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

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.

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

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

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.

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.

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.