Meconium aspiration syndrome_

Meconium Aspiration Meconium Aspiration Syndrome (MAS) Syndrome (MAS)

Dr. Amlendra K.YadavDr. Amlendra K.YadavDr. Bipin KarkiDr. Bipin Karki

Resident (Phase-A)Resident (Phase-A)NeonatologyNeonatology

(BSMMU)(BSMMU)

ObjectivesObjectives DefinitionDefinition Epidemiology Epidemiology EtiologyEtiology PathophysiologyPathophysiology Clinical featuresClinical features Differential DiagnosisDifferential Diagnosis DiagnosisDiagnosis ManagementManagement PrognosisPrognosis

DefinitionDefinition

Meconium aspiration syndrome Meconium aspiration syndrome (MAS) is a respiratory distress in (MAS) is a respiratory distress in

an infant born throughan infant born through Meconium stained amniotic fluid Meconium stained amniotic fluid

whose symptoms cannot be whose symptoms cannot be otherwise explained.otherwise explained.

EpidemiologyEpidemiology

MSAF observed in (8-20)% of all MSAF observed in (8-20)% of all births.births.

MAS occurs in 5% of newborns MAS occurs in 5% of newborns delivered through MSAF. delivered through MSAF.

It is a disease of Term or Post-term It is a disease of Term or Post-term Infant.Infant.

Composition of meconium

Epithelial cells Fetal hair Mucus Bile

Cause of MSAFCause of MSAF Normally The passage of meconium from Normally The passage of meconium from

the fetus into amnion is prevented by lack the fetus into amnion is prevented by lack of peristalsis(low motilin level) , tonic of peristalsis(low motilin level) , tonic contraction of the anal sphincter, terminal contraction of the anal sphincter, terminal cap of viscous meconium.cap of viscous meconium.

Fetal maturation post term(high motilin Fetal maturation post term(high motilin level)level)

Vagal stimulation by cord or head Vagal stimulation by cord or head compression in absence of fetal distress.compression in absence of fetal distress.

In utero stress(hypoxia, acidosis)producing In utero stress(hypoxia, acidosis)producing relaxation of anal sphincter.relaxation of anal sphincter.

Risk factors for MASRisk factors for MAS Maternal HTMaternal HT Maternal DMMaternal DM Maternal heavy cigarette smokingMaternal heavy cigarette smoking Maternal chronic respiratory or Cardio Maternal chronic respiratory or Cardio

vascular diseasevascular disease Post term pregnancyPost term pregnancy Pre-eclampsia/eclampsiaPre-eclampsia/eclampsia OligohydramniosOligohydramnios IUGRIUGR Abnormal fetal HR patternAbnormal fetal HR pattern

PathophysiologyMechanical obstruction of

airways Thick and viscous meconium lead to Complete or partial airway

obstruction. With onset of respiration – meconium

migrates from central to peripheral airways.

Complete obstruction – atelectasis Partial obstruction – - Ball-valve – air trapping. - Risk of pneumothorax - 15 – 33%

Pathophysiology

Chemical pneumonitis: with distal progressing of meconium chemical pneumonitis develop resulting bronchiolar edema and narrowing of the small airway.

Surfactant inactivation: Bilirubin, fatty acid, triglycerides, cholesterol content of meconium inhibit surfactant function and inactivation.

Pathophysiology

Pulmonary hypertension: meconium in lungs stimulate release of proinflammatory cytokines and vasoactive substance which cause pulmonary vasoconstriction. Also hypoxia, acidosis, and hyperinflation contribute to pulmonary hypertension.

CLINICAL FEATURESCLINICAL FEATURESHistoryHistory

Infants with MAS must have a Infants with MAS must have a history of MSAF.history of MSAF.

They often are Term or post-term They often are Term or post-term IUGR. IUGR. Many are depressed at birth. Many are depressed at birth.

CLINICAL FEATURES CLINICAL FEATURES Physical examinationPhysical examination

Evidence of postmaturity: peeling skin, long Evidence of postmaturity: peeling skin, long fingernails, and decreased vernix. fingernails, and decreased vernix.

