A. Jordan1, W. Terzian1, T. R. Wojda3, M. S. Cohen2, J. Luster4, J. Seoane4, P. Salen2, H. Stankewicz2, E. McCarthy3, S. P. Stawicki1,3 1St. Luke’s University Health Network,Department Of Surgery,Bethlehem, PA, USA 2St. Luke’s University Health Network,Department Of Emergency Medicine,Bethlehem, PA, USA 3St. Luke’s University Health Network,Department Of Research & Innovation,Bethlehem, PA, USA 4Temple University,St. Luke’s University Hospital Campus,Bethlehem, PA, USA
Introduction: Mortality prediction in trauma continues to be challenging, with unexpected deaths continuing despite better understanding of pathophysiology and clinical management of trauma-related shock. Several laboratory variables have been evaluated for their ability to quantitate mortality risk in injured patients. Despite individual drawbacks, popular indicators of physiologic stress are serum bicarbonate (SB), anion gap (AG), base deficit (BD), and lactate. The aim of this study was to compare the utility and mortaliy prediction for each of these variables in a large, single institution trauma patient sample.
Methods: After IRB approval, we queried our Level I Trauma Center registry records for patient sex, age, ISS, GCS, mortality, and initial (trauma bay) laboratory assessments (comprehensive metabolic panel + subcomponents, arterial + venous blood gases). Main outcome variable was 30-day mortality. Analyses included the examination of stratified AG (≤3, 6, 9, etc), BD (≥16, 12, 8, etc), SB (≤10, 14, 18, etc) and lactate (≤1, 2, 3, etc) versus 30-day mortality (adjusted for sex, age, and ISS). Additional comparisons evaluated the ability of each of the above variables to predict mortality using receiver operating characteristic (ROC) curves (DeLong method). Data are reported as mean±standard deviation (SD) or median with interquartile range (IQR). AUC values are reported as area±standard error (SE). Statistical significance was set at α<0.01.
Results: The study sample included 2,811 patients (70% male; median age 44 yrs with IQR 26-58 yrs, median ISS 9 with IQR 4-16, and 5% mortality). Available laboratory values included: mean serum lactate 2.83±2.51 (n=371), mean BD 1.27±5.01 (n=1,167), mean SB 24.8±5.29 (n=2,165), and AG 11.2±6.80 (n=2,128). Mortality increased with escalating physiologic stress, as reflected by each indicator corrected for age, sex, and ISS (Fig 1; all p<0.001). Overall, serum lactate was the best predictor for mortality (AUC, 0.75±0.04SE) followed by BD (0.724±0.03), SB (0.679±0.03) and AG (0.661±0.03). Combinations of the above parameters did not improve mortality prediction.
Conclusion: Although all of the variables examined in this study offer predictive value for trauma-related mortality, initial serum lactate and BD are superior to serum bicarbonate or AG. Initial serum lactates ≥3 are associated with doubling of mortality, while lactates ≥7 carry more than quadruple baseline mortality. For BD, mortality increases from <5% for BD <4 to >40% for BD >16. In the absence of lactate or BD assessments, serum bicarbonate and AG may be helpful in crude mortality risk stratification.
