The effects of the chloride:sodium ratio on acid-base statusand mortality in septic patients

Calculation of the chloride:sodium (Cl^-:Na⁺) ratio is proposed to enable a quick evaluation of the effect of Cl^- and Na⁺ on the acid-base balance in critically ill patients. In the present study, the relationship of the Cl^-:Na⁺ ratio of septic patients with acid-base status and ICU mortality were investigated.

In our two-center study, 434 patients who were diagnosed with sepsis were included. The patients were divided into three groups: low (<0.75), normal (≥0.75, <0.80), and high (≥0.80) Cl^-:Na⁺ ratio groups. Patients' demographic data, blood gas values, length of ICU stay, and ICU mortality were recorded.

In the low and high groups, ICU mortality was significantly higher than in the normal group (29.3%, 37.1%) (P = 0.005). There was a negative correlation between the Cl:Na⁺ ratio and each of HCO₃^-, standard base excess, and PaCO₂ (r² = 0.21, r² = 0.19, and r² = 0.17) (P < 0.001 for each). In the multivariate analysis, the ICU mortality was increased 2.6-fold (1.2-5.8) by low Cl^-:Na⁺ ratio (P = 0.019).

The Cl^-:Na⁺ ratio is a useful parameter for showing the relationship between Cl^- and Na⁺ and their impact on acid-base status. Low Cl^-:Na⁺ ratio at ICU admission can be used as a prognostic indicator for increased ICU mortality in septic patients.