Associations of continuous anionic gap detection with the mortality in critically ill patients receiving renal replacement therapy

PURPOSE: To investigate the associations of anion gap (AG) levels before and 1-day after hemodialysis as well as anion gap changes with the mortality in critically ill patients receiving renal replacement therapy (RRT). METHODS: Totally, 637 patients from MIMIC-III were included in this cohort study. The associations between AG (T0), AG (T1), or ∆AG [AG (T0) − AG (T1)], and the risk of 30-day or 1-year mortality were examined by Cox restricted cubic spline regression models. Univariate and multivariate Cox proportional-hazards model was applied to assess the associations between AG (T0), AG (T1), ∆AG with 30-day and 1-year mortality, respectively. RESULTS: The median follow-up time was 18.60 (8.53, 38.16) days and 263 (41.3%) patients were survived. There was a linear relationship between AG (T0), AG (T1) or ∆AG and the risk of 30-day or 1-year mortality, respectively. The risk of 30-day mortality was higher in AG (T0) > 21 group (HR = 1.723, 95% CI 1.263–2.350), and AG (T1) > 22.3 group (HR = 2.011, 95% CI 1.417–2.853), while lower in AG > 0 group (HR = 0.664, 95% CI 0.486–0.907). The risk of 1-year mortality was increased in AG (T0) > 21 group (HR = 1.666, 95% CI 1.310–2.119), and AG (T1) > 22.3 group (HR = 1.546, 95% CI 1.159–2.064), while decreased in AG > 0 group (HR = 0.765, 95% CI 0.596–0.981). Patients with AG (T0) ≤ 21 had higher 30-day and 1-year survival probability than those with AG (T0) > 21. CONCLUSION: AG before and after dialysis as well as the changes of AG were important factors associated with the risk of 30-day and 1-year mortality in critically ill patients receiving RRT. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11255-023-03583-4.