Assessing lactate concentration as a predictor of 28-day in-hospital mortality in the presence of ethanol: A retrospective study of emergency department patients.

Background: Presence of ethanol (EtOH) may alter the relationship between blood lactate concentrations and mortality. This study compares lactate-associated mortality risk in the presence and absence of EtOH.

Methods: We performed a retrospective cohort study including all patients, age >17 years, presenting from January 2012-December 2018, to an urban, academic emergency department, with a clinically measured lactate. Data were electronically abstracted from the medical record. The primary outcome was 28-day in-hospital mortality. Patients were grouped by EtOH test results as follows: 1) present (any EtOH detected), 2) absent (EtOH concentration measured and not detected), or 3) not ordered. Marginal analysis was used to calculated probability of mortality for fixed values of lactate and model covariates.

Results: Of 40,956 adult emergency department patients with measured lactate, we excluded 768 (1.89%) for lactate >10.0 mmol/L, leaving 40,240 for analysis: 4,066 (10.1%) EtOH present, 10,819 (26.9%) EtOH absent, 25,355 (63%) EtOH not ordered. Of these, 1790 (4.4%) had 28-day in-hospital mortality. Marginal probability of mortality calculated for specific lactate values found less risk for EtOH Present patients versus EtOH absent patients at lactate 0.0 mmol/L (0.8% [95%CI: 0.5-1.2%] vs 3.2% [2.8-3.6%]), 2.0 mmol/L (1.5% [1.1-1.9%] vs 4.0% [3.7-4.3%]), 4.0 mmol/L (2.6% [2.2-3.1%] vs 5.0% [4.6-5.4%]), until 6.0 mmol/L (4.5% [3.7-5.4%] vs 6.2% [5.4-7.0%]).

Conclusion: EtOH presence significantly alters lactate-associated mortality risk when lactate <6.0 mmol/L. Emergency department clinicians should interpret these lactate values with caution and consider other data for risk stratification when EtOH is present.