Meconium aspiration syndrome

Abstract 

Meconium aspiration syndrome (MAS) is a rare condition affecting infants who inhale or aspirate meconium-stained liquor during or after labour. It is a serious disease with complications of neonatal respiratory distress, and can lead to the death of infants if it is not detected early or is left untreated.

Hypoxia, hypercarbia and chorioamnionitis predispose infants to this condition, and often they are associated with abnormal patterns of heart rate in the fetus. Hypoxia and fetal hypercarbia stimulate gasping. Gasping movements of infants can cause meconium to be taken into the bronchial tree before or during labour, leading to MAS. Fetal heart rate changes can be an indication of MAS. The arterial pH in the cord is lower in babies who show heart rate abnormalities with meconium-stained fluid, indicating fetal hypoxia.

The complications of meconium aspiration include airway obstruction, chemical pneumonitis and surfactant dysfunction. This may lead to further hypoxia in infants. Several efforts in prevention, such as amnioinfusion, sedation and aspiration of oropharynx before the nasopharynx, have met with little success.

Treatment of MAS is by adequate oxygenation and meticulous homeostasis of the blood gases, haematological and biochemical indices. ECG, chest radiography and microbiology screening are important for confirmation and treatment. Ventilation with oxygen, surfactants, inhaled nitric oxide, corticosteroids and extracorporeal membranous oxygenation may potentially accelerate the recovery of MAS. Many recover, but several neonates die or develop serious long-term neurological or respiratory complications. Recent guidelines from the UK National Institute of Health and Clinical Excellence provide information on the care of women in labour with meconium-stained amniotic fluid.

Keywords: meconium aspiration syndrome, neonatal respiratory distress, hypoxia, asphyxia, extracorporeal membranous oxygenation, persistent pulmonary hypertension of newborn