Changes And Significance Of Serum Intestinal Fatty Acid Binding Protein And D-lactate In Children With Traumatic Brain Injury Associated With Gastrointestinal Dysfunction

Background and PurposeWith the rapid development of today’s society,the incidence and mortality of traumatic brain injury（TBI）in children with accidental injuries are increasing year by year.It can also be seen from the data reported by the US Centers for Disease Control in recent years that TBI has become the leading cause of accidental deaths in children over the age of one.In China,TBI has gradually become one of the most common critical illnesses in pediatric intensive care unit（PICU）.In clinic,most children with TBI had no abnormal changes in gastrointestinal function before the accident happened.Sudden brain injury and related complications caused different degrees of damage to the gastrointestinal function of the children.After TBI,the body is in a state of stress.Because of the particularity of the development of nervous system and gastrointestinal function in children,it is easy to cause gastrointestinal mucosa hypoxic ischemia,increased permeability,imbalance of inherent flora and endotoxin translocation.Acute gastrointestinal injury（AGI）and gastrointestinal dysfunction（GID）are prone to exacerbate systemic inflammation.Without timely diagnosis and treatment,they may even cause inflammation cascades,which may lead to multiple organ dysfunction syndrome（MODS）,which is difficult to reverse.Once MODS occurs,the mortality rate of children will increase sharply.Especially in PICU,gastrointestinal function has become an important index to measure the severity of critical illness,predict the development and change of illness and prognosis.At present,there is no unified and widely used criteria for evaluating gastrointestinal function in clinical practice,and the guiding literature in pediatrics is even scarcer.The European Society of Intensive Care Medicine（ESICM）published the definition and classification criteria of AGI in 2012.According to different clinical manifestations,AGI was classified into grades I-IV.With the increase of grade,the severity of gastrointestinal function damage is more serious,and the clinical symptoms are more prominent.However,this grading standard requires a high level of experience and judgment ability of clinical doctors,and is greatly influenced by subjective factors.There may be great discrepancies in the evaluation results of different doctors.Therefore,it is important to find objective biomarkers for the early diagnosis and prognosis evaluation of gastrointestinal dysfunction.Intestinal fatty acid binding protein（IFABP）is a water-soluble protein with low molecular weight that exists only at the top of human mature intestinal villi.It has high content and high tissue-organ specificity.In the early stage of gastrointestinal mucosal injury,the integrity of normal cell membrane at the top of intestinal epithelial villi was destroyed,which increased the permeability of cell membrane,and the necrotic intestinal villi released a large amount of IFABP into human blood circulation.Therefore,the elevated level of IFABP in the blood indicates the degree of damage to intestinal epithelial cells,which is a sensitive indicator of early gastrointestinal mucosal damage.D-lactate is a metabolite produced by anaerobic fermentation of inherent bacteria in human gastrointestinal tract.Human tissues do not produce D-lactate.Because of the lack of specific metabolic enzymes,D-lactate can not be rapidly metabolized.Because of the tissue specificity of D-lactate,a sudden increase in D-lactate concentration may be an indicator of bacterial translocation.When the body suffers from severe infection and/or trauma,due to the high sensitivity of gastrointestinal mucosa to ischemia and hypoxia,the top epithelium of mucosa falls off,the mucosal barrier is damaged,and the permeability is increased,resulting in a large amount of D-lactate released into the blood.Therefore,elevated D-lactate concentration in blood is a specific marker reflecting the damage of gastrointestinal mucosal barrier function and increased permeability.Current studies have found that serum IFABP and D-lactate are closely related to early gastrointestinal dysfunction and prognosis in severe adult patients with multiple trauma,pancreatitis and sepsis.But they are rarely reported in detail in children with brain trauma.Because most researchers believe that IFABP has high sensitivity and D-lactate has high specificity,and IFABP tends to evaluate the damage degree of intestinal epithelial cells,D-lactate tends to evaluate the intestinal epithelial barrier function,the combination of the two can reflect the gastrointestinal function more accurately and comprehensively.In this study,serum IFABP and D-lactate levels were measured on the day of admission and the third day of admission.The correlation between IFABP and D-lactate levels and the severity of TBI and the grading of AGI was analyzed.The diagnostic value of IFABP and D-lactate levels in children with TBI associated with AGI was also discussed.Object and Methods1.From January 2017 to March 2018,95 children with TBI who were hospitalized in the PICU of the First Affiliated Hospital of Zhengzhou University were selected as the experimental group.According to the modified Glasgow coma scoring method and the clinical classification standard of acute closed brain injury,the experimental group was divided into three groups according to the degree of brain injury（43 mild cases,23 moderate cases and 29 severe cases）.According to the classification standard of AGI issued by ESICM,the degree of gastrointestinal function injury in children with TBI was classified into AGI I-IV grades（42 cases of AGI I,30 cases of AGI II,13 cases of AGI III and 10 cases of AGI IV）.Thirty healthy children from the same period to the health check-up of the children’s health clinic in our hospital were selected as healthy control group.2.Peripheral blood samples were collected from children with TBI at admission and on the third day after admission,respectively.Peripheral blood samples were collected in the control group during outpatient physical examination.3ml of peripheral blood was collected by