Lactate trajectories and outcomes in critically ill patients with septic shock: a retrospective analysis of the MIMIC-IV database

BACKGROUND: Static measurements of lactate concentrations are insufficient to fully capture the metabolic dynamics that occur during disease progression. We aimed to investigate the lactate trajectories and their association with 7-day and 28-day all-cause mortality in critically ill patients with septic shock. METHODS: Critically ill patients with septic shock were obtained from the MIMIC-IV database (v3.1). Latent growth mixture models (LGMM) and smoothed curve fitting were used to investigate lactate trajectories. Multinomial logistic regression models were employed to examine the associations between the characteristics of membership identified by the least absolute shrinkage and selection operator (LASSO) regression and lactate trajectories. Cox regression models were used to investigate the association between lactate trajectories and all-cause mortality. RESULTS: A total of 2,211 patients with 18,518 lactate measurements collected over the three days following ICU admission were included. The 7-day and 28-day all-cause mortality rates were 26.5% and 35.5%, respectively. Three distinct lactate trajectories were identified: Class 1, “Moderate level with improvement”; Class 2, “High level with improvement”; and Class 3, “High level with deterioration”. In addition to elevated baseline lactate levels, vasopressor use at ICU admission was independently associated with a significantly higher probability of belonging to Class 3. After adjustment for confounding variables, patients in Classes 2–3 exhibited significantly higher 7-day and 28-day mortality risks compared to those in Class 1 (all adjusted HRs (95% CIs) > 1, P < 0.001; all P for trend < 0.001). Integrating the SOFA score with lactate trajectories could significantly enhance the accuracy of the SOFA score in evaluating patient prognosis. The sensitivity analysis confirmed the lactate trajectories and their association with mortality. CONCLUSIONS: Significant heterogeneity in lactate trajectories was observed over the three days following ICU admission among critically ill patients with septic shock. Lactate trajectories were closely associated with patient outcomes and could potentially serve as a dynamic metabolic marker for actionable risk stratification in this population.