Meconium Aspiration Syndrome

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Meconium Aspiration Syndrome

• Edited May 2005

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• Pulmonary Vascular Resistance

• Pulmonary Venous Return

• LA Pressure

Ventilation
Foramen Ovale Closes
L --gt R ductus arteriosus shunt

• PO2

• RA Pressure

• IVC Return

Ductus Venosus Closes
Remove Placenta

• Umbilical Venous Return

• Systemic Vascular Resistance

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What is meconium aspiration

• Meconium is the first intestinal discharge of the
  newborn
• Epithelial cells fetal hair mucus bile
• Intrauterine stress may cause in utero passage of
  meconium
• Aspirated by the fetus when fetal gasping or deep
  breathing occurs stimulated by hypoxia and
  hypercarbia
• Warning sign of fetal distress

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Meconium The Stats

• Frequency of Mec stained amniotic fluid 10-25
• OF MEC stained infants
• 30 depressed at birth
• 10 meconium aspiration syndrome (range 2-36 )
• OF infants with MEC aspiration syndrome
• 17 deliver through thin meconium (range 7-35 )
  
• 35 need mechanical ventilation (range 25-60 )
• 12 die (range 5-37 )

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OHSU Experience Inborn Transfers
MAS Meconium aspiration syndrome as primary
pulmonary diagnosis No pulmonary hypoplasia or
major congenital anomalies MAS vent ventilated
with pulmonary diagnosis of MAS or PPHN ECMO
MAS infants transferred for ECMO Died 1
infant in each of the years died with a diagnosis
of severe HIE
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Risk Factors for Meconium Passage

• Postterm pregnancy
• Preeclampsia-eclampsia
• Maternal hypertension
• Maternal diabetes mellitus
• Abnormal fetal heart rate
• IUGR
• Abnormal biophysical profile
• Oligohydramnios
• Maternal heavy smoking

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Intrapartum suctioning of mouth nose pharynx
Infant Depressed
Infant Active
Intubate and suction trachea
Observe
Other resuscitation as indicated
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Meconium Aspiration SyndromePathophysiology

• Airway obstruction of large and small airways
• Inflammation and edema
• Protein leak
• Inflammatory Mediators
• Direct toxicity of meconium constituents
  chemical pneumonitis
• Surfactant dysfunction or inactivation
• Effects of in utero hypoxemia and acidosis
• Altered pulmonary vasoreactivity (PPHN)

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Meconium Aspiration SyndromeDiagnosis

• Known exposure to meconium stained amniotic fluid
• Respiratory symptoms not explained by other cause
• R/O pneumonia RDS spontaneous air leak
• CXR changes - diffuse patchy infiltrates
  consolidation atelectasis air leaks
  hyperinflation

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Meconium Aspiration SyndromeTreatment

• Ventilation strategies
• Avoid air leak check CXR with acute
  deterioration
• Prevent pulmonary hypertension - generous O2
• HFOV if unable to maintain on conventional vent
• Steroids (no human data controversial)
• ROS Antibiotics (ampicillin gentamicin)
• Surfactant
• Inhaled Nitric Oxide
• ECMO

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Other Things to Watch For

• Hypoxia
• Acidosis
• Hypoglycemia
• Hypocalcemia
• End-organ damage due to perinatal asphyxia

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Meconium Aspiration SyndromeOutcome

• High incidence long term pulmonary problems
• At 6 months - 23 MAS with regular bronchodilator
  therapy
• FRC was higher in symptomatic infants
• IPPV and O2 were not predictors of problems
• Increased risk of poor neurologic outcome due to
  perinatal insult - seizures CP mental
  retardation

Yuksel et al. Pediatric Pulmonology 16358
1993
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Meconium Aspiration SyndromeSurfactant Treatment

• Methods
• lt 6 hours old with MAS
• 20 infants randomized to receive 150 mg/kg
  surfactant by 20 minute infusion q6h x4 doses
  maximum
• On ventilator - FiO2 gt 50 MAP gt 7 aA PO2 lt
  0.22
• Endpoint improvement in OI and aA PO2
• No difference in groups

Findlay et al. Pediatrics 97 (1) 48 1996.
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Meconium Aspiration SyndromeSurfactant Treatment

• Results
• No infant received more than 3 doses
• Significant improvement in OI MAP FiO2 within
  3-6 hours after 2nd dose of surfactant
• Significant improvement in aA PO2 within 1 hour
  of 1st dose of surfactant

Findlay et al. Pediatrics 97 (1) 48 1996.
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Meconium Aspiration SyndromeSurfactant Treatment
Findlay et al. Pediatrics 97 (1) 48 1996.