Meconium Happens:Meconium Aspiration Syndrome

Meconium Happens:Meconium Aspiration Syndrome

John Salyer RRT-NPS, FAARC, MBA

Director Respiratory Therapy

Seattle Children’s Hospital and Research Institute

The CulpritThe Culprit

What is meconium aspiration?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 25-60 %)

12 % die (range 5-37 %)

Meconium: The StatsMeconium: The Stats

PO2

L --> R ductus arteriosus

shunt

Ventilation

Remove Placenta

Ductus Venosus Closes

Systemic Vascular Resistance

ß Umbilical Venous Return

ß IVC Return

ß RA Pressure

Ý Pulmonary Venous Return

Ý 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• 40-60 breaths/min

2. Lowest PIP sufficient for chest excursion• Start at 16/5 and institute HFOV for

PIP>25• target VT 4-6 mL/kg BW• ECLS for mPaw>14• Heavy sedation for gas trapping

3. Short Inspiratory Times• 0.3-0.5 s• Longer Expiratory Times and lower

PEEP for gas trapping4. Nitric Oxide works well in this

population

Blood Gases

1. No pulmonary hypertension• pCO2 levels 40-50• pH > 7.30• Pa02 70-80

2. Pulmonary hypertension• pCO2 levels 30-35• pH > 7.35• Pa02 80-100

Airflow Scalars in a patient with MAS

OHSU Experience: Inborn + TransfersOHSU Experience: Inborn + Transfers

# Mecpassed

DRintub

MAS MAS+ vent

ECMO Died

1992-94 146 88 44 28 4 3*1995-97 154 92 39 25 1 1*

Total 300 180 83 53 5 4

MAS = Meconium aspiration syndrome as primary pulmonary diagnosisNo pulmonary hypoplasia or major congenital anomalies

MAS+ vent = ventilated with pulmonary diagnosis of MAS or PPHNECMO = MAS infants transferred for ECMO Died : * 1 infant in each of the years died with a diagnosis of severe HIE

Risk Factors for Meconium PassageRisk 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 ActiveInfant Depressed

Intrapartum suctioning of mouth, nose, pharynx

Intubate and suction trachea

Other resuscitation as indicated

Observe

Meconium in Amniotic Fluid

Meconium Aspiration SyndromePathophysiology

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)

Meconium Aspiration SyndromeDiagnosis

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

Meconium Aspiration SyndromeTreatment

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

Other Things to Watch ForOther Things to Watch For

Hypoxia

Acidosis

Hypoglycemia

Hypocalcemia

End-organ damage due to perinatal

asphyxia

Fox WW,. Pediatrics 1975; 56:214–217.

Meconium Aspiration SyndromeSurfactant Treatment

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.

Meconium Aspiration SyndromeSurfactant Treatment

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.

Control Surf P valueAir leak 5 0 0.024ECMO 6 1 0.037Days MV 11 (1) 8 (1) 0.047Days O2 20 (3) 13 (1) 0.031LOS (days) 24 (2) 16 (1) 0.003D/C on O2 8 6 NSMortality (< 28 d) 0 0 NS

Meconium Aspiration SyndromeSurfactant Treatment

Meconium Aspiration SyndromeSurfactant Treatment

Findlay et al. Pediatrics 97 (1): 48, 1996.

Meconium Aspiration SyndromeOutcome

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