1. Meconium Aspiration Syndrome
Dr Varsha Atul Shah

2.  Pulmonary Vascular Resistance
⇑ Pulmonary Venous Return
⇑ LA Pressure
Ventilation
Foramen Ovale L --> R ductus
Closes arteriosus
 PO2 shunt
⇓ RA Pressure
⇓ IVC Return
Remove Ductus
⇓ Umbilical Venous Return Venosus
Placenta Closes
 Systemic Vascular Resistance

3. 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

4. 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 %)

5. OHSU Experience: Inborn + Transfers
# Mec DR MAS MAS ECMO Died
passed intub + vent
1992-94 146 88 44 28 4 3*
1995-97 154 92 39 25 1 1*
Total 300 180 83 53 5 4
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

6. 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

7. Meconium in Amniotic Fluid
Intrapartum suctioning of mouth,
nose, pharynx
Infant Depressed
Infant Active
Intubate and suction
Observe
trachea
Other resuscitation as indicated

8. Meconium Aspiration
Syndrome
Pathophysiology
 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)

9. Meconium Aspiration
Syndrome
Diagnosis
 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

11. Meconium Aspiration Syndrome
Treatment
 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

12. Other Things to Watch For
 Hypoxia
 Acidosis
 Hypoglycemia
 Hypocalcemia
 End-organ damage due to perinatal
asphyxia

13. Meconium Aspiration Syndrome
Outcome
 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 16:358, 1993

14. Meconium Aspiration Syndrome
Surfactant Treatment
Methods
 < 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 > 50%, MAP > 7, a:A PO2 < 0.22
 Endpoint = improvement in OI and a:A PO2
 No difference in groups
Findlay et al. Pediatrics 97 (1): 48, 1996.

15. Meconium Aspiration Syndrome
Surfactant 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 a:A PO2 within 1
hour of 1st dose of surfactant
Findlay et al. Pediatrics 97 (1): 48, 1996.

16. Meconium Aspiration Syndrome
Surfactant Treatment
Control Surf P value
Air leak 5 0 0.024
ECMO 6 1 0.037
Days MV 11 (1) 8 (1) 0.047
Days O2 20 (3) 13 (1) 0.031
LOS (days) 24 (2) 16 (1) 0.003
D/C on O2 8 6 NS
Mortality (< 28 d) 0 0 NS
Findlay et al. Pediatrics 97 (1): 48, 1996.