To practically determine the effect of chloride on the acid-base status, four approaches are currently used: accepted ranges of serum chloride values; chloride corrections; the serum Cl/Na ratio; and the serum sodium-chloride difference. However, these approaches are governed by different concepts. Our aim is to investigate which approach to the evaluation of the effect of chloride is the best. In this retrospective cohort study, 2529 critically ill patients who were admitted to the tertiary care unit between 2011 and 2018 were retrospectively evaluated. The effects of chloride on the acid-base status according to each evaluative approach were validated by the standard base excess and apparent strong ion difference. To compare approaches, kappa and Bland-Altman tests and a linear regression model were used. In the linear regression model, only base-excess chloride in all the chloride evaluation approaches was significantly related to the standard base excess. In the subgroup, limits of agreement between base-excess chloride and the standard base excess were the closest (bias: 0.5mmol/L). For the evaluation of the effect of chloride on the acid-base status, base-excess chloride is a better approach than accepted ranges of serum chloride values, chloride corrections and the Cl/Na ratio.

All data were fully anonymized without restriction after the ethic committee approval and ethic committee waived the requirement for informed consent. Data collecting was started on 01.01.2018 and 2529 patients who were admitted to the tertiary intensive care unit (ICU) in Acıbadem International Hospital between January 1st, 2011, and January 1st, 2018 were retrospectively evaluated.