Meconium aspiration syndrome (MAS) is a condition that can occur in newborn babies when they inhale a mixture of meconium and amniotic fluid into their lungs during or before birth.
Meconium is a sticky substance in the intestines of all fetuses. It typically passes during the first few days after birth. However, it may pass early when a fetus is distressed, resulting in serious problems, including respiratory distress and low Apgar scores.
This case study will focus on an infant who presented with meconium aspiration syndrome. We’ll also explore the diagnosis and treatment of this condition.
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Meconium Aspiration Syndrome Clinical Scenario
You are called to the OR for the post-term delivery of a 29-years-old primigravida with no known health conditions. She does not drink or smoke and has received appropriate prenatal care. The doctor induced the mother because her labor was not progressing naturally. In addition, the fetus was showing signs of distress via decelerations. The fetus has shown no sign of a health disorder on the ultrasounds or laboratory work completed during the mother’s pregnancy.
What is the Diagnosis?
Based on the information given, the infant likely has meconium aspiration syndrome. The key findings are that the baby is being delivered post-term and has shown signs of being stressed.
Fetal stress and hypoxemia during utero are often associated with increased peristalsis and a relaxed anal sphincter. These two factors may cause the fetus to pass its first bowel movement (i.e., meconium).
The presence of meconium in amniotic fluid poses a problem if the fetus aspirates it. Fetuses typically exhibit slow, shallow inspiratory efforts, and their glottis remains closed while in utero.
However, a fetus that is hypoxic or in distress may begin gasping. These deeper inhalations can cause the amniotic fluid and meconium to be pushed passed the glottis and into the airways.
This poses a problem as meconium is thick, sticky, and contains bacteria from the gastrointestinal tract. This causes respiratory complications in the infant post-delivery.
How to Determine When Meconium Aspiration Syndrome is Present
You can try to predict if the infant will have MAS or not by listening for the physician to call out “fluid stained” or “fluid clear” during delivery.
When a physician says “fluid stained,” it means the mom’s amniotic fluid had color, and meconium was present. If the fluid is stained, it doesn’t always mean the infant has aspirated meconium. However, this requires you to monitor the infant closely for signs of MAS.
Primary Risk Factor for MAS
MAS is typically only present in infants that are born at 36 weeks gestation or older. This is the developmental stage in which the anal sphincter has enough tone to pass meconium. Infants that are born post-term (i.e., after 42 weeks) are at the highest risk for MAS.
Complications of Meconium Aspiration Syndrome
MAS can cause a variety of respiratory complications in infants, including:
- Chemical pneumonitis: Chemical pneumonitis is characterized by atelectasis and increased production of bronchial secretions. It is caused by the lung’s inflammatory response to the presence of meconium. In addition, meconium contains bacteria that can stimulate a continued inflammatory response in the lungs after birth.
- Respiratory distress syndrome (RDS): The production of surfactant may be reduced in infants with MAS, leading to RDS.
- Upper airway obstruction: Meconium is a thick, sticky substance that can cause an obstruction in the upper airway.
- Alveolar hyperinflation, pneumomediastinum, and pneumothorax: If meconium gets stuck in the lower airways, this may cause a partial obstruction, resulting in a ball-valve effect. This means the infant is able to effectively inspire air but not exhale it completely.
- Atelectasis: Meconium can cause a complete obstruction in the airways, resulting in alveolar collapse.
MAS Scenario: Continued
The doctor is performing a C-section and announces that the amniotic fluid is stained; therefore, MAS is suspected. What findings would you expect?
- Nasal flaring: This is a sign of respiratory distress and increased work of breathing.
- Central cyanosis: This is a sign of hypoxia.
- Expiratory grunting: This is a natural maneuver by the infant to create intrinsic PEEP and open up their airways.
- Retractions: This is a sign of respiratory distress.
- See-saw breathing: This is a sign of respiratory distress.
- Stained skin: The newborn may present with brown or yellow staining from the meconium.
- Increased anterior-posterior diameter: This is a sign of air trapping.
- Wheezing or crackles during auscultation: These are signs of airway obstruction (e.g., with fluid).
- Signs of post-term birth: Some signs of a post-term birth include the presence of nails and wrinkles on the skin.
Patchy, irregular densities are common radiological findings in patients with MAS. However, if air trapping is present, their chest x-ray may show other findings, such as:
- Increased hyperlucency
Moments After Birth
If an infant is born with no central cyanosis, stained skin, and no respiratory efforts, what should you avoid in the first moments after birth?
In this case, you should avoid immediately applying positive pressure ventilation (PPV) or stimulating the infant enough to make them cry or gasp. That is because these actions can cause the meconium in the upper airways to move further down into the lower airways.
Therefore, you should first perform airway suctioning to clear meconium from the upper airway.
Treatment for MAS
After suctioning a mild amount of thick, sticky, and stained secretions, the infant is now breathing independently. It has an APGAR of 7 but shows signs of hypoxia, tachypnea, tachycardia, nasal flaring, and grunting. What would you recommend?
You should recommend the application of nasal CPAP with oxygen. Since you have already suctioned the newborn, you can now apply positive pressure to assist with breathing.
Nasal CPAP is indicated in this case because it can open their airways and help push out some of the fluid that is trapped in the lungs.
Furthermore, grunting is a sign that a newborn is trying to create intrinsic PEEP. The application of CPAP is indicated for infants with signs of respiratory insufficiency.
Other Treatments Methods
- Bronchopulmonary hygiene: This can help remove fluid from the infant’s lungs.
- Mechanical ventilation: This is only implemented if the infant exhibits signs of respiratory failure. Infants with MAS should be placed on a ventilator mode that can provide a long expiratory time to prevent air-trapping.
- Antibiotics: These are administered to prevent or treat infections caused by MAS.
- Surfactant replacement therapy: This is administered to reduce the surface tension of the infant’s lungs and make up for the lack of production.
- Nitric oxide: This is indicated if the infant develops persistent pulmonary hypertension.
- ECMO: This is used in severe cases if the infant does not improve after receiving all other treatment options.
Meconium aspiration syndrome (MAS) is a serious condition that requires immediate medical attention. This is an essential topic for respiratory therapists, especially those specializing in neonatal and pediatric care.
Therefore, RTs must recognize the signs and symptoms of MAS to perform a diagnosis and provide quick and appropriate intervention.
Hopefully, this case study has helped provide you with a better understanding of this condition. Thanks for reading, and, as always, breathe easy, my friend!
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
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- Raju, U., et al. “Meconium Aspiration Syndrome: An Insight.” National Library of Medicine, Med J Armed Forces India, Apr. 2010, www.ncbi.nlm.nih.gov/pmc/articles/PMC4920933.