Association between sodium level trajectories and clinical prognosis in patients with sepsis: A longitudinal retrospective cohort study

ObjectiveSepsis treatment remains challenging in ICU due to patient heterogeneity. Although sodium imbalance is common and associated with poor outcomes, its longitudinal dynamics and complexity have been overlooked. This study aimed to identify sodium trajectories in ICU patients with sepsis and evaluate their prognostic value.MethodsThis retrospective study included ICU patients with sepsis from the Medical Information Mart for Intensive Care IV v3.0 database. Time-series sodium measurements were extracted for the first 8 days of ICU stay. Latent Class Mixed Model was used to identify sodium trajectory patterns. The primary outcome was 28-day mortality, and the secondary outcome was 90-day mortality. Kaplan-Meier, cox regression, and logistic regression analyses were employed to examine associations between trajectory classes and outcomes. Further SHAP analysis quantified the contribution of individual features to mortality across the different classes. Subgroup analyses assessed robustness and effect modification.ResultsA total of 9697 patients were included and divided into four trajectory groups: "U-shaped increase"; "Low-level stable"; "High-level stable"; and "Inverted U-shaped decrease". Class 1 exhibited the highest mortality risk, followed by Class 4, with adjusted hazard ratios (HRs) of 1.55 (95% CI: 1.30-1.85; <i>p</i> < 0.001) and 1.44 (95% CI: 1.18-1.74; <i>p</i> < 0.001), respectively. The death risk of Class 1 is primarily driven by indicators of acute physiologic disturbances. For class 4, the short- and long-term mortality risks were mainly influenced by comorbidities and coagulopathy. Subgroup analysis showed that the risk of death was more significant in class 1, particularly in patients with Simplified Acute Physiology Score < 35 (HR = 3.47, 95%CI:2.37-5.07, (<i>p</i> < 0.001)).ConclusionsThis study identified four distinct sodium level trajectory sub-phenotypes in ICU patients with sepsis and examined the risk factors associated with mortality. These findings provided a basis for risk stratification of sepsis patients and may inform personalized critical care strategies.