Association between serum anion gap and all-cause mortality in critically ill patients with Gastrointestinal bleeding: insights from MIMIC-IV database

Serum anion gap (AG) holds potential for clinical application in the prognostic assessment of ill patients. Yet its association with all-cause mortality in critically ill patients with gastrointestinal bleeding (GIB) remains underexplored. This cohort study analyzed data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database, 2,333 critically ill GIB patients, recording their first-time AG levels. The relationship between AG, ICU mortality, and 90-day mortality in GIB patients was analyzed using the Kaplan-Meier (KM) survival curve, and COX regression model. Restricted cubic splines and subgroup analysis were conducted to enhance the stability and reliability of the findings. A total of 2,333 patients diagnosed with GIB were included in the study. The overall ICU and 90-day mortality in the entire cohort were 9.17% and 27.73%, respectively. KM analysis revealed a significant relationship between high AG and the risk of all-cause mortality (log-rank P < 0.001). After adjusting for all confounders, the association between AG and ICU and 90-day all-cause mortality was significant (HR = 1.07, 95% CI: 1.03–1.12; HR = 1.06, 95% CI: 1.04–1.09, separately). Furthermore, we assessed the potential linear relationship between AG and all-cause mortality (P for non-linearity > 0.05). Subsequent subgroup analysis demonstrated that weight and heart failure could impact the association between the two. AG emerges as a significant biomarker, closely associated with heightened ICU and 90-day mortality in individuals suffering from GIB.