新生兒呼吸窘迫綜合癥(Neonatal-Respiratory-Distress-Syndrome)

NeonatalRespiratoryDistressSyndrome(NRDS)Hyalinemembranedisease(HMD)

MostcommoncauseofrespiratoryfailureinthefirstdaysintheprematureinfantsReasonissurfactantinsufficientinlungswhichleadtobreathingfailureandneedtheassistantventilationOccurringin1~2%ofnewborninfants,increasesbysmallerGA:50%ofGA<28w,lessthan30%of32~36w)SurfactantKeepthelungalveoliopenStartsynthesisinGA24~28wbylungtypeIIalveolarcellsIncreasein28~35w,butproduceadequateamountsafter35wdoubleinalveolarwithin24hafterbirth,toadultlevelafter3~7dofbirthhalf-life12~24hSurfactantCompositionPhospholipid(PL)90%(neutral5%)

Phosphatidyl

cholin(PC,Lecithin)40％

Phosphatidylglycerol(PG)5％

Sphingonyeline(S)2%othersProtein 10％

A,30~35kDa,18oligomer,D,43kDa,12oligomer B,8kDa,dimer,C,4kDa,dimerFunctionofPulmonarySurfactantloweralveolarsurfacetension,reducesrespiratoryworkMaintainalveoliinflationandfunctionalresidualcapacityAcceleratelungfluidabsorption,reducealveolareffusionPathogenOpsonization,alveolarmacrophageactivation

Effects:increaseoxygenation,ameliorateventilation/perfusionanti-inflammationEtiology

Riskfactors:

Caucasianormalebabies

PreviousbirthofbabywithRDS

Cesareandelivery(morewaterinlung)PerinatalasphyxiaMultiplebirths(multiplebirthbabiesareoftenpremature)

Infantsofdiabeticmothers(toomuchinsulininababy'ssystemmaydelaysurfactantproduction)PerinatalinfectionBabieswithpatentductusarteriosus(PDA)

PathophysiologyLackofsurfactantinthelungsofinfants

AveryandMead,AmJDisChild1959

progressiveatelectasislossoffunctionalresidualcapacity(FRC)alterationofventilation-perfusionratioWeakrespiratorymusclesandcompliancyofchestwallimpairalveolarventilationDiminishedoxygenation,cyanosisandacidosisincreasedpulmonaryvascularresistance(PVR)right-to-leftshuntingthroughductusarteriovenousintrapulmanaryventilation-perfusionmismatchEtiologyandPathophysiology

Pulmonaryimmaturityresultsinsurfactantdeficiency

Alveolicollapseattheendofexpirationleadstorespiratoryfailure

Surfactantdeficiencymayariseafterasphyxia/shockandacidosisalveolarsurfacetensionishigherDiminishedPSPulmonaryatelectasisImpairedgasexchange(hypoxiaandacidosis)PulmonaryarteryhypertensionRight–to-leftheartshuntPulmonarycapillarypermeabilityincreaseFormingpulmonaryhyalinemembranePathologyatelectasis,pulmonaryedema,vascularcongestion,hemorrhage,generalizedcapillaryleakandmucosalnecrosisleadstothesmallerairfilledterminalairways;therespiratorybronchiolesandalveolarductsaresurroundedbycollapsedalveolifilledwithdebrisinanearuniformdistribution(hyalinemembranes)ClinicalPresentationPresentatbirthorfirst2to6hofbirth:respiratorydifficultythatgetsprogressivelyworse

tachypnea(rapidbreathing)

cyanosis(bluecoloring)withincreasingoxygenrequirementschestretractions

nasalflaringgruntingsoundswithbreathingCharacterizedbyprogressiveworseningofcyanosisanddyspneasymptomsusuallypeakon2to3day,andwillrecoveryafter3dDiagnosisDiagnosiscanbedecidedbyacombinationofassessments,includingGA,ahistoryofriskfactors,thesigns,chestX-rayandbloodgases.RadiographicChangesofRDS

abellshapedthoraxwithdiffuseandsymmetrical“groundglass”calledreticulogranularpatternwith“airbronchogram”,orseverebilateralopacityandobliteratethecardiacborder,

“white-outlung”

LaboratoryFindingsMixedacidosisLecithin(L)/Sphingomyelin(S)<2:1;orPhosphatidylglycerol(PG)negativeFoamTest:Inatube

+95%ethanol,1ml

+amnioticfluid(gastricjuice),1ml

shake:15”,staticstates:15”,evaluation:bubblepresentDifferentialDiagnosis

allthecausesofrespiratorydistress

“Wetlung”ortransientrespiratorydistress

AmnioticfluidormeconiumaspirationsyndromeGroupBhemolyticStreptococcuspneumonia

Diaphragmatichernia

PneumothoraxDifferentialDiagnosis–MeconiumAspiration

nodularnonhomogeneousdensities(bilateral,irregularcoarseinfiltrates),mayhavepleuraleffusions,usuallyhasanincreasedlungvolume.

DifferentialDiagnosis--Wetlung

mildcardiomegalyandbilateralreticulonodulardensitiesthatradiatefromthehila;atelectasisintheupperlobes

intervalclearanceofthereticulonodulardensitiesinthesamepatient1daylater.TreatmentSupportivetreatment:MaintainaneutralthermaltemperatureAdministeradequatefluidsandelectrolytes,preventfluidoverload

Correctacid-basedisturbances

Specifictherapy

Surfactantreplacementtherapy(natural/synthetic)--Endotracheal

intubation,Dose:50to200mg/kgContinuouspositiveairwaypressure(CPAP)Closureofthepatentductus

arteriosus（PDA）

--indomethacintherapyAntibioticRespiratoryManagementContinuousPositiveAirwayPressure(CPAP)

Indication:whenFiO2>0.6,PaO2<50mmHgorTcSO2<85%

Pressure:4~10cmH2O,flow5L/min,32°C,humidity100%ConventionalMechanicalVentilation(CMV)

Indication:PaO2<50mmHgorTcSO2<85%withCPAP(8cm);PCO2>70mmHg;orfrequentapnea

Complication:PAL(pulmonaryairleak)BPD(bronchopulmonarydysplasia;orCLD)Retinopathyofprematurity(ROP)VAP(ventilator-associatedpneumonia)ApplicationofPulmonarySurfactantIntratrachealinstillation:50~200mg/kg,6~12hintervalNeonatalRespiratoryDistressSyndrome(NRDS)meconiumaspirationsyndrome(MAS)PneumonicRespiratoryfailureAcutelunginjury,ARDSRespiratoryfailureafteropen-chestsurgeryorlungtransplantationPreventionAvoidanceofpretermbirth:

mostimportantCar