Relationship between acid–base status and inflammation in the critically ill

INTRODUCTION There is a complex interplay between changes in acid-base components and inflammation. This manuscript aims to explore associations between plasma cytokines and chemokines and acid-base status on admission to intensive care. METHODS We conducted a prospective cohort study in a 13-bed ICU in a tertiary-care center in Brazil. 87 unselected patients admitted to the ICU during a 2-year period were included. We measured multiple inflammatory mediators in plasma using multiplex assays and evaluated the association between mediator concentrations and acid-base variables using a variety of statistical modeling approaches, including generalized linear models, multiadaptive regression splines and principal component analysis. RESULTS We found a positive association between strong ion gap (SIG) and plasma concentrations of interleukin (IL)6, 8, 10 and tumor necrosis factor (TNF); whereas albumin was negatively associated with IL6, IL7, IL8, IL10, TNF and interferon (IFN)α. Apparent strong ion difference (SIDa) was negatively associated with IL10 and IL17. A principal component analysis including SAPS 3 indicated that the association between acid-base components and inflammatory status was largely independent of illness severity, with both increased SIG and decreased SIDa (both drivers of acidosis) associated with increased inflammation. CONCLUSION Acid-base variables (especially increased SIG, decreased albumin and decreased SIDa) on admission to ICU are associated with immunological activation. These findings should encourage new research into the effects of acid-base status on inflammation.