Meconium Happens: Meconium Aspiration Syndrome John Salyer RRT-NPS, FAARC, MBA Director Respiratory Therapy Seattle Children’s Hospital and Research Institute

The Culprit

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

Frequency of meconium stained amniotic fluid = 8-19 % Of MEC stained infants:  30 % depressed at birth  10 % meconium aspiration syndrome (range 5-33 %) Of infants with MEC aspiration syndrome  17 % deliver through thin meconium (range 7-35 %)  35 % need mechanical ventilation (range %)  12 % die (range 5-37 %) Meconium: The Stats

 PO 2 L --> R ductus arteriosus shunt Ventilation Remove Placenta Ductus Venosus Closes  Systemic Vascular Resistance  Umbilical Venous Return  IVC Return  RA Pressure  Pulmonary Venous Return  LA Pressure Foramen Ovale Closes  Pulmonary Vascular Resistance

Goldsmith JP. J Perinatology 2008:28;S49-S55

Ventilation Strategy for MAS Settings 1.Relatively Rapid Respiratory Rates breaths/min 2.Lowest PIP sufficient for chest excursion Start at 16/5 and institute HFOV for PIP>25 target V T 4-6 mL/kg BW ECLS for mPaw>14 Heavy sedation for gas trapping 3.Short Inspiratory Times s Longer Expiratory Times and lower PEEP for gas trapping 4.Nitric Oxide works well in this population Blood Gases 1.No pulmonary hypertension pCO 2 levels pH > 7.30 Pa Pulmonary hypertension pCO 2 levels pH > 7.35 Pa

Airflow Scalars in a patient with MAS

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

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

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

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

Fox WW,. Pediatrics 1975; 56: 214–217.

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 - FiO 2 > 50%, MAP > 7, a:A PO 2 < 0.22 Endpoint = improvement in OI and a:A PO 2 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, FiO 2 within 3-6 hours after 2 nd dose of surfactant Significant improvement in a:A PO 2 within 1 hour of 1 st dose of surfactant Findlay et al. Pediatrics 97 (1): 48, 1996.

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

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