MAS

1. MECONIUM ASPIRATION SYNDROME
Moderator
-Dr Binod
Presenter
-Int Lalit Karki

2. Definition
• Meconium aspiration syndrome ( MAS ) is a respiratory distress of an
infant born through meconium stained amniotic fluid
• Meconium found below vocal cord

3. Introduction
• Meconium-stained amniotic fluid found in 10-15% of births- term or
post term infants
• Meconium aspiration syndrome(MAS) develops in:
5% of such infants;
30% require mechanical ventilation and
3-5% die
• May be depressed and require resuscitation at birth
• Infants are at increased risk of persistent pulmonary hypertension

4. • Acute or chronic hypoxia and/or infection can result in the passage of
meconium in utero.
• In this setting, gasping by the fetus or newly born infant can
cause aspiration of amniotic fluid contaminated by meconium.

5. Risk factors for MAS
• Gestational hypertension
• Gestational DM
• Maternal heavy cigarette smoking
• Maternal chronic respiratory or cardiovascular disease
• Post date pregnancy/Post maturity
• Pre-eclampsia/eclampsia
• Oligohydromnions
• IUGR
• Abnormal fetal HR pattern

6. Meconium
• Sterile, thick, black-green, odorless material
• Results from the accumulation of debris in the fetal intestine during the
third month of gestation
Components:
• Water (72%-80%),
• Desquamated cells from the intestine and skin,
• Gastrointestinal mucin, lanugo hair,
• Fatty material from the vernix caseosa, amniotic fluid, intestinal secretions,
• Blood group-specific glycoproteins, bile, and drug metabolites.
Description
• Light – amniotic fluid thinly stained, watery
• Moderate – opaque without particles
• Thick – pea soup particles

7. Pathophysiology of meconium aspiration.
Wiswell T, Bent RC. Meconium staining and the meconium aspiration syndrome: unresolved
issues. Pediatr Clin NorthAm 1993;40:955.

8. Classification of respiratory disease.
 Mild MAS is a disease requiring <40% oxygen for <48 hours.
 Moderate MAS is a disease requiring >40% oxygen for >48 hours without air leak.
 Severe MAS is a disease requiring assisted ventilation for >48 hours, often associated with PPHN.
Sequlae. In utero passage of meconium in
 Term infants:
• an increased risk of perinatal and neonatal mortality,
• severe acidemia,
• need for caesarean section delivery,
• need for intensive care and oxygen administration, and
• adverse neurologic outcome.
 Preterm infants
• Have similar adverse effects, as well as
• An increased incidence of severe intraventricular hemorrhage, cystic periventricular
leukomalacia, and cerebral palsy.

9. CLINICAL FEATURES
History
• Infant with MAS must have a history of MSAF
• Often are term or post-term
• IUGR
• Many are depressed at birth
Physical Examination
• Evidence of postmaturity ; peeling skin, long fingernails, reduced vernix
• Vernix, umbilical cord and nails may be meconium-stained, depending how
long the infant has been exposed in utero
Generally
• nails stained after 6 hrs
• vernix after 12-14 hrs
• umbilical cord staining thick 15 min, thin 1 hour

10. • Respiratory distress with marked tachypnea and cyanosis within the first
hours.
• Use of accessory muscles of respiration (ICR, SCR and abdominal breathing)
, grunting and nasal flaring.
• Chest : appears barrel shape with increase AP diameter due to over
inflation
• Auscultation : rhonchi immmediately after birth
• Sign of cerebral irritation from cerebral edema or hypoxia : jitteriness,
seizures
• Some patient are asymptomatic at birth and develop worsening signs of
respiratory distress as the meconium moves from large airways into the
lower tracheobronchial tree.

11. Differential diagnosis
• Perinatal Asphyxia
• Bacterial Pneumonia
• Respiratory Distress Syndrome
• Transient Tachypnea Of Newborn
• Congenital Heart Disease

12. Investigations
• Chest radiograph
- hyperinflated lung and flatten diapghram
- B/L diffuse grossly irregular patchy infiltrates
- Pneumothorax and pneumomediastinum
- Small pleural effusion
- No air bronchogram
• Arterial blood gas (Acid-base status)
- VQ mismatch
-Acidosis
- Hypoxia
- Hypercarbia
• Blood glucose and Calcium levels

13. Air trapping and
hyperexpansion due to airway
obstruction
Diffuse, asymmetric patchy
infiltrates
Areas of consolidation
Hyperinflation

14. Atelectasis

15. Diffuse chemical pneumonitis

16. Delivery room management
Anticipate the worst….
Be prepared…

17. MANAGEMENT OF INFANTS DELIVERED THROUGH
MECONIUM STAINED FLUID.
Initial assessment
Whether the infant is vigorous, demonstrated by
• heart rate > 100 beats per minute,
• spontaneous respirations, and
• good tone (spontaneous movement or some degree of flexion).
1. If the infant appears vigorous, provide routine care regardless of
the consistency of the meconium.
2. If respiratory distress develops or the infant becomes depressed intubate
under direct laryngoscopy and intra tracheal suctioning.

