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

BackgroundThis 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.MethodsWe retrospectively analyzed the medical records of adult patients (18years 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 72h after ICU admission.ResultsThe final analysis included 18,825 adult patients. In multivariable Cox regression analyses, the risk of 30-day mortality increased by 8% per 1-mmolL(-1) positive fluctuation in Cl- within 72h (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 (97-110mmolL(-1)) or hyperchloremia (>110mmolL(-1)) upon ICU admission. Furthermore, a negative fluctuation in the Cl- level during the first 72h of an ICU stay was associated with a negative cumulative FB (<0%) or hypochloremia (<97mmolL(-1)) upon ICU admission.ConclusionsA fluctuation in the Cl- level during the first 72h 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.