Meconium Aspiration Syndrome
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Direct answer
Meconium aspiration syndrome is respiratory distress in a newborn who has inhaled meconium-stained liquor before, during or just after birth. It causes patchy lung inflammation, surfactant inactivation and airway obstruction, and it is most common in post-term or growth-restricted babies. Treatment is supportive, with oxygen, ventilation when needed, treatment of pulmonary hypertension and antibiotics until infection is excluded.
What you must remember
- Cause: fetal hypoxic stress triggers passage of meconium into the amniotic fluid, which the baby then inhales around birth.
- Risk groups: post-term pregnancy, growth restriction, fetal distress, breech presentation and prolonged or difficult labour.
- Pathology: chemical pneumonitis from meconium, surfactant inactivation, ball-valve airway obstruction causing air trapping, and persistent pulmonary hypertension.
- Clinical features: tachypnoea, grunting, cyanosis and a barrel-shaped chest, with yellow-green staining of skin, nails and cord.
- Radiograph: patchy, coarse, irregular opacities with hyperinflation and flattened diaphragms, and pneumothorax as a recognised complication.
- Intrapartum care: routine suction of the mouth before the shoulders are delivered is no longer recommended, and current NRP/AHA guidance no longer advises routine intubation and tracheal suction even in non-vigorous babies.
- Treatment: oxygen, gentle ventilation, inhaled nitric oxide for pulmonary hypertension, antibiotics until sepsis is excluded, and ECMO for refractory failure.
From the labour ward to the NICU
Management of meconium aspiration follows a sequence from the delivery room to the NICU, and the role of suction has changed over time. Students should know what is routine and what is now reserved for specific babies.
- Recognition: Meconium-stained liquor signals risk, so a trained attendant and a resuscitation team should be present at delivery.
- Delivery room: Routine oropharyngeal suction before delivery of the shoulders is not recommended. A non-vigorous baby gets the initial steps and positive-pressure ventilation if apnoeic or heart rate is below 100, with tracheal suction only if the airway is obstructed (older textbooks still advise routine intubation).
- Oxygenation: Oxygen is titrated to a target saturation, and the baby is watched for hypoxia and signs of pulmonary hypertension.
- Ventilation: Gentle ventilation limits air leak, and high-frequency ventilation or ECMO is considered for severe lung disease.
- Pulmonary hypertension: Inhaled nitric oxide treats hypoxic respiratory failure caused by persistent pulmonary hypertension of the newborn.
- Surfactant and sepsis: Surfactant lavage has been tried with variable evidence and is used selectively, while antibiotics are given until infection is excluded.
Surfactant is therefore an adjunct in selected severe cases rather than the first step. Oxygen and pulmonary hypertension care usually come first.
Where the exam tries to catch you
Meconium aspiration stems usually test the suction guidance, the X-ray pattern and the difference from RDS.
- Trap: suctioning the mouth of every stained baby before the shoulders are delivered. Correct: routine intrapartum oropharyngeal suction is no longer recommended, and current guidance does not advise routine tracheal suction even in non-vigorous infants.
- Trap: choosing surfactant as routine treatment for all meconium aspiration. Correct: surfactant lavage has variable evidence, so it is used selectively after oxygen and pulmonary hypertension care are addressed.
- Trap: confusing meconium aspiration with RDS because both cause grunting. Correct: meconium aspiration follows stained liquor in post-term or stressed babies with patchy opacities, whereas RDS affects preterm babies with ground-glass films.
Frequently asked questions
Why is meconium aspiration syndrome more common in post-term babies?
Meconium aspiration syndrome is more common in post-term babies because placental function declines with prolonged pregnancy, causing fetal stress that triggers meconium passage. Growth restriction and fetal hypoxia have a similar effect on meconium passage.
Is routine suction of meconium recommended at delivery?
Routine suction of meconium from the mouth before the shoulders are delivered is no longer recommended for meconium aspiration syndrome. Current NRP/AHA guidance does not advise routine tracheal intubation and suction even for non-vigorous babies, who instead receive ventilation if apnoeic or bradycardic, while older textbooks still describe it.
What is the typical X-ray finding in meconium aspiration syndrome?
The typical X-ray finding in meconium aspiration syndrome is patchy, coarse, irregular opacities with hyperinflation and flattened diaphragms. Pneumothorax is a recognised complication and may appear on the same film.
Is surfactant used in meconium aspiration syndrome?
Surfactant is used selectively in meconium aspiration syndrome, because surfactant lavage has shown variable benefit. Oxygen therapy, ventilatory support and treatment of pulmonary hypertension remain the main measures.