Clinical value of triage lactate in risk stratifying trauma patients using interval likelihood ratios.

Unlabelled: Emergency physicians face the challenge of rapidly identifying high-risk trauma patients. Lactate (LAC) is widely used as a surrogate of tissue hypoperfusion. However, clinically important values for LAC as a predictor of mortality are not well defined.

Objectives: 1. To assess the value of triage LAC in predicting mortality after trauma. 2. To compute interval likelihood ratios (LR) for LAC.

Methods: Retrospective chart review of trauma patients with a significant injury mechanism that warranted labs at an urban trauma center.

Outcome: In-hospital mortality. Data are presented as median and quartiles or percentages with 95% confidence intervals. Groups (lived vs. died) were compared with Man-Whitney-U or Fisher's-exact test. Multivariate analysis was used to measure the association of the independent variables and mortality. The interval likelihood ratios were calculated for all LAC observed values.

Results: 10,575 patients; median age: 38 [25-57]; 69% male; 76% blunt; 1.1% [n=119] mortality. LAC was statistically different between groups in univariate (2.3 [1.6,3.0] vs 2.8 [1.6,4.8], p=0.008) and multivariate analyses (odds ratio: 1.14 [1.08-1.21], p=0.0001). Interval ratios for LR- ranged from 0.6-1.0. Increasing LAC increased LR+. However, LR+ for LAC reached 5 with LAC>9mmol/L and passed 10 (moderate and conclusive increase in disease probability, respectively) with LAC>18mmol/L.

Conclusions: In a cohort of trauma patients with a wide spectrum of characteristics triage LAC was statistically able to identify patients at high risk of mortality. However, clinically meaningful contribution to decision-making occurred only at LAC>9. LAC was not useful at excluding those with a low risk of mortality.