Incidence,Outcomes And Risk Factors Of Acute Kidney Injury In Chinease Critical Patients

ObjectiveAcute kidney injury(AKI)is one of the common clinical complications in critical patients which is associated with extended length of stay,excess costs and increased mortality.Most of the current epidemiology studies were from developed countries,muti-center data were less in developing countries.The aim of the study was to clarify the epidemiology of acute kidney injury in the Chinese critical patients,including incidence,clinical characteristics,outcomes and risk factors,and provide reliable evidence for clinical status and disease burden of acute kidney injury among the critical patients.MethodsPatients’ hospitalization data and serum creatinine data were collected from nine regional central hospitals from south,north and central China in 2013.We obtained patient-level data from the hospital electronic medical record system database and the serum creatinine test database,including those hospitalizations who were admitted to the intensive care units during hospitalization.Excluding those patients whose age were less than 15 or more than 100,CKD 4-5 stage,receiving maintenance dialysis or renal transplantation,and those who had zero or one serum creatinine test within any 7-day window during their first 30 days of hospitalization.For patients with multiple hospitalizations,we included only the first hospitalization in the analysis set.We selected the AKI patients who met the criteria as follows:1.Diagnosed with AKI when admitted to hospital.2.Patients suffered from AKI during their hospitalization,including an increase in SCr by 0.3mg/dl within 48 hours or a 50%increase in SCr from the baseline within 7 days according to the KDIGO criteria.To screen the patients with AKI in the analysis set,the SCr data during hospitalization were sorted in increasing order according to the test time.At any time point t,a baseline SCr was dynamically defined as the mean of SCr levels within the 7 days before t,and each of the available SCr data within 7 days after t was compared with this baseline.The earliest day that the SCr change met the KDIGO criteria was defined as the date of AKI onset.Trained nephrologists also manually reviewed the medical records of the patients with AKI and filled in the cases of the registration form,such as demographic characteristic,admission and discharge data,length of stay,comorbidities,extra-renal organ failure,in-hospital outcomes and total costs.The laboratory data included patients’ SCr values and test time.The information of the non-AKI group were obtained from the database of all hospitals by professional statisticians.We calculated the incidence of AKI in the critically ill hospitalized patients,and analysed the prognosis with the related risk factors.Statistical:normal continuous variables were displayed as mean ± standard deviation and compared using student’s t-test,otherwise were displayed as median(P25,P75)and compared using nonparametric Wilcoxon rank sum test.Categorical variables were expressed as constituent ratio or percentage and compared with chi-square test.Univariate and multivariate logistic regression analysis were used to establish the prediction models with AKI and the prognosis,P<0.05 in the univariate analysis were candidated for the multivariable logistic analysis.The odds ratio(OR)and confidence interval(Cl)of 95%were expressed,P＜0.05 was considered statistically significant.All the data were input by Epidata software(version2.0,Epidata Association,Odense,Denmark).All statistical analyses were performed using Empower Stats and R packages.ResultsOf 30761 critical hospitalizations in the study cohort,27029 had at least two SCr test during hospitalization.A total of 14305 critical patients met our inclusion criteria.The cases of AKI group were 4298,so the incidence of AKI was 30.04%,AKI cases for stage 1,stage 2,and stage 3 were 2240(52.1%),845(19.7%),and 1213(28.2%),the incidence for each stage was 15.7%,5.9%,8.5%,respectively.The average of age in the AKI group was(57.9± 17.2)years old.The proportion of AKI patients aged 15 to 39 group,40 to 59 group,60 to 79 group,80 to 99 group were 15%(646/4298),35.2%(1511/4298),39.3%(1690/4298)and 10.5%(451/4298),respectively.Among them the elderly patients(＞60 years)accounted for 49.8%(2141/4298).The male and female patients were 2671 and 1627,respectively,the ratio of male and female was 1.64:1.The average of the length of stay was 19(11,29)days and the average daily costs was 4673(3315,6710)yuan,which were higher than the non-AKI group(all P<0.001).The three clinical settings with the highest incidence of AKI were CKD(68.8%),shock(61.7%),and sepsis(55.4%).Among the preexisting CKD patients,compared with the non-AKI group,the AKI group had more daily cost and longer length of stay,as well as the proportion of organ failure and mortality(P＜0.001).Multivariate logistic regression analysis showed that male(OR=1.15,95%CI=1.05-1.25,P=0’002),age(compared with the 15-39 group)40-59 group(OR＝1.37,95%CI=1.21-1.55,P<0.001),60-79 group(OR＝1.72,95%CI=1.51-1.96,P<0.01),80-99 group(OR＝2.44,95%CI=2.02-2.95,P＜0.001),renal disease(OR=2.32,95%CI=1.58-3.42,P<0.001),urinary tract obstruction(OR=2.09,95%Cl＝1.29-3.40,P=0.003),pre-existing CKD(OR=5.65,95%CI＝4.90-6.52,P＜0.001),pregnancy induced hypertension(OR=4.77,95%CI= 