1、Neonatal Respiratory Neonatal Respiratory Distress SyndromeDistress Syndrome (NRDS)(NRDS)SurfactantKeep the lung alveoli openStart synthesis in GA 2428w by lung type II alveolar cellsIncrease in 2835w,but produce adequate amounts after 35wdouble in alveolar within 24h after birth,to adult level afte
2、r 37d of birthhalf-life 1224hSurfactant CompositionPhospholipid(PL)Function of Pulmonary Surfactantlower alveolar surface tension,reduces respiratory workinflation functional residual capacity EtiologyF Risk factors:Caucasian or male babies Previous birth of baby with RDS Cesarean delivery(more wate
3、r in lung)Perinatal asphyxia Multiple births(multiple birth babies are often premature)Infants of diabetic mothers(too much insulin in a babys system may delay surfactant production)Perinatal infection Babies with patent ductus arteriosus(PDA)PathophysiologyF Lack of surfactant in the lungs of infan
4、ts Avery and Mead,Am J Dis Child 1959 progressive atelectasis loss of functional residual capacity(FRC)alteration of ventilation-perfusion ratioF Weak respiratory muscles and compliancy of chest wall impair alveolar ventilationF Diminished oxygenation,cyanosis and acidosisincreased pulmonary vascula
5、r resistance(PVR)right-to-left shunting through ductus arteriovenous intrapulmanary ventilation-perfusion mismatchEtiology and PathophysiologyF Pulmonary immaturity results in surfactant deficiencyF Alveoli collapse at the end of expiration leads to respiratory failureF Surfactant deficiency may ari
6、se after asphyxia /shock and acidosisalveolar surface tension is higherDiminished PSPulmonary atelectasisImpaired gas exchange(hypoxia and acidosis)Pulmonary artery hypertensionRightto-left heart shuntPulmonary capillary permeability increaseForming pulmonary hyaline membranePathologyatelectasis,pul
7、monary edema,vascular congestion,hemorrhage,generalized capillary leak and mucosal necrosis leads to the smaller air filled terminal airways;the respiratory bronchioles and alveolar ducts are surrounded by collapsed alveoli filled with debris in a near uniform distribution(hyaline membranes)Clinical
8、 PresentationF Present at birth or first 2 to 6 h of birth:respiratory difficulty that gets progressively worse tachypnea(rapid breathing)cyanosis(blue coloring)with increasing oxygen requirementschest retractions nasal flaring grunting sounds with breathingF Characterized by progressive worsening o
9、f cyanosis and dyspneaF symptoms usually peak on 2 to 3 day,and will recovery after 3 d DiagnosisDiagnosis can be decided by a combination of assessments,including GA,a history of risk factors,the signs,chest X-ray and blood gases.Radiographic Changes of RDS a bell shaped thorax with diffuse and sym
10、metrical“ground glass”called reticulogranular pattern with“air bronchogram”,or severe bilateral opacity and obliterate the cardiac border,“white-out lung”Laboratory FindingsF Mixed acidosisF Lecithin(L)/Sphingomyelin(S)0.6,PaO250mmHg or TcSO285%Pressure:410cm H2O,flow 5L/min,32C,humidity 100%F Conve
11、ntional Mechanical Ventilation(CMV)Indication:PaO250mmHg or TcSO270mmHg;or frequent apnea Complication:PAL(pulmonary air leak)BPD(bronchopulmonary dysplasia;or CLD)Retinopathy of prematurity(ROP)VAP(ventilator-associated pneumonia)Application of Pulmonary SurfactantIntratracheal instillation:50200mg
12、/kg,612h intervalF Neonatal Respiratory Distress Syndrome(NRDS)F meconium aspiration syndrome(MAS)F Pneumonic Respiratory failureF Acute lung injury,ARDSF Respiratory failure after open-chest surgery or lung transplantationPreventionF Avoidance of preterm birth:most importantF Careful maternal care
13、and fetal monitoringF Accelerate fetal lung maturation Maternal glucocorticoids(betamethasone,examethasone,)24h before birth Administration of a first dose of PS into the trachea of symptomatic premature infants immediately after birth or during the first 24hr of life The most effective way to preve
14、nt RDS is to prevent preterm delivery.If preterm delivery is inevitable,attempts to“mature the fetus”are reasonable.Question:What is NRDS/HMD?Which infants do not have adequate surfactant?What are risk factors of NRDS?What is the clinical course of NRDS?How do you diagnose NRDS?What are other causes of respiratory distress?How do you manage or prevent NRDS?
