Association between fluctuations in serum chloride levels and 30-day mortality among critically ill patients: A retrospective analysis

Abstract

Background: This study investigated the associations of fluctuations in serum chloride (Cl-) levels with 30-day mortality after intensive care unit (ICU) admission among critically ill patients. Methods: We retrospectively analyzed the medical records of adult patients (≥18 years old) admitted to the ICU between January 2012 and December 2017. Positive and negative fluctuations in Cl- were defined as the differences between the Cl- upon ICU admission (baseline Cl-) and the maximum and minimum Cl- levels, respectively, measured within 72 h after ICU admission. Results: The final analysis included 18,825 adult patients. In multivariable Cox regression analyses, the risk of 30-day mortality increased by 8% per 1-mmol L-1 positive fluctuation in Cl- within 72 h (hazard ratio = 1.08, 95% confidence interval: 1.04-1.11, P < 0.001). In subgroup analyses, a positive fluctuation in Cl- was associated with increased 30-day mortality among patients with a severe positive cumulative fluid balance (FB, > 10%), normochloremia (97-110 mmol L-1) or hyperchloremia (> 110 mmol L-1) upon ICU admission. Furthermore, a negative fluctuation in the Cl- level during the first 72 h of an ICU stay was associated with a negative cumulative FB (< 0%) or hypochloremia (< 97 mmol L-1) upon ICU admission. Conclusions: A fluctuation in the Cl- level during the first 72 h of an ICU stay was found to associate independently with increased 30-day mortality among critically ill adult patients. However, the nature of this association differed according to the cumulative FB status or dyschloremia status upon ICU admission.