Increase in chloride from baseline is independently associated with mortality in critically ill children.

Purpose: To determine if there is an association between mortality and admission chloride levels and/or increases in the chloride level in critically ill children.

Methods: We performed a retrospective cohort study of all patients admitted to the paediatric intensive care unit (PICU) from January 2014 to December 2015. Patients were excluded for the following reasons: (1) age < 90 days or > 18 years, (2) admission to the cardiac intensive care unit, (3) no laboratory values upon admission to the PICU, (4) history of end-stage renal disease, (5) a disorder of chloride transport, and (6) admission for diabetic ketoacidosis. The patients were stratified on the basis of admission chloride levels (hypochloraemia, < 96 mEq/L; normochloraemia, 96-109 mEq/L; and hyperchloraemia, ≥ 110 mEq/L) and dichotomised on the basis of an increase in chloride in the first day (< 5 mEq/L, ≥ 5 mEq/L). Our primary outcome was in-hospital mortality.

Results: A total of 1935 patients [55% female, median age 6.3 years IQR (1.9-13.4)] were included. The overall mortality was 4% (n = 71) and day 2 AKI occurred in 17% (n = 333. Hypochloraemia, hyperchloraemia, and an increase in serum chloride ≥ 5 mEq/L occurred in 2%, 21%, and 12%, respectively. After adjusting for confounders, increase in chloride ≥ 5 mEq/L was associated with a 2.3 (95% CI 1.03-5.21) greater odds of mortality.

Conclusions: An increase in serum chloride level in the first day of admission is common and an independent risk factor for mortality in critically ill children. Further studies are warranted to identify how chloride disturbances contribute to mortality risk in critically ill children.