Meconium aspiration

Question 1

Define meconium aspiration syndrome (MAS).

Answer 1

Presence of mecinium in the trachea of a newborn

Question 2

Which group is meconium aspiration uncommon in?

Answer 2

Preterm infants

Question 3

What are the risk factors for meconium aspiration?

Answer 3

Greater gestational age - affecting ~35% of deliveries > 42 weeks.

Maternal: history of hypertension, pre-eclampsia, chorioamnionitis, smoking or substance abuse.

Fetal distress - stress may cause them to pass meconium e.g. chorioamnionitis, oligohydramnios

Thick meconium - more likely to cause MAS rather than thin

Asphyxiated infants - may start gasping and aspirate meconium before or at delivery

Question 4

Is MAS associated more commonly with vaginal or cesarean section delivery?

Answer 4

Babies born by caesarean section have a 1.89 times greater risk of MAS

Question 5

What is the pathophysiology of meconium aspiration?

Answer 5

Meconium is a lung irritant and results in both mechanical obstruction and a chemical pneumonitis, as well as predisposing to infection. In meconium aspiration the lungs are overinflated, accompanied by patches of collapse and consolidation.

Question 6

What % of infants pass meconium before birth?

Answer 6

8–20%

Question 7

List some possible signs and symptoms of MAS.

Answer 7

• tachypnoea
• barrel-shaped chest
• unequal chest expansion
• cyanosis

Question 8

What is the management of meconium aspiration?

Answer 8

Depending on whether mild/mod/severe may require the following:

1. Oxygen
   
   1. CPAP (moderate)- ABG monitored
   2. Mechanical ventilation (severe) +/- iNO
   3. ECMO (v severe)
2. Ampicillin+ gentamicin
3. Vasopressor - dobutamine or dopamine to maintain BP
4. Surfactant - beractant reduces progression to ECMO
   
   1. Endotracheal tube OR
   2. Lavage with diluted surfactant

Question 9

Does suction aspiration of the meconium from oropharynx immediately after birth reduce severity/incidence of meconium aspiration?

Answer 9

There is no evidence for this

Question 10

What are the complications associated with meconium aspiration?

Answer 10

• Respiratory distress
• Pneumothorax/pneumomediastinum
• Persistent pulmonary hypertension of the newborn
• Chronic lung disease
• Cerebral palsy/seizures due to hypoxaemia
• Mortality if severe