Association between lactate trajectory and 30-day mortality in patients with acute kidney injury and delirium: A retrospective study

ObjectiveTo investigate the associations of baseline serum lactate level, lactate quartiles, and lactate trajectories with 30-day mortality in critically ill adults with acute kidney injury (AKI) and delirium.MethodsData were extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Adult patients admitted to the intensive care unit (ICU) with concurrent AKI and delirium were included. Lactate levels over the first 72 hours were analyzed using group-based trajectory modeling. In parallel, baseline lactate levels were examined as a continuous variable and categorized into quartiles. The primary outcome was defined as 30-day mortality. Restricted cubic splines (RCS), multivariable Cox regression, and subgroup analyses were conducted to evaluate prognostic associations.ResultsRCS revealed a linear positive association between lactate levels and 30-day mortality. However, after adjusting for multiple confounders, baseline lactate alone was not independently associated with 30-day mortality. When categorized by quartiles, only the third quartile group was associated with higher mortality compared to the first quartile. In contrast, lactate trajectories demonstrated strong and consistent predictive value. Four distinct dynamic patterns were identified: low-stable, mildly elevated-decreasing, high-decreasing-rebound, and moderate-early rise-decline. Patients in the low-stable trajectory had the most favorable prognosis, while those with early elevation or fluctuating trends exhibited significantly higher mortality. Subgroup analyses confirmed the robustness of these associations across different comorbidities.ConclusionsDynamic lactate trajectories provide more robust prognostic information than baseline metrics, complementing the role of lactate in risk stratification and prognostic assessment for patients with AKI and delirium.