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Meconium Aspiration Syndrome

Meconium Aspiration Syndrome. Edited May 2005. Pulmonary Vascular Resistance. Pulmonary Venous Return. LA Pressure. Ventilation. Foramen Ovale Closes. L --> R ductus arteriosus shunt. PO 2. RA Pressure. IVC Return. Ductus Venosus Closes. Remove Placenta.

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Meconium Aspiration Syndrome

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  1. Meconium Aspiration Syndrome Edited May 2005

  2. Pulmonary Vascular Resistance • Pulmonary Venous Return • LA Pressure Ventilation Foramen Ovale Closes L --> R ductus arteriosus shunt • PO2 • RA Pressure • IVC Return Ductus Venosus Closes Remove Placenta • Umbilical Venous Return • Systemic Vascular Resistance

  3. What is meconium aspiration? • Meconium is the first intestinal discharge of the newborn • Epithelial cells, fetal hair, mucus, bile • Intrauterine stress may cause in utero passage of meconium • Aspirated by the fetus when fetal gasping or deep breathing occurs stimulated by hypoxia and hypercarbia • Warning sign of fetal distress

  4. Meconium: The Stats • Frequency of Mec stained amniotic fluid = 10-25% • OF MEC stained infants: • 30 % depressed at birth • 10 % meconium aspiration syndrome (range 2-36 %) • OF infants with MEC aspiration syndrome • 17 % deliver through thin meconium (range 7-35 %) • 35 % need mechanical ventilation (range 25-60 %) • 12 % die (range 5-37 %)

  5. OHSU Experience: Inborn + Transfers MAS = Meconium aspiration syndrome as primary pulmonary diagnosis No pulmonary hypoplasia or major congenital anomalies MAS+ vent = ventilated with pulmonary diagnosis of MAS or PPHN ECMO = MAS infants transferred for ECMO Died : * 1 infant in each of the years died with a diagnosis of severe HIE

  6. Risk Factors for Meconium Passage • Postterm pregnancy • Preeclampsia-eclampsia • Maternal hypertension • Maternal diabetes mellitus • Abnormal fetal heart rate • IUGR • Abnormal biophysical profile • Oligohydramnios • Maternal heavy smoking

  7. Meconium in Amniotic Fluid Intrapartum suctioning of mouth, nose, pharynx Infant Depressed Infant Active Intubate and suction trachea Observe Other resuscitation as indicated

  8. Meconium Aspiration SyndromePathophysiology • Airway obstruction of large and small airways • Inflammation and edema • Protein leak • Inflammatory Mediators • Direct toxicity of meconium constituents = chemical pneumonitis • Surfactant dysfunction or inactivation • Effects of in utero hypoxemia and acidosis • Altered pulmonary vasoreactivity (PPHN)

  9. Meconium Aspiration SyndromeDiagnosis • Known exposure to meconium stained amniotic fluid • Respiratory symptoms not explained by other cause • R/O pneumonia, RDS, spontaneous air leak • CXR changes - diffuse, patchy infiltrates, consolidation, atelectasis, air leaks, hyperinflation

  10. Meconium Aspiration SyndromeTreatment • Ventilation strategies • Avoid air leak, check CXR with acute deterioration • Prevent pulmonary hypertension - generous O2 • HFOV if unable to maintain on conventional vent • Steroids (no human data, controversial) • ROS, Antibiotics (ampicillin, gentamicin) • Surfactant • Inhaled Nitric Oxide • ECMO

  11. Other Things to Watch For • Hypoxia • Acidosis • Hypoglycemia • Hypocalcemia • End-organ damage due to perinatal asphyxia

  12. Meconium Aspiration SyndromeOutcome High incidence long term pulmonary problems At 6 months - 23% MAS with regular bronchodilator therapy* FRC was higher in symptomatic infants IPPV and O2 were not predictors of problems Increased risk of poor neurologic outcome due to perinatal insult - seizures, CP, mental retardation *Yuksel et al. Pediatric Pulmonology 16:358, 1993

  13. Meconium Aspiration SyndromeSurfactant Treatment Methods • < 6 hours old with MAS • 20 infants randomized to receive 150 mg/kg surfactant by 20 minute infusion, q6h x4 doses maximum • On ventilator - FiO2 > 50%, MAP > 7, a:A PO2 < 0.22 • Endpoint = improvement in OI and a:A PO2 • No difference in groups Findlay et al. Pediatrics 97 (1): 48, 1996.

  14. Meconium Aspiration SyndromeSurfactant Treatment Results • No infant received more than 3 doses • Significant improvement in OI, MAP, FiO2 within 3-6 hours after 2nd dose of surfactant • Significant improvement in a:A PO2 within 1 hour of 1st dose of surfactant Findlay et al. Pediatrics 97 (1): 48, 1996.

  15. Meconium Aspiration SyndromeSurfactant Treatment Findlay et al. Pediatrics 97 (1): 48, 1996.

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