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
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 %)
OHSU Experience: Inborn + Transfers # Mec DR MAS MAS ECMO Died passed intub + vent 1992-94 146 88 44 28 4 3* 1995-97 154 92 39 25 1 1* Total 300 180 83 53 5 4MAS = Meconium aspiration syndrome as primary pulmonary diagnosis No pulmonary hypoplasia or major congenital anomaliesMAS+ vent = ventilated with pulmonary diagnosis of MAS or PPHNECMO = MAS infants transferred for ECMODied : * 1 infant in each of the years died with a diagnosis of severe HIE
Meconium in Amniotic Fluid Intrapartum suctioning of mouth, nose, pharynx Infant DepressedInfant Active Intubate and suctionObserve trachea Other resuscitation as indicated
Meconium Aspiration Syndrome Pathophysiology 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)
Meconium Aspiration Syndrome Diagnosis 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
Meconium Aspiration Syndrome Treatment 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
Other Things to Watch For Hypoxia Acidosis Hypoglycemia Hypocalcemia End-organ damage due to perinatal asphyxia
Meconium Aspiration Syndrome Outcome 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
Meconium Aspiration Syndrome Surfactant 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.
Meconium Aspiration Syndrome Surfactant 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.