The vernix, umbilical cord, and nails may be The vernix, umbilical cord, and nails may be meconium-stained, depending upon how long meconium-stained, depending upon how long the infant has been exposed in utero. the infant has been exposed in utero.

In general, nails will become stained after 6 In general, nails will become stained after 6 hours and vernix after 12 to 14 hours of hours and vernix after 12 to 14 hours of exposure . exposure .

umbilical cord staining (thick-15min, thin-umbilical cord staining (thick-15min, thin-1hour)1hour)

Umbilical cord stained with meconium


Affected patients typically have Affected patients typically have respiratory distress with marked respiratory distress with marked tachypnea and cyanosis. tachypnea and cyanosis.

Use of accessory muscles of respiration Use of accessory muscles of respiration are evidenced by intercostal and are evidenced by intercostal and subcostal retractions and abdominal subcostal retractions and abdominal (paradoxical) breathing, often with (paradoxical) breathing, often with grunting and nasal flaring.grunting and nasal flaring.


The chest typically appears barrel-shaped, The chest typically appears barrel-shaped, with an increased anterior-posterior diameter with an increased anterior-posterior diameter caused by overinflation. caused by overinflation.

Auscultation reveals rales and rhonchi -Auscultation reveals rales and rhonchi -immediately after birth.immediately after birth.

Some patients are asymptomatic at birth and Some patients are asymptomatic at birth and develop worsening signs of respiratory develop worsening signs of respiratory distress as the meconium moves from the distress as the meconium moves from the large airways into the lower tracheobronchial large airways into the lower tracheobronchial tree.tree.

Differential Diagnosis

Perinatal Asphyxia Bacterial Pneumonia Respiratory Distress Syndrome Transient Tachypnea Of Newborn Congenital Heart Disease

DiagnosisDiagnosis

MAS must be considered in any MAS must be considered in any infant born through MSAF who infant born through MSAF who develops symptoms of RD with develops symptoms of RD with

typical chest x ray findingstypical chest x ray findings

DiagnosisDiagnosis

A chest radiographs shows A chest radiographs shows hyperinflation of the lung field and hyperinflation of the lung field and flatten diagphragms.flatten diagphragms.

There are coarse irregular patchy There are coarse irregular patchy infiltrates infiltrates

A pneumothorax and A pneumothorax and pneumomediastinum may be present pneumomediastinum may be present ..

Coarse irregular patchy infiltrate with Coarse irregular patchy infiltrate with emphysema.emphysema.

Areas of opacification due to Areas of opacification due to atelectasis bilaterally. atelectasis bilaterally.

left lung demonstrating the streaky lucencies of the left lung demonstrating the streaky lucencies of the air in the interstitium air in the interstitium (red arrows)(red arrows) complicated by a complicated by a

pneumothoraxpneumothorax (yellow arrow).(yellow arrow).

DiagnosisDiagnosis

Arterial blood gas measurements Arterial blood gas measurements typically show hypoxemia and typically show hypoxemia and hypercarbia. hypercarbia.

Infants with pulmonary hypertension Infants with pulmonary hypertension and right-to-left shunting may have a and right-to-left shunting may have a gradient in oxygenation between gradient in oxygenation between preductal and postductal samples. preductal and postductal samples.

Echocardiogram for evaluation of PPH.Echocardiogram for evaluation of PPH.

Management

Prenatal management: Key management lies in prevention during prenatal period.

Identification of high risk pregnancies and close monitoring. Pregnancy that continue past due date, induction as early as 41 weeks may help prevent meconium aspiration.

If there is sign of fetal distress corrective measure should be undertaken or infant should be delivered in timely manner.

Management Management

ManagementManagement

When the infant is not vigorous:When the infant is not vigorous:1.1. Clear airways as quickly as possible.Clear airways as quickly as possible.

