Acute Renal Injury After Road Traffic Injury: Incidence, Prognosis, And Risk Factors

BackgroundRoad traffic injury(RTI) occurs on all continents,in every country of the world. Worldwide,an estimated 1.2 million people are killed in road crashes each year and more than half of these ones are young adults aged between 15 and 44 years. Projections of the World Health Organization(WHO) indicate that these figures will increase by about 65%by 2020,low-income and middle-income countries account for about 90%of the deaths unless there is new commitment to prevention.China is one of the most serious countries of road traffic safety problem.In 2001,China occupied the top of all countries in the rate of accident and mortality per ten thousand vehicles,which resulted in 106,000 deaths.The annual numbers of road traffic deaths rose sharply,and road traffic fatality rates rose by 4 times from 1978 to 2005. Without doubt,RTI is a growing worldwide public health problem of global. Acute kidney injury(AKI) is a clinical syndrome with high mortality in patients with severe trauma.The incidence of AKI ranged from 0.098 to 31%depending on the definition of AKI and studied populations.The mortality remained high(13 to 78%) and it was an important contributor to hospital mortality in post-traumatic population. However,we have known little so far concerning AKI after RTI though it was the most common cause of post-traumatic AKI.There is no large sample study to report the exact incidence of AKI,clinical outcome,and risk factors in patients with RTI.It is well known that prevention is better than cure for AKI,since there is no specific and effective management for the syndrome and blood purification do not improve patients' outcome.To promote clinical practice and further obtain the best outcomes for patients,it is important for clinicians to understand predictors of development and prognosis of AKI.Thus,the study was performed retrospectively in patients with RTI. In the study,we aimed to investigate independent risk factors for development and outcome of AKI in patients undergoing traffic,then offering a survival and health benefit for the patient suffered RTI.Patients and Methods1.Study populationA retrospective clinical study was performed.The NangFang Hospital and ZhuJiang Hospital is 2 academic medical centers affiliated with Sourthern Medical University.All patients with RTI admitted to both of hospitals between January 2002 and December 2006 were screened using the computerized hospital admissions and discharges database.Following patients were excluded from the study cohort:on chronic dialysis before traffic,staying in hospital less than 24 hrs,neither serum creatinine(Scr) value nor urine output record after the traffic.If a patient had more than one admission during the study period,only the first admission was included in the study.As a result,4857 records were analysed in the study.2.DefinitionsAKI was diagnosed and classified according to RIFLE criteria.The _maximum RIFLE stratum(class R_max,class I_max or class F_max),which was based on the highest Scr level or the least urine output during hospital stay,was assigned to each patient for analysis.The clinical outcome of those with AKI included patient outcome and renal outcome.Complete renal recovery was defined by a convalescent Scr not more than 50%increased from baseline.e.g.if baseline Scr was 1.0 mg/dL(88 mcmol/L), complete recovery was said to occur if the new steady state SCrt was＜1.5 mg/dL (133 mcmol/L).Partial renal recovery was said to occur if the above condition for complete recovery was not met but the patient did not require chronic dialysis.3.Data collectionThe patients' information,including demographic data,clinical data and laboratory data were collected from the database.All data were inputted using Epidata3.0 software by a non-investigator data manager and repeated again,then double data were carried on consistency verification.All identifying information of patients was stripped of to preserve their anonymity.4.Statistical analysisIn statistical data,continuous variables were presented as mean±standard deviation(SD) or median(range) and categorical variables were presented as percentages.All variables were tested for normal distribution using the Kolmogorov-Smimov test.One-way analysis of variance(one-way ANOVA) test or the Kruskal-Wallis H test for continuous variables according to their distribution; Fisher's exact test or the chi-square test were applied to assess categorical data associated with RIFLE classifications(including no AKI,class R_max,class I_max and class F_max).To elucidate the impact of each category of RIFLE criterion on hospital mortality and find the risk factors for development of AKI,multiple-variable logistic regression analyses was conducted,variables at p＜0.05 in the univariate analysis and those considered clinically important were entered a multiple-variable logistic regression model.The Hosmer-Lemeshow test was employed to determine the goodness-of-fit of the model,P＞0.05 was regarded as an acceptable model.The results of multivariate logistic regression analysis were summarized by estimating odds ratios(OR) and respective 95%confidence interval(CI).We considered double-sided P＜0.05 as statistically significant.Data were analyzed using the SPSS version 13.0.Results1.Characteristic of patients with RTIDuring the study period,4857 patients admitted for traffic trauma were evaluated.Of these patients,358 patients developed AKI.The number of male was 3719(76.6%),mean age was 33.3±15.4 yrs(1-90years).70.0%(3390/4857) patients were young adults aged between 15 and 44 years,and 79.4%(3856/4857) patients were vulnerable road users who had underlying probability of a crash for particular exposure.64.6%and 49.7%patients suffered extremity and head injury which were the most frequent injured location,followed by thoracic injury(19.2%),abdominal injury(18.5%) and spinal injury(15.6%).Mean ISS was 12.9±8.7(1-75) and mean GCS was 13.1±3.5(3-15) on admission,respectively.911(18.8%) patients had one or more than one organ dysfunctions.The median of length of hospital stay was 17d (2-367d).Overall mortality during hospitalization in population with RTI was 