Association Between Lactate and ICU-Acquired Infection in Critically Ill Patients With Sepsis: A Retrospective Study Using the MIMIC-IV Database.

Sepsis is a leading cause of Intensive Care Unit (ICU) mortality, often complicated by secondary infections due to sepsis-induced immunosuppression. The ICU-acquired infection (IAI) is of particular concern in severe cases, as it heightens the risk of progression to chronic critical illness (CCI). Given the scarcity of established biomarkers for IAI, this study aimed to evaluate the potential association of early blood lactate levels, a recognised prognostic marker in sepsis, with the occurrence of this complication. We conducted a retrospective analysis of data from the Medical Information Mart for Intensive Care (MIMIC)-IV database (v3.0), enrolling 17,209 patients. The cohort had a median age of 67 years (IQR, 56-77) and a median admission lactate level of 2.6 mmol/L (IQR, 1.6-4.8). Our analysis revealed a linear dose-response relationship between admission lactate levels and IAI risk. After multivariable adjustment, hyperlactatemia (> 6 mmol/L, i.e., the group with the highest lactate levels, Q5) remained independently associated with increased odds of IAI (OR = 1.36; 95% CI, 1.08-1.70). Notably, while elevated lactate predicted higher 28-day ICU mortality in patients without IAI, this relationship was not maintained in the IAI cohort following multivariable adjustment.