2.2. Free flow 0Free flow 02.2.

3.3. Radiant warmer but drying and Radiant warmer but drying and stimulation should be delayed.stimulation should be delayed.

4.4. Direct laryngoscopy with suction of the Direct laryngoscopy with suction of the mouth and hypopharynx under direct mouth and hypopharynx under direct visualization, followed by intubation and visualization, followed by intubation and then suction directly to the ET tube .then suction directly to the ET tube .

5.5. The process is repeated until either The process is repeated until either ‘‘little additional meconium is recovered, ‘‘little additional meconium is recovered, or until the baby’s heart rate indicates or until the baby’s heart rate indicates that resuscitation must proceed without that resuscitation must proceed without delay’’.delay’’.

Postnatal ManagementPostnatal Management

Apparently Apparently well childwell child born through born through MSAFMSAF

Most of them do not require any Most of them do not require any interventions besides close interventions besides close monitoring for RD. monitoring for RD.

Most infants who develop symptoms Most infants who develop symptoms will do so in the first 12 hours of life.will do so in the first 12 hours of life.

Postnatal ManagementPostnatal Management

Approach to the Approach to the ill newbornsill newborns:: Transfer to NICU.Transfer to NICU. Monitor closely.Monitor closely. Full range of respiratory support Full range of respiratory support

should be given.should be given. Sepsis w/up and ABx indicated.Sepsis w/up and ABx indicated.

Treatment in NICUTreatment in NICU

Goals:Goals: Increased oxygenation while minimizing Increased oxygenation while minimizing

the barotrauma (may lead to air leak).the barotrauma (may lead to air leak). Prevent pulmonary hypertension. Prevent pulmonary hypertension. Successful transition from intrauterine Successful transition from intrauterine

to extrauterine life with a drop in to extrauterine life with a drop in pulmonary arterial resistance and an pulmonary arterial resistance and an increase in pulmonary blood flow.increase in pulmonary blood flow.

Treatment in NICUTreatment in NICU Ventilatory supportVentilatory support depends on the depends on the

amount of respiratory distress:amount of respiratory distress:

OO22 hood hood CPAPCPAP Mechanical ventilation Mechanical ventilation HFV should reduce air leaks. High-frequency ventilators may slow the High-frequency ventilators may slow the

progression of meconium down the progression of meconium down the tracheobronchial tree and allow more time for tracheobronchial tree and allow more time for meconium removal.meconium removal.


surfactant therapy in MAS showed promising results with decrease in the number of infants requiring ECMO and possible reduction of pneumothorax


Inhaled Nitric oxide (NO) Selective pulmonary vasodilation. Activate guanylate cyclase and

increases cyclic GMP and acting directly on the vascular smooth muscle.

Decreased need for ECMO but no difference in mortality.

Pretreatment with surfactant improves in delivery of iNO to the alveoli.

ECMOECMO

40% of infants with MAS treated with 40% of infants with MAS treated with inhaled NO fail to respond and inhaled NO fail to respond and require ECMO.require ECMO.

35% of ECMO patients are with MAS.35% of ECMO patients are with MAS. Survival rate after ECMO 93-100%.Survival rate after ECMO 93-100%.

ProgonosisProgonosis

Mortality reduced to <5% with new Mortality reduced to <5% with new modalities of therapy such as modalities of therapy such as administration of surfactant, HFV, iNO, administration of surfactant, HFV, iNO, ECMO.ECMO.

Chronic lung disease may result from Chronic lung disease may result from prolong mechanical ventilation prolong mechanical ventilation

Those with significant asphyxial insult Those with significant asphyxial insult may demonstrate neurologic sequele.may demonstrate neurologic sequele.

SummarySummary

Optimal care of an infant born Optimal care of an infant born through MSAF involves close through MSAF involves close collaboration between OBs and collaboration between OBs and Neonatoloy team.Neonatoloy team.

Effective communication and Effective communication and anticipation of potential problems is anticipation of potential problems is a corner stone of the successful a corner stone of the successful partnership.partnership.

Education

Meconium aspiration syndrome_