Repeat lactate level predicts mortality better than rate of clearance

BACKGROUND: Lactate clearance has been developed into a marker of resuscitation in trauma, but no study has compared the predictive power of the various clearance calculations. Our objective was to determine which method of calculating lactate clearance best predicted 24-hour and in-hospital mortality after injury. STUDY DESIGN: Retrospective chart review of patients admitted to a Level-1 trauma center directly from the scene of injury from 2010 to 2013 who survived >E15 min, had an elevated lactate at admission (≥3 mmol/L), followed by another measurement within 24 h of admission. Lactate clearance was calculated using five models: actual value of the repeat level, absolute clearance, relative clearance, absolute rate, and relative rate. Models were compared using the areas under the respective receiver operating curves (AUCs), with an endpoint of death at 24 h and in-hospital mortality. RESULTS: 3910 patients had an elevated admission lactate concentration on admission (mean = 5.6 ± 3.0 mmol/L) followed by a second measurement (2.7 ± 1.8 mmol/L). Repeat absolute measurement best predicted 24-hour (AUC = 0.85, 95% CI: 0.84–0.86) and in-hospital death (AUC = 0.77; 95% CI, 0.76–0.78). Relative clearance was the best model of lactate clearance (AUC = 0.77, 95% CI: 0.75–0.78 and AUC = 0.705, 95% CI: 0.69–72, respectively) (p < 0.0001 for each). A sensitivity analysis using a range of initial lactate measures yielded similar results. CONCLUSIONS: The absolute value of the repeat lactate measurement had the greatest ability to predict mortality in injured patients undergoing resuscitation.