Non-linear Association Between Lactate Levels and ICU Mortality in Septic Patients: A Multi-Center Study of 13,888 Cases.

BackgroundBlood lactate is a crucial prognostic indicator in sepsis, but its non-linear relationship with mortality remains unclear. This study aimed to investigate the complex association between lactate levels and ICU mortality in septic patients.MethodsIn this multi-center retrospective study of 13,888 septic patients from the eICU database, we analyzed the association between admission lactate levels and ICU mortality using multivariate models and threshold effect analysis. Models were adjusted for demographics, comorbidities, laboratory parameters, medications, mechanical ventilation status, and APACHE IV scores.ResultsA total of 13,888 septic patients were recruited, including 1688 (12.2%) with ICU mortality. Admission lactate level was positively correlated with ICU mortality. When adjusting for potential confounders, the ICU mortality risk in patients in the highest lactate quartile (>5.2 mmol/L) increased by 133% relative to those in the lowest quartile (<2.0 mmol/L) (OR 2.33, 95% CI 1.91-2.83, P < 0.001). No significant interactions were observed in subgroups based on age, sex, BMI, APACHE IV score, acute myocardial infarction, renal replacement therapy, or vasopressor use (all P-interaction >0.05)，however, Significant interactions were observed in subgroups based on acute respiratory failure (P-interaction <0.001) and mechanical ventilation (P-interaction = 0.004).ConclusionLactate demonstrates a non-linear relationship with ICU mortality in septic patients, with 6.09 mmol/L as a critical threshold. This finding provides evidence for risk stratification and treatment decisions in sepsis management.