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MECONIUM ASPIRATION SYNDROME (WHO (Maternal Factors (Maternal HTN, Pre…
MECONIUM ASPIRATION SYNDROME
WHO
Term + post-term infants more common
Infants with foetal distress in utero or at birth
10-15% of births mec-stained amniotic fluid
4-10% of these infants then develop MAS
Depressed foetus
From 36 weeks GA - incidence increases w/GA
Maternal Factors
Maternal HTN
Pre-eclampsia
Placental insufficiency
Oligohydramnios
Infection or chorioamnionitis
Drug abuse
WHAT
presence of meconium in tracheobronchial airways
small particles diffuse + spread
Lower airway obstruction
Infection
Chemical inflammation
Atelectasis
Mechanical obstruction
complete
Atelectasis
R to L shunts
Decreased PaO2
1 more item...
Incomplete
Ball valve obstruction (air trapping)
Air Leaks
Increased PaCO2
1 more item...
Surfactant inactivation
Atelectasis
Large plugs
Upper airway obstruction
acute hypoxia
Newborn aspirates meconium stained amniotic fluid
in utero or during labour
causes VQ mismatch
Diagnosis made if mec-stained amniotic fluid at delivery + resp distress
Confirmed with xray
Atelectasis
Consolidation interspersed w/hyperexpanded zones
Air leaks + pleural effusions + ?pneumothorax
WHERE
Trachea and bronchioles - airways
In utero or at delivery - mec-stained amniotic fluid swallowed
mec from airways absorbed and excreted in urine
WHEN
Aspirate meconium in utero/during or after delivery
more severe disease if aspirate in utero
Soon after delivery if resp distress developed
WHY
1/3 of MAS infants need ventilation
10% of these cases die
Risk increases with GA
Significant morbidity in first few weeks of life
HOW
Thickening of pulmonary vessels
Primary or secondary PPHN
Aspirates mec stained fluid - thick mec=more complications
mec induces inflammatory cytokines
Surfactant dysfunction + deficiency
displace surfactant, damage T2 pneumocytes
chemical pneumonitis
interferes with alveolar gas exchange
RDS
obstructs airways
pneumothorax
Lung Infection
In utero Hypoxia + acidosis
vagal response - Increased peristalsis + relaxed anal sphincter
Meconium passage
Foetal gasping - more likely to swallow mec
Chronic in utero stress