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

PurposeTo 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).MethodsTotally, 637 patients from MIMIC-III were included in this cohort study. The associations between AG (T0), AG (T1), or increment 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), increment AG with 30-day and 1-year mortality, respectively.ResultsThe 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 increment 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.ConclusionAG 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.