Severe hyperlactatemia in the emergency department: clinical characteristics, etiology and mortality.

Background: Severe hyperlactatemia (lactate level ≥ 10 mmol/L) is associated with high mortality rates in critically ill patients. However, there is limited data on emergency department (ED) patients. We aimed to investigate the clinical characteristics, etiology and outcomes of patients with severe hyperlactatemia in the ED setting.

Methods: A retrospective cohort study was conducted at a tertiary care hospital in Thailand. We included adult patients with a venous lactate sample taken in the ED within one hour. We excluded patients after out-of-hospital cardiac arrest, transferred to/from another hospital or those with missing clinical data. Mortality rates were evaluated among patients with increasing degrees of lactate elevation and among patients with severe hyperlactatemia, stratified by causative etiology.

Results: We analyzed venous lactate levels in 40,047 patients, with 26,680 included in the analysis. Among these, 1.7% had severe hyperlactatemia (lactate ≥ 10 mmol/L), 10.5% moderate (4-9.99 mmol/L), 28.8% mild (2-3.99 mmol/L), and 59.0% normal levels (< 2 mmol/L). Severe hyperlactatemia was associated with high mortality rates of 29%, 37%, and 38% at 7, 28, and 60 days respectively, significant ICU admissions and mechanical ventilation rates. Patients with severe hyperlactatemia were stratified into high (> 50% mortality), moderate (21-50%), and low (< 20%) 28-day mortality risk groups. High-risk conditions included non-septic shock, traumatic injuries/burns, and neurological issues, with mortality rates of 51.1%, 61.8%, and 57.1%, respectively. In the moderate risk group, namely infection without shock showed a high prevalence, with a mortality rate of 36%. In the low-risk group, seizures and fainting were associated with lower mortality, exhibiting mortality rates of 0%.

Conclusions: Severe hyperlactatemia is associated with higher rates of ICU admission and mortality compared to other degrees of lactate elevation in a general ED population. However, mortality rates can vary considerably, depending on the underlying etiology associated with different primary diagnoses.