Meconium aspiration syndrome_

1. Meconium Aspiration Meconium Aspiration
Syndrome (MAS) Syndrome (MAS)
Dr. Amlendra K.YadavDr. Amlendra K.Yadav
Dr. Bipin KarkiDr. Bipin Karki
Resident (Phase-A)Resident (Phase-A)
NeonatologyNeonatology
(BSMMU)(BSMMU)

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

3. DefinitionDefinition
Meconium aspiration syndrome Meconium aspiration syndrome
(MAS) is a respiratory distress in an (MAS) is a respiratory distress in an
infant born throughinfant born through
Meconium stained amniotic fluid Meconium stained amniotic fluid
whose symptoms cannot be whose symptoms cannot be
otherwise explained.otherwise explained.

4. EpidemiologyEpidemiology

MSAF observed in (8-20)% of all births.MSAF observed in (8-20)% of all births.

MAS occurs in 5% of newborns delivered MAS occurs in 5% of newborns delivered
through MSAF. through MSAF.

It is a disease of Term or Post-term It is a disease of Term or Post-term
Infant.Infant.

5. Composition of meconium
Epithelial cells
Fetal hair
Mucus
Bile

6. Cause of MSAFCause of MSAF

Normally The passage of meconium from the Normally The passage of meconium from the
fetus into amnion is prevented by lack of fetus into amnion is prevented by lack of
peristalsis(low motilin level) , tonic contraction of peristalsis(low motilin level) , tonic contraction of
the anal sphincter, terminal cap of viscous the anal sphincter, terminal cap of viscous
meconium.meconium.

Fetal maturation post term(high motilin level)Fetal maturation post term(high motilin level)

Vagal stimulation by cord or head compression Vagal stimulation by cord or head compression
in absence of fetal distress.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.

7. 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 vascular Maternal chronic respiratory or Cardio vascular
diseasedisease

Post term pregnancyPost term pregnancy

Pre-eclampsia/eclampsiaPre-eclampsia/eclampsia

OligohydramniosOligohydramnios

IUGRIUGR

Abnormal fetal HR patternAbnormal fetal HR pattern

8. Pathophysiology
Mechanical 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%

9. 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.

10. 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.

12. CLINICAL FEATURESCLINICAL FEATURES
HistoryHistory

Infants with MAS must have a history Infants with MAS must have a history
of MSAF.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.

13. 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-1hour)umbilical cord staining (thick-15min, thin-1hour)

14. Umbilical cord stained with meconium

15. CLINICAL FEATURES CLINICAL FEATURES
Physical examinationPhysical examination    

Affected patients typically have respiratory Affected patients typically have respiratory
distress with marked tachypnea and distress with marked tachypnea and
cyanosis. 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.

16. CLINICAL FEATURES CLINICAL FEATURES
Physical examinationPhysical examination    

The chest typically appears barrel-shaped, with The chest typically appears barrel-shaped, with
an increased anterior-posterior diameter caused an increased anterior-posterior diameter caused
by overinflation. 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 distress develop worsening signs of respiratory distress
as the meconium moves from the large airways as the meconium moves from the large airways
into the lower tracheobronchial tree.into the lower tracheobronchial tree.

17. Differential Diagnosis
Perinatal Asphyxia
Bacterial Pneumonia
Respiratory Distress Syndrome
Transient Tachypnea Of Newborn
Congenital Heart Disease

18. DiagnosisDiagnosis
MAS must be considered in any infant MAS must be considered in any infant
born through MSAF who develops born through MSAF who develops
symptoms of RD with typical chest x symptoms of RD with typical chest x
ray findingsray findings

19. DiagnosisDiagnosis

A chest radiographs shows hyperinflation A chest radiographs shows hyperinflation
of the lung field and flatten diagphragms.of the lung field and flatten diagphragms.

There are coarse irregular patchy There are coarse irregular patchy
infiltrates infiltrates

A pneumothorax and pneumomediastinum A pneumothorax and pneumomediastinum
may be present .may be present .

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

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

22. left lung demonstrating the streaky lucencies of the air in left lung demonstrating the streaky lucencies of the air in
the interstitium the interstitium (red arrows)(red arrows) complicated by a complicated by a
pneumothoraxpneumothorax (yellow arrow).(yellow arrow).

23. DiagnosisDiagnosis

Arterial blood gas measurements typically Arterial blood gas measurements typically
show hypoxemia and hypercarbia. show hypoxemia and hypercarbia.

Infants with pulmonary hypertension and Infants with pulmonary hypertension and
right-to-left shunting may have a gradient right-to-left shunting may have a gradient
in oxygenation between preductal and in oxygenation between preductal and
postductal samples. postductal samples.

Echocardiogram for evaluation of PPH.Echocardiogram for evaluation of PPH.

24. 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.

25. Management Management

26. 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 0
2 .2 .
3.3.Radiant warmer but drying and stimulation Radiant warmer but drying and stimulation
should be delayed.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 ‘‘little The process is repeated until either ‘‘little
additional meconium is recovered, or until additional meconium is recovered, or until
the baby’s heart rate indicates that the baby’s heart rate indicates that
resuscitation must proceed without delay’’.resuscitation must proceed without delay’’.

27. 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 monitoring for interventions besides close monitoring for
RD. RD.

Most infants who develop symptoms will Most infants who develop symptoms will
do so in the first 12 hours of life.do so in the first 12 hours of life.

28. 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 should be Full range of respiratory support should be
given.given.

Sepsis w/up and ABx indicated.Sepsis w/up and ABx indicated.

29. 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 to Successful transition from intrauterine to
extrauterine life with a drop in pulmonary extrauterine life with a drop in pulmonary
arterial resistance and an increase in arterial resistance and an increase in
pulmonary blood flow.pulmonary blood flow.

30. Treatment in NICUTreatment in NICU
Ventilatory supportVentilatory support depends on the amount of depends on the amount of
respiratory distress:respiratory distress:

OO22 hood hood

CPAPCPAP

Mechanical ventilation Mechanical ventilation
HFV should reduce air leaks.

High-frequency ventilators may slow the progression of High-frequency ventilators may slow the progression of
meconium down the tracheobronchial tree and allow meconium down the tracheobronchial tree and allow
more time for meconium removal.more time for meconium removal.

31. Treatment in NICUTreatment in NICU
surfactant therapy in MAS showed
promising results with decrease in the
number of infants requiring ECMO and
possible reduction of pneumothorax

32. Treatment in NICUTreatment in NICU
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.

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

34. ProgonosisProgonosis

Mortality reduced to <5% with new modalities of Mortality reduced to <5% with new modalities of
therapy such as administration of surfactant, therapy such as administration of surfactant,
HFV, iNO, ECMO.HFV, iNO, ECMO.

Chronic lung disease may result from prolong Chronic lung disease may result from prolong
mechanical ventilation mechanical ventilation

Those with significant asphyxial insult may Those with significant asphyxial insult may
demonstrate neurologic sequele.demonstrate neurologic sequele.

35. SummarySummary

Optimal care of an infant born through Optimal care of an infant born through
MSAF involves close collaboration MSAF involves close collaboration
between OBs and Neonatoloy team.between OBs and Neonatoloy team.

Effective communication and anticipation Effective communication and anticipation
of potential problems is a corner stone of of potential problems is a corner stone of
the successful partnership.the successful partnership.