Association between the anion-gap and 28-day mortality in critically ill adult patients with sepsis: A retrospective cohort study

Metabolic acidosis is usually associated with the severity of the condition of patients with sepsis or septic shock. Serum anion gap (AG) is one of the indicators of response metabolism. This study was performed to investigate whether the initial serum AG is associated with the 28-day mortality in critically ill adult patients with sepsis. This retrospective cohort study, a total of 15,047 patients with confirmed Sepsis disease from 2008 to 2019 from the Medical Information Mart for Intensive Care IV (MIMIC-IV) v1.0 database. The MIMIC-IV database is a comprehensive, de-identified clinical dataset originating from the Beth Israel Deaconess Medical Center in Boston, it includes extensive data on intensive care unit (ICU) patients, such as vital signs, lab results, and medication orders, spanning multiple years, accessible to researchers through an application process. AG can be obtained by direct extraction in the MIMIC-IV database (itemid = 50,868 from the laboratory events table of mimic_hosp), inclusion of AG values for the first test on first day of ICU admission. The patients were grouped into quartiles according to the AG interquartile range. The primary outcome was the 28-day mortality. Multiple logistic regression analysis was used to calculate the odds ratio (OR), while accounting for potential confounders, and the robustness of the results were evaluated in subgroup analyses. Among the 15,047 patients included in this study, the average age was 65.9 ± 16.0 years, 42.5% were female, 66.1% were Caucasian, and the 28-day mortality rate was 17.9% (2686/15,047). Multiple logistic regression analysis revealed the 28-day mortality in every increase of AG (per SD mEq/L), there is an associated 1.2 times (OR 1.2, 95% CI 1.12-1.29, P < .001) increase. Increased 28-day mortality (OR 1.53, 95% confidence interval 1.29-1.81, P < .001) in the group with the AG (15-18 mEq/L), and (OR 1.69, 95% confidence interval 1.4-2.04, P < .001) in the group with the highest AG (≥18 mEq/L), AG (<12 mEq/L) as a reference group, in the fully adjusted model. In adult patients with sepsis, the early AG at the time of ICU admission is an independent risk factor for prognosis.