2.17-10.48,P＜0.001),shock(OR＝3.03,95%CI=2.52-3.63,P＜0.OO1),sepsis(OR=2.30,95%CI=1.75-3.02,P<0.001),cardiac-surgery(OR=7.23,95%CI=6.27-8.35,P<0.001),interventional surgery(OR=1.13,95%CI＝1.01-1.28,P＝0.036),and extra-renal organ failure(OR=9.09,95%CI＝8.15-10.13,P<0.001)were the independent risk factors for AKI in the critical patients.The in-hospital mortality of critical patients was 2.6%in the non-AKI group and 16.7%in the AKI group.The HR(95%confidence interval)of in-hospital death was 4.95(95%CI=4.29-5.72,P＜0.001).We set the death of critically ill patients as dependent variable,AKI stage as the risk factor,the Cox regression analysis showed that the HRs for the AKI stages were 2.61,5.81,8.34 for stage 1,2,3,respectively(all P ＜0.001).The top five clinical settings with the highest mortality in the critical AKI patients were respiratory failure(64.5%),nervous system failure(51.8%),pneumonia(42.5%),hepatic failure(31.1%)and CKD(30.40%).The mortality of the AKI patients aged 15 to 39 group,40 to 59 group,60 to 79 group,80 to 99 group were 12.6%(83/646),9.7%(146/1511),18.5%(313/1690)and 38.6%(174/451)respectively.The renal non-recovery rate was 58.80%(380/646),54.00%(816/1511),59.60%(1008/1690),71.2%(321/451)for each age group(P＜0.001 for all).The cases of the critical AKI patients which combined none,one,two,three or more extra-renal failure organs were 1784,1219,714 and 581.In addition,the corresponding in-hospital mortality were 4.8%(85/1 784),16.0%(195/1219),31.1%(222/714)and 36.8%(214/581),respectively(P<0.05 for all).On the other hand,the cases of the critical AKI patients whose renal function did not recovery on discharge were 890,708,497and 430,the corresponding renal non-recovery rate were 49.9%(890/1784),58.1%(708/1219),69.6%(497/714)and 74.0%(430/581)(P<0.05 for all).As the number of extra-renal failure organs increased,the mortality and renal non-recovery rate of the critical AKI patients increased as well.The mortality for the renal replacement therapy group in the AKI patients was 32.1%,and the rate of renal non-recovery was 100%,while for the conservative treatment group,the mortality and renal function unrecovered rate was 15.4%and 55.4%.Either for the mortality rate or the renal function non-recovery rate,the renal replacement therapy group was significantly higher than the conservative treatment group,both of the differences were statistically significant(all P ＜0.001).And the HRs for the death of the patients combined one,two,three or more extra-renal failure organs were HR=3.16(95%CI=2.45-4.08,P<0.001),HR＝6.31(95%CI=4.90-8.11,P0.001),HR=7.73(95%CI＝6.01-9.95,P<0.001)as compared with those patients without organ failure.Multivariate cox regression analysis demonstrated that the independent risk factors for AKI were age(compared with the group less than 40)40-59 group(HR=0.87,95%Cl=00.66-1.15,P=0.336),60-79 group(HR=1.42,95%CI =1.10-1.85,P= 0.007),80-99group(HR＝1.61,95%CI= 1.20-2.17,P=0.002),extra-renal organ failure(HR＝3.14,95%CI＝2.48-3.98,P<0.001),acute myocardial infarction(HR=1.47,95%CI ＝1.03-2.01,P=0.036),stroke(HR＝1.28,95%CI =1.06-1.55,P＝0.010),shock(HR ＝2.14,95%CI= 1.78-2.57,P<0.001),AKI non-recovery(HR＝3.71,95%CI = 3.01-4.57,P＜0.001).In addition,AKI stage 2(HR=1.16,95%CI=1.04·1.30,P＝0.006),stage 3(HR=1.40,95%CI=1.28-1.54,P＜0.001)(stage 1 as the reference),extra-renal organ failure(HR＝1.10,95%CI＝ 1.00-1.21,P=0.042),acute myocardial infarction(HR＝2.00,95%CI=1.63-2.39,P<0.001),PIH(HR=1.84,95%CI＝1.03-3.03,P＝0.040),rheumatic disease(HR=1.35,95%CI= 1.07-1.70,P= 0.012),shock(HR＝1.53,95%CI=1.35-1.72,P＜0.001),stroke(HR=1.23,95%CI=1.28-1.54,P<0.001)and CKD(HR＝1.30,95%CI＝1.18-1.44,P<0.001))were the independent risk factors for the renal outcomes of critical AKI patients.Among the 4298 AKI critical patients whose serum creatinine change met the KDIGO criteria during hospitalization,only 5.4%of them were diagnosed as AKI or ARF or AKD on discharge or incharge.About 4064 critical AKI patients were missed diagnosis.While these missed AKI patients were older,had a longer hospital stay,spent more costs and got higher Charson Comorbidity Index,as well as mortality(P<0.001).ConclusionsAKI was a common complication in critical patients and was associated with high mortality and poor outcomes.Elderly,male,renal disease,urinary tract obstruction,CKD,pregnancy-induced hypertension,shock,sepsis,extra-renal organ failure,cardiac surgery,interventional surgery were the independent risk factors for AKI in critically ill hospitalized patients.Compared with non-AKI patients,length of stay,daily costs and in-hospital mortality were significantly increased in AKI patients.The mortality was highest in the AKI patients who with respiratory failure,followed by nervous system failure and pulmonary infection,liver failure and CKD.Elderly,associated with extra-renal organ failure,acute myocardial infarction,stroke,shock,and AKI non-recovery were the independent risk factors for death in critical AKI patients.The HRs for death increased with the older age,the severity of AKI and the number of extra-renal failure organs.AKI stage,extra-renal failure,acute myocardial infarction,PIH,rheumatic disease,shock,stroke,and CKD were the independent risk factors for renal outcomes.During the hospitalization,almost 95%critical AKI cases were missed diagnosis,and these patients got poor outcomes.We should pay more attention to AKI during hospitalization,especially for critical patients.