients admitted to the intensive care unit. Methods: We conducted a single-center retrospective cohort study including adult patients (≥18 years) admitted to the ICU for severe trauma between January 2018 and December 2022. Arterial lactate was measured at H0, H4 (±1 h), and H12 (±1 h). Lactate clearance (LC) was calculated using the formula: LC (%/h) = [(Lactate_t1 - Lactate_t2)/Lactate_t1] × (1/Δt) × 100, where positive values indicate decreasing lactate (clearance) and negative values indicate worsening lactatemia. LC was calculated over H0-H4, H0-H12, and H4-H12. Among the 38 patients who died before 12 h and were excluded from the LC H0-H12 analysis, non-survivors were significantly older, had higher severity scores, and presented more frequently with hemorrhagic shock. Predictive performance was evaluated using ROC curves and multivariate logistic regression. The composite prognostic score was assessed using bootstrap internal validation (1000 resamples) to provide an optimism-adjusted AUC estimate. Results: Among 318 patients (median age 36 years; 86.5% male), hyperlactatemia (>2.2 mmol/L) was present in 70.1% at admission and persisted in 39.9% at 12 h. Non-survivors exhibited higher lactate levels and lower LC at all time points. LC H0-H12 demonstrated the best predictive performance for in-hospital mortality (AUC = 0.75; 95% CI [0.69-0.81]; p < 0.001). For early mortality (≤48 h), LC H0-H12 achieved an AUC of 0.80 (95% CI [0.71-0.89]; p < 0.001). A composite prognostic score incorporating age >60 years, GCS ≤ 7, prothrombin time ≤ 55%, pH ≤ 7.29, and LC H0-H12 > -2.93 %/h demonstrated good discrimination (AUC = 0.84; optimism-adjusted AUC = 0.82). Conclusions: Lactate levels and 12 h lactate clearance are valuable prognostic markers in severe trauma. Given the inherent survivorship bias affecting the LC H0-H12 analysis, its prognostic performance should be interpreted with appropriate caution and within a multimodal clinical assessment. The proposed composite score is promising but requires prospective external validation before clinical implementation.