Association of serum chloride level alterations with in-hospital mortality

Abstract Background We aimed to assess the association between alterations in serum chloride levels during hospitalisation and mortality. Methods We reviewed all adult patients admitted to our hospital from the year 2009 to 2013, who had at least two serum chloride measurements during hospitalisation. The serum chloride change during hospitalisation, defined as the absolute difference between the highest and lowest serum chloride levels, was categorised into seven groups; 0–2, 3–4, 5–6, 7–8, 9–10, 11–12 and ≥13 mEq/L. Multivariable logistic regression was performed to assess the independent association between serum chloride change and in-hospital mortality, using the serum chloride change of 0–2 mEq/L as the reference group. Results A total of 57 880 patients, with median serum chloride change of 5 (IQR 3–9) mEq/L, were studied. The in-hospital mortality was progressively increased with larger chloride change, from 0.6% in group of 0–2 mEq/L to 5.9% in group of ≥13 mEq/L (p<0.001). In adjusted analysis, serum chloride change of ≥7 mEq/L was significantly associated with increased in-hospital mortality. For upward trend, serum chloride change of ≥3 mEq/L was significantly associated with increased in-hospital mortality, whereas, for downward trend, serum chloride change was not consistently associated with in-hospital mortality. Conclusion Alterations in serum chloride during hospitalisation were associated with increased hospital mortality. The association was more prominent with upward than downward trend of serum chloride.