Meconium Aspiration Syndrome
July 13, 2009 · Leave a Comment
- Aspiration of meconium (the neonate’s first feces) into the lungs.
- Typically occur with the first breath or while the neonate is in utero.
- Thick, sticky, and greenish black substance; may be seen in the amniotic fluid after 34 weeks gestation.
- Asphyxia in utero leads to increased fetal peristalsis, relaxation of the anal sphincter, passage of meconium into the amniotic fluid, and reflex gasping of amniotic fluid into the lungs.
- Neonates with meconium aspiration syndrome (MAS) increase respiratory efforts to create greater negative intrathoractic pressures and improve air flow to the lungs.
- Hyperinflation, hypoxemia, and academia cause increased peripheral vascular resistance.
- Right-to-left shunting commonly follows.
- Meconium creates a ball-valve effect, trapping air in the alveolus and preventing adequate gas exchange.
- Chemical pneumonitis results, causing the alveolar walls and interstitial tissues to thicken, again preventing adequate gas exchange.
- Cardiac efficiency can be compromised from pulmonary hypertension.
- Commonly related to fetal distress during labor.
- Advance gestational age (greater than 40 weeks)
- Difficult delivery
- Fetal distress
- Intrauterine hypoxia
- Maternal diabetes
- Maternal hypertension
- Poor intrauterine growth
- Risk factors for MAS:
- Fetal hypoxia as indicated by altered fetal activity and heart rate.
- Dark greenish staining or streaking of the amniotic fluid noted on rupture of membranes.
- Obvious presence of meconium in the amniotic fluid
- Greenish staining of the neonate’s skin (if the meconium was passed long before delivery) or placenta.
- Signs of distress at delivery, such as the neonate appearing limp, an Apgar score below 6, pallor, cyanosis, and respiratory distress.
- Coarse crackles when auscultating the neonate’s lungs.
- Arterial blood gas analysis shows hypoxemia and decreased pH.
- Chest X-ray may show patches or streaks of meconium in the lungs, air trapping, or hyperinflation.
- Respiratory assistance via mechanical ventilation
- Maintenance of a neutral thermal environment
- Administration of surfactant and an antibiotic
- Extracorporeal membrane oxygenation (in severe cases).
- During labor, continuously monitor the fetus for signs and symptoms of distress.
- Immediately inspect any fluid passed with rupture of the membrane.
- Assist with immediate endotracheal suctioning before the first breaths, as indicated.
- Monitor lung status closely, including breath sounds and respiratory rate and character.
- Frequently assess the neonate’s vital signs.
- Administer treatment modalities, such as oxygen and respiratory support as ordered.
- Institute measures to maintain a neutral thermal environment.
- Provide the family with emotional support and guidance.