Predictive value of strong ion gap in the prognosis of critically ill patients with acute kidney injury
Objective To explore the predictive value of strong ion gap(SIG)in the short-term and long-term prognosis of critically ill patients with acute kidney injury(AKI).Methods The clinical data of adult patients with AKI in the intensive care unit were obtained from the United States Intensive Care Database(MIMIC-Ⅳ,version v2.0;2008-2019).According to the 90 d prognosis,the patients were divided into survival group and death group.Restricted cubic spline(RCS)was used to analyze the relationship between SIG and 90 d all-cause mortality to determine the optimal cut-off value of SIG,according to the value of SIG,the patients were divided into low SIG group and high SIG group.The Kaplan-Meier method was used to compare the 30 and 90 d cumulative survival rates of the low SIG group and the high SIG group;multivariate Cox regression model was used to analyze the association of SIG with 30 and 90 d all-cause mortality.Su-bgroup analysis to further investigate the possible interaction between SIG levels and 90 d all-cause mortality.Results A total of 9 118 critically ill patients with AKI were included,including 6 058 cases in survival group and 3 060 cases in death group according to the 90 d prognosis.The 90 d all-cause mortality was 33.56%.There were significant differences in age,sex,sequential organ failure score,charlson combined index,anion gap,albumin,blood phosphate,SIG,WBC,Hb,red blood cell distribution width,PLT,creatinine,blood urea nitrogen,PT,PaO2,total blood calcium,blood magnesium,norepinephrine,mechanical ventilation,continuous renal replacement therapy,hypertension,atrial fibrillation,liver cirrhosis,acute pancreatitis,myocardial infarction,cardiac arrest,sepsis,and hospitalization time between the survival and death groups(all P<0.05).RCS showed that there was a non-linear relationship between SIG and the risk of 90 d all-cause mortality in patients with AKI(P=0.010).According to the optimal SIG cut-off value(4.87 mmol/L),the patients were divided into low SIG group(<4.87 mmol/L,n=4 592)and high SIG group(≥ 4.87 mmol/L,n=4 526).The 30 and 90 d all-cause mortality in the low SIG group were 19.60%and 26.26%,and in the high SIG group were 33.65%and 40.96%,respectively(both P<0.01).Kaplan-Meier survival curve showed that compared with the low SIG group,the high SIG group had lower 30 and 90 d cumulative survival rates(both P<0.01).Multivariate Cox regression analysis showed that elevated SIG was an independent risk factor for 30 and 90 d all-cause mortality in critically ill patients with AKI(both P<0.01).Subgroup analysis showed that,except for age and hypertension,most subgroup stratification factors had no significant impact on the relationship between SIG levels and 90 d all-cause mortality.Conclusion Elevated SIG(≥ 4.87 mmol/L)is an independent risk factor for all-cause mortality in critically ill patients with AKI.SIG has a certain predictive value for the prognosis of critically ill patients with AKI,and helps clinicians to identify the population with poor prognosis early.