vacuum blood collection with gel/coagulant of 3.5 ml.Stay at room temperature for 30 minutes.After centrifugation for 10minutes with a high-speed centrifuge of 1000×g,1.5 ml of serum was separated from the upper layer after centrifugation,then transferred to a centrifugal tube of 1.5 ml and labeled.Store in the cryogenic refrigerator of-80 degrees Celsius for inspection.The serum levels of IFABP in healthy control group and experimental group were measured by human IFABP enzyme-linked immunosorbent assay kit from the US R&D Company.The human D-lactate colorimetric assay kit of the US Biovision Company was used to determine the serum D-lactate concentration in healthy control group and experimental group.All the experiments were carried out according to the kit instructions.3.The experimental data were analyzed and processed by SPSS 22.0 software.Firstly,the normality test and the homogeneity test of variance for all the data are carried out.The measurements which conform to normal distribution and have homogeneous variances are expressed as mean±standard deviation.one-way ANOVA analysis of variance was used for comparison among groups,and least significant difference（LSD）was used for comparison between groups,and paired sample t test was used for comparison in each group.The measurement data of non-normal distribution are expressed as median（inter-quartile range）[M(P₂₅,P₇₅)]and rank sum test is used.The counting data were examined by chi-square square test.Spearman rank correlation analysis was performed on IFABP,D-lactate,brain injury degree and AGI classification.The receiver operating characteristic curve（ROC）curve was drawn to evaluate the diagnostic value of serum IFABP and D-lactate in children with traumatic brain injury associated with gastrointestinal dysfunction.P<0.05 was statistically significant.Results1.General data analysis:A total of 95 hospitalized children who met the inclusion criteria were selected as the experimental group.According to the degree of TBI,there were 43 children in mild brain injury group,including 24 males and 19females,with a median age of 4.00（3.00,7.00）.There were 23 children in moderate brain injury group,including 14 males and 9 females,with a median age of 3.00（2.00,6.00）.There were 29 children in severe brain injury group,including 15 males and 14females,with a median age of 4.00（3.00,5.50）.According to AGI classification of children with TBI,there were 42 children in AGI I group,including 23 males and 19females,with a median age of 4.00（2.00,6.25）years.There were 30 children in AGI II group,including 19 males and 11 females,with a median age of 4.00（3.00,7.00）.There were 13 children in AGI III group,including 7 males and 6 females,with an average age of 4.77±1.87 years.There were 10 children in AGI IV group,including4 males and 6 females,with an average age of 4.00±1.63 years.Finally,healthy children who met the inclusion criteria were selected as the healthy control group.A total of 30 cases,including 17 males and 13 females,with a median age of 4.00（3.00,7.25）years.There was no significant difference in age and sex among groups（all P>0.05）.2.Analysis of serum intestinal fatty acid binding protein concentration:The serum IFABP levels of all TBI groups at admission were higher than those of healthy control group.（all P<0.01）,and with the aggravation of TBI,the serum IFABP concentration increased gradually,with statistical significance（all P<0.01）.The serum IFABP level of AGI I-IV group on admission day was higher than that of control group（all P<0.01）,and with the increase of AGI level,the serum IFABP level also increased gradually,with statistical significance（all P<0.01）.The level of serum IFABP was significantly lower on the 3rd day of admission in all levels of TBI group and AGI group than that at admission,and the difference was statistically significant（P<0.01）.3.The serum D-lactate levels of all TBI groups at admission and on the third day of admission were higher than those of healthy control group.（all P<0.01）.With the aggravation of TBI,the concentration of serum D-lactate increased gradually,and the difference was statistically significant（all P<0.01）.The level of serum D-lactate in all TBI groups at the 3rd day of admission was significantly lower than that at admission（P<0.01,0.01,0.01）.The serum D-lactate level of AGI I-IV group on admission day and on the third day of admission was significantly higher than that of healthy control group（all P<0.01）,and with the increase of AGI level,the serum D-lactate level also increased gradually,with statistical significance（all P<0.01）.The level of serum D-lactate in AGI groups on the third day of admission was significantly lower than that at admission（P<0.01,0.03,0.02,0.01）.4.Relevance analysis:The level of serum IFABP at admission was positively correlated with the severity of brain injury（r_s=0.82,P<0.01）,and positively correlated with AGI classification（r_s=0.70,P<0.01）.On the third day of admission,there was no linear correlation between serum IFABP level and the severity of brain injury and AGI grade（all P>0.05）.The level of serum D-lactate was positively correlated with the severity of brain injury（r_swere 0.66 and 0.77,respectively,P<0.01）and AGI classification（r_swere 0.79 and 0.83,respectively,P<0.01）.5.Diagnostic value analysis:ROC curve analysis showed that serum IFABP level had a higher accuracy in diagnosing AGI in children with brain injury.The area under curve（AUC）was 0.88,and the 95%confidence interval was（0.82-0.94）.When the optimal truncation value was 431.34 pg/mL,the sensitivity,specificity and Yoden index were 71.61%,90.00%and 0.62 respectively.ROC curve analysis showed that the accuracy of serum D-lactate level in diagnosis of AGI in children with brain injury was very high,AUC was 0.93,95%confidence interval was（0.89-0.98）.When the optimal truncation value was 22.53 ug/mL,the sensitivity,specificity and Yoden index were 77.89%,96.67%and 0.75 respectively.Conclusion1.Serum IFABP and D-lactate are sensitive and specific biochemical indicators for early evaluation of gastrointestinal function injury in children with TBI.2.Serum IFABP and D-lactate acid have high diagnostic value in children with TBI associated with gastrointestinal dysfunction.