8.4% (408/4857).2.Outcomes of patients who developed AKI after RTIThe mortality rate in patients who developed AKI was very high at 51.1% (183/358).This is in striking contrast to the mortality rate of only 5.0%(225/4499) in patients who did not develop AKI.There were significant differences in mortality rate between the population with AKI and those without AKI(P＜0.001).Of note,there was an increasing mortality with increasing severity of AKI.The mortality rate in patients of Risk_max,Injury_max or Failure_max were 29.5%,42.6%,66.1%within 14-day after injury,30.9%,45.7%,71.3%within 28-day after injury and 34.2%,46.8%,76.5%on discharge from hospital,respectively. Of 175 survived patients suffered from AKI,93.7%(164/175) patients had complete renal recovery,6.3%(11/175) had partial renal recovery and all the survived became independent of RRT at 28 days after AKI.An increasing trend was observed for the rate of left renal insufficiency in class Risk_max,class Injury_max and class Failure_max,which was 1.3%,4.3%and 7.0%respectively(P=0.019).3.Risk predictors for development of AKI and deteriorated AKIThe incidence of AKI in patients with road trauma was 7.3%(358/4857) according to the RIFLE criteria.In such patients,73.2%(262/358) of AKI occurred at the first 72 hours after trauma and 89.1%(319/358) occurred in the initial week, 10.7%(38/358) patients have pre-existing disease.The number of male and female was 183(82.8%) and 38(17.2%) respectively,mean age was 39.2±16.4 yrs(13—80years).Mean ISS was 24.4±9.0(1—75) and mean APACHEâ…¡scores was 19.6±8.3(4—42) on admission.137(61.9%) patients had additional organ dysfunctions and the mean number of organ dysfunction was 2.3±1.3(1—6).65% (233/358) patients underwent surgical operations,15(4.2%) patients required renal replacement therapy.they have a longer ICU stay and hospital stay compared to patients with no AKI.In univariate analysis,the patients with AKI were older than the patients without AKI(P=0.002),their rescue time were longer and were more severe injury assessed by ISS,APACHEâ…¡score and GCS,The occurrence of severe head injury,abdominal organ injury,thoracic organ injury and open long bone fracture were more frequent in population with AKI(P＜0.001),and the patients with AKI had higher frequencies of serious complicating morbidities including shock, rhabdomyolysis,sepsis and additional renal dysfunction than those ones without AKI (P＜0.05).We used a multivariate logistic regression model to further investigate interactions between all statistically significant factors contributing to AKI.The analysis showed that increasing age(10yrs),rescue time＞60min,severe head injury, abdominal organ injury,open long bone fracture,rhabdomyolysis,shock and respiration system dysfunction were associated with increased risk for occurrence of AKI(P＜0.05).Hosmer-Lemeshow goodness-of-fit test showed that the model was statistically significant without bias(x²=5.843,df=8,P=0.665).The patients were categorized Risk_max,Injury_max or Failure_max based on alterations in serum creatinine or urine output,which was 284(58.3%),97(19.9%) and 115(21.8%) respectively.In univariable analysis,multiple injury,severe injury assessed by ISS,APACHEâ…¡score and GCS,severe head injury,abdominal organ injury,duration of hypotension and were statistically significant predictors for deteriorated renal dysfunction.Ordinal regression analysis showed that the deteriorated AKI followed the increasing APACHEâ…¡score,ISS,decreasing GCS and prolonged time of hypotension duration(p＜0.05).Pearson test(x²=920.188, df=950,P=0.750) and Deviance test(x²=815.340,df=950,P=0.999)showed that the regression model was statistically significant without bias.4.Risk factors for mortality in patients with AKIAmong the 358 patients with AKI,51.1%(183/358) died prior to hospital discharge.The 14-day and 28-day mortality rate were 44.7%(160/358),47.8% (171/358) respectively.Several factors were associated with death in univariate analysis,including severity degree of injury assessed by ISS,APACHEâ…¡score and GCS,severe head injury and organ dysfunction syndrome including respiratory, cardiovascular,hematological,neurological and kidney.Factors not significantly associated with death in hospital included gender,age or RRT.A multivariable logistic regression model was developed to assess for independent factors associated with death in hospital for patients with AKI.The analysis showed that severe head injury,ISS＞25,RIFLE-Failure,and respiratory,cardiovascular,hematological system dysfunction were associated with poor prognosis.Hosmer-Lemeshow goodness-of-fit test showed that the model was statistically significant without bias(x²=3.592,df=8, P=0.892).5.Renal outcome in the survived and risk factors for left renal insufficiencyCompared to those that recovered completely renal function,patients that remained left renal insufficiency were more likely to be male,older age,severe AKI, required renal replacement therapy,complicated with ODS and sepsis,with a diagnosis of pre-existing disease and severe rhabdomyolysis(CK≥10000IU/L) in univariate analysis.Followed variables were associated independently with poor renal outcome on 28-day after AKI in a multivariate logistic regression analysis:sepsis, AKI-Injury_max,AKI-Failure_max and respiration system dysfunction. Hosmer-Lemeshow goodness-of-fit test showed that the model was statistically significant without bias(x²=6.012,df=8,P=0.646).ConclusionsAKI was a severe complication in the population with RTI and associated with greatly increased mortality during hospitalization,and could incapacitate the survivors because of left renal insufficiency.RIFLE criteria could contribute to predict the patient at a moderate to high risk for mortality and left renal insufficiency. Certain independent predictors such as delayed hospital rescue,severe injury assessed by ISS and severe head injury could predict patients at a high risk for development of AKI.The latter two and additional organs dysfunction were also predictors of mortality in those with AKI.Such risk predictors could assist in implementing strategies to prevent AKI and improve prognosis in patients with AKI,which should offer better outcomes for patients suffered RTI.