18. Suctioning technique for the non vigorous
meconium-stained infant
1.Place on a radiant warmer and give free-flow oxygen.
2. Delay drying, stimulating, and gastric suctioning.
3. Intubate the trachea under direct laryngoscopy, preferably
before inspiratory efforts have been initiated.
4. After intubation, meconium aspirator is attached and
connected to wall suction at a pressure of 80 to 100mm Hg
Continuous suction is applied as the tube is being
withdrawn; the procedure is repeated until the trachea is
cleared or resuscitation needs to be initiated.

19. 5. Avoid positive pressure ventilation, if possible, until tracheal suctioning is
accomplished.
6.Postpone emptying gastric contents until the infant has stabilized.
Complications of intubation include bleeding, laryngospasm, stridor,
apnea,and cyanosis.
This procedure should be accomplished rapidly, and ventilation with oxygen
should be initiated before significant bradycardia occurs.

20. MANAGEMENT OF MAS
A . Observation.
Depressed at birth and have had meconium suctioned from the
trachea are at risk for meconium aspiration pneumonia
1 . A chest radiograph
2. Monitoring of oxygen saturation : severity of the infant's
condition and avoids hypoxemia.

21. B. Care for neonate with MAS
1.Maintained in a neutral thermal environment and minimimum tactile stimulation
2. Restrict fluid as much as possible to prevent cerebral and pulmonary edema.
3. Specific therapy for hypotension and poor cardiac output, including cardiotonic
medications such as dopamine.

22. 4. Circulatory support with normal saline or packed red blood cells in
patients with marginal oxygenation. Maintain a hemoglobin concentration
above 15 g (hematocrit above 40%)
5. Monitor renal function continuously
6. Avoid chest physiotherapy
7. Airway and oral suctioning may be required to facilitate airway clearance

23. C. Oxygen therapy.
• Management of hypoxemia should be accomplished by
increasing the inspired oxygen concentration and by
monitoring blood gases and pH.
• Provide sufficient oxygen to avoid ongoing pulmonary
vasoconstriction and development of PPHN.

24. D. Assisted ventilation
1. Free flow of oxygen
2 . Continuous positive airway pressure (CPAP). If Fi02
requirements exceed 40%, a trial of CPAP may be considered.
Caution if hyperinflation is apparent clinically or
radiographically.
2. Mechanical ventilation. Mechanical ventilation is indicated
for excessive:
• carbon dioxide retention (PaC02 >60 mm Hg) or
• for persistent hypoxemia(Pa02 <50 mm Hg).

25. • Ventilator setting:
oPIP:25-30 cm H2O
oPEEP:0-3 cm H2O
oRate:40-60/min
oI:E ratio: 1:3 (IT 0.2 to 0.3 sec)
• High-frequency ventilation with jet or oscillatory ventilators:
effective in infants with severe MAS who fail to improve with
conventional ventilation, air-leak syndromes.
3 .Extracorporeal membrane oxygenation (ECMO) may be required for
infants with refractory respiratory failure.

26. E. Medications
1. Antibiotics.
• Although few infants with MAS have documented infections, the use of
broad-spectrum antibiotics (e.g., ampicillin and gentamicin);usually
indicated in infants with infiltrate seen on chest radiograph.
• Obtain blood cultures: to identify bacterial disease,to determine length of
antibiotic course.
2. Surfactant.
• Surfactant treatment of MAS may improve oxygenation and reduce
pulmonary complications and the need for ECMO.
• Indicated in infants whose clinical status continues to deteriorate and who
require escalating support, surfactant administration may be helpful.

27. 3. Corticosteroids.
• To reduce inflammation induced by meconium and minimize
prostaglandin-mediated pulmonary vasoconstriction.
4. Sedatives.
• The use of sedation and muscle relaxation warranted in infants who
require mechanical ventilation
5 . Inhaled nitric oxide
• MAS with pulmonary hypertension
• In setting without iNO, sildenafil reduced PVR and improves
oxygenation and decrease mortality

28. Complications
1 . Air leak. Pneumothorax or pneumomediastinum :15% to 33% of patients
with MAS. Air leaks occur more frequently with mechanical ventilation,
especially in the setting of air trapping.
2. PPHN
• One-third of cases
• Depending on the extent of hypoxemia, echocardiography should be
performed to ascertain:
the degree to which the right-to-left shunting is contributing to the infant's
overall hypoxemia and
 to exclude congenital heart disease as the etiology
• Treatment: inhaled nitric oxide (iNO) reduces the need for ECMO.

29. 3. Pulmonary sequelae:
• Approximately 5% of survivors require supplemental oxygen at 1
month,
• Increased functional residual capacity,
• Airway reactivity, and
• Higher incidence of pneumonia.

30. PREVENTION OF MAS
A. Prevention of passage of meconium in utero. Mothers at risk for
uteroplacental insufficiency and,
These women should be carefully monitored during pregnancy.
B. Amnioinfusion.
• Does not reduce neonatal morbidity related to meconium aspiration,
• Although the technique effectively treats repetitive variable fetal
heart rate decelerations by relieving umbilical cord compression in
labor.
C. Timing and mode of delivery.
• In pregnancies that continue past the due date, induction as early as
41 weeks may help prevent MAS by avoiding passage of meconium

31. Reference:
• Manual of Neonatal Care,7th ed, john P. Cloherty. MD,Eric C.
Eichenwald, MD,Anne R. Hansen, MD, MPH,Ann R Stark, MD
• Nelson textbook of Pediatrics,20th ed