Association of continuous anion gap testing with mortality in critically ill patients receiving continuous renal replacement therapy

Tang Yi; Chen Qianyi; Liu Liming; Chen Weixiang

doi:10.13498/j.cnki.chin.j.ecc.2025.04.07

Abstract：Objective To investigate the correlation between continuous anion gap(AG)detection and 28-day mortality in critically ill patients undergoing continuous renal replacement therapy(CRRT).Methods A retrospective study was conducted on 143 critically ill patients with acute kidney injury who underwent CRRT in our intensive care unit from March 2021 to September 2024.According to the 28-day survival outcome,all patients were divided into death group and survival group.AG levels were monitored before CRRT(preCRRT)and 24 h after CRRT(postCRRT 24 h),and △AG(preCRRT-postCRRT 24 h AG)changes were recorded.Results According to the 28-day overall survival data,all participants were divided into a survival group(n=68)and a death group(n=75).The median follow-up time from ICU admission to discharge or death was 18.60(8.53,38.16)days.The preCRRT or postCRRT 24 h AG levels in death group was significantly higher than that in survival group(P<0.05),and △AG in death group was significantly lower than that in survival group(P<0.05).In restricted cubic spline analysis,preCRRT AG,postCRRT 24 h AG,and △AG were linearly correlated with 28 d mortality risk.After adjusting for other confounding factors,multivariate COX regression analysis showed that preCRRT AG,postCRRT 24 h AG and △AG were independent predictors of 28 d mortality risk in critically ill patients receiving CRRT(P<0.05).ROC curve analysis showed that preCRRT AG and postCRRT 24 h AG had predictive value of 0.886(95%CI:0.847-0.927)and 0.883(95%CI:0.844-0.922)for 28 d mortality risk,which was better than sequential orgen failure assessment score[0.656(95%CI:0.593-0.719)]and estimated glomerular filtration rate[0.591(95%CI:0.525-0.657)].Conclusion Higher preCRRT or postCRRT 24 h AG levels and smaller△AG were all significantly associated with an increased risk of death at 28 days in critically ill patients receiving CRRT.