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 af
2、ter 37d of birthhalf-life 1224hSurfactant CompositionPhospholipid (PL) Function of Pulmonary Surfactantlower alveolar surface tension, reduces respiratory workinflation functional residual capacity Etiology Risk factors: Caucasian or male babies Previous birth of baby with RDS Cesarean delivery (mor
3、e water 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) PathophysiologyLack of surfactant in the lun
4、gs of infants Avery and Mead, Am J Dis Child 1959 progressive atelectasis loss of functional residual capacity (FRC)alteration of ventilation-perfusion ratioWeak respiratory muscles and compliancy of chest wall impair alveolar ventilationDiminished oxygenation, cyanosis and acidosisincreased pulmona
5、ry vascular resistance (PVR) right-to-left shunting through ductus arteriovenous intrapulmanary ventilation-perfusion mismatchEtiology and Pathophysiology Pulmonary immaturity results in surfactant deficiency Alveoli collapse at the end of expiration leads to respiratory failure Surfactant deficienc
6、y may arise 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 membranePathologyatele
7、ctasis, pulmonary 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 me
8、mbranes)Clinical PresentationPresent 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 breathingCharacterized by progres
9、sive worsening of cyanosis and dyspneasymptoms 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
10、 with diffuse and symmetrical “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,
11、flow 5L/min, 32C, humidity 100%Conventional 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 Pulmo
12、nary SurfactantIntratracheal instillation: 50200mg/kg, 612h intervalNeonatal Respiratory Distress Syndrome (NRDS)meconium aspiration syndrome (MAS)Pneumonic Respiratory failureAcute lung injury, ARDSRespiratory failure after open-chest surgery or lung transplantationPreventionAvoidance of preterm bi
13、rth: most importantCareful maternal care and fetal monitoringAccelerate 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 24
14、hr of life The most effective way to prevent 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 ?
