Association between sodium–chloride difference at ICU admission and 30-day mortality: a retrospective cohort study of critically ill adults
Year: 2025
Type: article
Study design: Observational Study
Abstract: BACKGROUND: The difference between serum sodium and chloride concentrations (SCD) is a simple parameter reflecting the interplay between major extracellular electrolytes. We investigated whether SCD assessed upon intensive care unit (ICU) admission holds predictive value for short-term outcomes in critically ill adults. METHODS: We retrospectively analyzed 1,726 consecutive patients admitted to a mixed (medical-surgical) ICU (median age 67 years; 70.7% male). The relationship between admission SCD and 30-day mortality was first assessed using restricted cubic spline (RCS) regression to explore non-linearity. To define potential thresholds, cut-off values were evaluated using ROC analysis with the Youden index. Cox proportional hazards models were then applied. Internal validation was performed using bootstrap resampling with 1,000 iterations. RESULTS: RCS analysis revealed a non-linear association between SCD and mortality, with risk increasing markedly at lower values. Both spline modeling and receiver operating characteristic (ROC) analysis consistently indicated 30 mmol/L as the threshold of prognostic significance. Patients with SCD < 30 mmol/L (n = 343; 19.9%) had significantly higher 30-day mortality compared with those with SCD ≥ 30 mmol/L (55.7% vs. 44.3%, p < 0.001). In Cox regression, SCD < 30 mmol/L was associated with increased mortality (unadjusted HR 1.41, 95% CI 1.20-1.66; p < 0.001). This relationship remained robust after adjustment for age, SOFA score, lactate, and major comorbidities (adjusted HR 1.48, 95% CI 1.24-1.77; p < 0.001) and was confirmed by bootstrap validation. CONCLUSIONS: Low SCD at ICU admission was independently associated with higher 30-day mortality. This routinely available parameter, reflecting the sodium-chloride interplay, may support early risk stratification in this group of patients.
Source: BMC Anesthesiology
Authors: Rafał Świstek, Jakub Konieczyński, Jakub Droś, Patryk Kasongo, Wojciech Szpunar, Tomasz Lonc, Anna Kwinta, Rafał Depukat, Elżbieta Glück, Joanna Jóźwik, Marcin Zuwała, Patrycja Machno, Paulina Górnicka, Jan Potoniec, Justyna Chomej, Emilia Torbus, Aleksandra Kowalska, Alicja Hojda, Ewa Imielska, Alicja Warecka, Kacper Melka, Aleksandra Sielska, Gabriela Piotrowska, Alicja Włodarczyk, Błażej Mioduszewski, Anna Górowska, Tomasz Drygalski, Michał Terlecki
Institution: Jagiellonian University
Language: English
Subfield: Epidemiology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,190
OpenAlex ID: W4416122252