Non-linear association between anion gap and 28-day mortality in critically ill patients with COVID-19: a cohort study from MIMIC IV database.

Background: There is currently little evidence linking serum anion gap (AG) to mortality within 28 days in patients with coronavirus disease 2019 (COVID-19) in intensive care units. The purpose of this study is to examine how serum AG affects the 28-day mortality in COVID-19 patients who are in critical condition. Methods: We included 811 individuals with a COVID-19 diagnosis who were hospitalized in intensive care units (ICU) in the Medical Information Mart for Intensive Care IV (MIMIC IV) 3.0 database participated in this retrospective cohort research. All individuals' vital signs, laboratory results, and comorbidities were gathered to examine the relationship between 28-day mortality and AG levels. Results: The research comprised 811 patients with COVID-19 in the ICU. The cohort comprised of 59.6% to 40.4% male to female ratio, and the mean age was 64.1 years. The 28-day mortality rate was 27.4% overall. In unadjusted analysis, a higher admission AG was substantially associated with an increased mortality risk [hazard ratio (HR) =1.12; 95% confidence interval (CI): 1.09-1.15; P<0.001]. The association remained significant after controlling for potential covariates (adjusted HR =1.07; 95% CI: 1.04-1.11; P<0.001). The highest T3 group had a substantially higher risk of 28-day death than the lowest T1 group when AG was categorized into tertiles (Model 3: HR =1.48, 95% CI: 1.01-2.17, P=0.042). Results from subgroup analysis were consistent across groups. Conclusions: In critically ill patients with COVID-19, a higher admission AG was independently associated with an increased 28-day mortality rate.