Association Between NT-proBNP Level On 7th Day And Length Of Hospital Stay Among Very Preterm Infants

Background and objectivesIn recent years,with the progress of perinatal medicine,the mortality of preterm infants has decreased significantly,but their long hospital stay has caused a huge burden to the family and national health finance.Therefore,it is necessary to carry out research to explore the risk factors of prolonged hospital stay of preterm infants.In adults with heart disease,N-terminal pro B-type natriuretic peptide(NT-proBNP)is related to the length of hospital stay(LOS)and could be used as a reliable index to predict LOS.However,in the field of neonates,no research has shown that there the association between NT-proBNP and LOS.Therefore,the purpose of this study is to explore the correlation between the level of cardiac function index,NT-proBNP,and the length of hospitalization in the early postnatal period among very preterm infants(VPI),so as to lay a foundation for further exploring early indicators for predicting the length of hospitalization of VPI.MethodsWe collected the data of very preterm infants born in the First Affiliated Hospital of Zhengzhou University and admitted by NICU after birth from December 20,2016 to April 30,2021,and conducted a retrospective study.Exclusion criteria:congenital disease or severe malformation;died during hospitalization;transferred from other hospitals;discharge without doctor’s consent.Main exposure factors:NT-proBNP level in serum on the 7th day after birth.Main results:late discharge(postmenstrual age at discharge was in the fourth quartile(highest)among infants born at the same GA).The incidence of premature infant diseases such as nosocomial infection,necrotizing enterocolitis(NEC)and bronchopulmonary dysplasia(BPD).Results1.From December 20,2016 to April 30,2021,a total of 942 very preterm infants were admitted to neonatal NICU in our hospital after birth.A total of 709 very preterm infants were included in this study according to theInclusion and exclusion.Of the 709 very preterm infants,327(46.1%)were female and 327(53.9%)were male.2.Univariate analysis showed that gestational age,birth weight,small for gestational age,serum creatinine level and HSPDA on the 7th day after birth,mechanical ventilation within the 1st week after birth and gestational hypertension might be potential confounding factors,which were adjusted in the subsequent statistical analysis.After the population was divided into three tertile(T1,T2 and T3 group)according to the level of exposure factors,multivariate analysis showed that compared with T1 group,infants in T3 group had an 7.4-fold increased probability of late discharge.With the increase of NT-proBNP level,the risk of late discharge increased(P for trend<0.05).The results of subgroup analysis showed that the result was still stable when the population was grouped by gestational age,gender,small for gestational age,embryo transfer,age of mom,mode of delivery,gestational hypertension and mechanical ventilation within the 1st week after birth(all P for trend<0.05,all P for interaction>0.05).3.There is a nonlinear(S-shaped curve)relationship between LnNT-proBNP7 and late discharge.The LnNT-proBNP7 values corresponding to the two inflection points are 7.5 and 9.0,respectively.When LnNT-proBNP7<7.5,the risk of late discharge did not increase with the increase of LnNT-proBNP7(or=0.6;95%CI,0.2-1.6;P=0.333);When 7.5<LnNT-proBNP7<9.0,the risk of late discharge increased with the increase of LnNT-proBNP7(or=5.0;95%CI,2.4-10.6;P<0.001);When LnNT-proBNP7≥9.0,the risk of late discharge no longer increased significantly with the increase of LnNT-proBNP7(or=1.1;95%CI=0.2-6.1;P=0.888).4.According to the turning points of curve fitting,preterm infants were divided into three groups.The analysis found that the incidence of BPD,NEC,nosocomial infection and any of the above diseases was highest in LnNT-proBNP7≥9.0 group and the lowest in LnNT-proBNP7<7.5 group.Conclusion:1.Higher NT-proBNP7 levels were associated with longer hospitalization in very preterm infants born at 28-31 gestation age;2.The relationship between LnNT-proBNP7 and late discharge was S-shaped.LnNT-proBNP7 was positively related with late discharge when LnNT-proBNP7 was between 7.5 and 9.