Meconium aspiration syndrome

1. MECONIUM ASPIRATION
SYNDROME

2. Meconium aspiration occurs due to
combination of meconium stained amniotic
fluid and gasping by the fetus or newly born.

3. EPIDEMIOLOGY
 Meconium stained amniotic fluid complicates approximately 10% to 15% of
deliveries
 The incidence of MSAF in preterm is very low.
 Most babies with MSAF are 37 weeks or older and many meconium stained
infants are post mature or SGA.
 Incidence has decreased in developed coumtries due to better perinatal care
but remains high in developing countries.

4. MECONIUM
 Sterile, thick, black-green, odorless material that results from accumulation
of debries in fetal intestine stating in 3rd month of gestation

5. COMPOSITION OF MECONIUM
 Water
 Desquamated cells
 GI mucin
 Lanugo hair cells
 Bile
 Amniotic fluid

6. CAUSES
Passage of meconium in utero
 Normally passage of meconium from fetus to amnion is prevented by lack of
peristalsis i.e low motilin levels, tonic contraction of Anal spincter.
 Post term fetus has high motilin levels.
 Vagal stimulation by chord or head compression or in utero fetal stress
causing relaxation of Anal spincter.

7. RISK FACTORS
 Maternal Hypertension
 Maternal DM
 Maternal heavy cigarette smoking
 Maternal chronic respiratory or cardiovascular disorder
 Post term pregnancy
 Pre-eclampsia/eclampsia
 Oligohydramnios
 IUGR
 Abnormal fetal HR pattern

8. PATHOPHYSIOLOGY

9. PATHOPHYSIOLOGY
Chemical pneumonitis
Surfactant inactivation
 When aspirated into lungs, meconium may stimulate release of cytokines and
vasoactive substances that result in cardiovascular and inflammatory response
in fetus and newborn .
 Meconium causes mechanical obstruction leading to atelectasis and ball valve
effect with resultant air trapping.
 Aspirated meconium inhibits surfactant function.
 Enzymatic and sterol component of meconium disrupts the surfactant
phospholipids and limit the ability of surfactant to to lower surface tension.

11. PATHOPHYSIOLOGY
Pulmonary hypertension
 Aspirated meconium leads to vasospasm,hypertrophy of pulmonary
vasculature and pulmonary hypertension
 About one-third infants with MAS develop persistant pulmonary hypertension
of newborn, which contribute to mortality associated with the syndrome,

12. SEVERITY
 MAS is considered mild in infants requiring <40% oxygen foe <48 hours and
moderate in infants requiring >40% oxygen for >48 hours without air leak.
 It is considered severe in infants who require assisted ventilation and/or CPAP
and is often associated with PPHN.

13. CLINICAL FEATURES
 Infants with MAS must have a history of MSAF.
 They often are term or post term.
 IUGR

15. CLINICAL FEATURES
Physical examination
 Evidence of post maturity:peeling skin, long fingernails etc.
 The vernix,umbilical chord and nails may be meconium stained,depending
upon how long the infant has been exposed in utero.

16. Meconium stained umbilical chord

17. DIAGNOSIS
 A chest radiograph may help determine those infants who are most likely to
develop respiratory distress.
 Significant number of asymptomatic infants will have an abnormal appearing
chest film.
 Classic findings are diffuse, asymmetric patchy infiltrates, areas of
consolidation, often worse on right and hyperventilation.
 Monitoring of oxygen saturation during this period aids assessment of the
severity of the infant`s condition and avoids hypoxemia.

18. PREVENTION OF MAS
Prevention of passage of meconium in utero
Amnioinfusion
Timing and Mode of delivery
 Womens at risk which includes those with eclampsia, preeclampsia,
hypertensive, IUGR should be carefully monitored during pregnancy.
 Associated with improvement in perinatal outcome.
 It is not clear whether the benefits are due to dilution of meconium or relief
of oligohydramnios.
 Induction as early as 41 weeks can prevent MAS.
 Mode of delivery does not affect the risk of aspiration.

19. MANAGEMENT OF INFANTS DELIVERED
THROUGH MECONIUM STAINED FLUID
 Oropharyngeal and nasopharyngeal suctioning on perineum and routine
tracheal intubation and aspiration of meconium in vigorous infants are not
effective in preventing MAS.
 Although it was earlkier recommended in nonvigorous infants.
 According to 2015 Neonatal Resuscitation Guidelines, emphasis should be
placed on appropriate interventions to support ventilation and oxygenation.
 If an infant does not improve with intubation and positive-pressure ventilation
trachea should be suctioned using a suction catheter inserted through the ET
tube or directly suctioned through the tube using meconium aspirator.
 Recommended suction pressure should be less than 80 to 100 mmHg.

20. MANAGEMENT OF MAS
 A. OBSERVATION
 1. chest x-ray
 2. monitoring of oxygen saturation
 B. CARE FOR NEONATE WITH MAS
 1. infant should be maintained in neutral thermal environment.
 2. blood glucose and calcium levels should be assessed and managed if
necessary.
 3. therapy for hypotension and poor cardiac output, including cardiotonic
medications such as dopamine.
 4.circulatory support with NS or packed RBC in patients with marginal
oxygenation, in infants with substantial oxygenation and ventilator requirements
we maintain Hb concentration above 15g.
 5. monitor renal functions.

21.  C. OXYGEN THERAPY
 management of hypoxemia should be accomplished by increasing the
inspired oxygen concentration and by monitoring blood gases and pH.
 D. ASSISTED VENTILATION
 1. CPAP – if FiO2 requirement exceeds 0.40.
 2. MECHANICAL VENTILATION - indicated for excessive CO2 retention
(PaCO2 >60 mmhg) or for persistant hypoxemia (PaO2 <50 mmhg) .
 peak inspiratory pressure should be limited to pressures resulting in
gentle chest movement and tidal volume 5 to 6 ml/kg; PEEP should depend on
individual`s response.adequate expiratory time should be permitted to
prevent air trapping behind partly obstructed airways.
 useful starting points are inspiratory time of 0.4 seconds at a rate of 30 to
40 breths per minute.
 3. INHALED NITRIC OXIDE AND EXTRACORPOREAL MEMBRANE
OXYGENATION- in refractory respiratory failure

22.  E. MEDICATIONS
 1. Antibiotics
 use of broad spectrum antibiotics (e.g. ampicillin and gentamycin ) is usually indicated in
infants when an infiltrate is seen on chest radioghaph.
 blood cultures should be obtained to identify the bacterial disease, if present and to
determine duration of antibiotic course.
 2. Surfactant
 surfactant replacement improves oxygenation and reduces need for EMCO and is
recommended by committee on Fetus and Newborn of the American Academy of Pediatrics.
 BAL with dilute surfactant might be beneficial.
 3. Corticosteroids
 not recommended routinely.
 this approach has been proposed to minimize prostaglandin-mediated pulmonary
vasoconstriction.
 4. Sedatives
 in infants who require mechanical ventilation.
 5.Antioxidants
 N-acetylcystein and recombinant human superoxide dismutase to mitigate reactive oxygen
species(ROS) –induced lung injuryin MAS.

23. COMPLICATIONS
 1. AIR LEAK
 pneumothorax or pneumomediastinum occurs in approximately 15% to 33% of patients with
MAS.
 occurs more commonly with mechanical ventilation, especially in setting of air trapping
 2. PPHN
 seen in approximately one-third of cases and contributes to mortality associated with this
syndrome.
 depending on the extent of hypoxemia, echocardiography should be performed to
ascertain the degree to which the right and left shunt is contributing to infant`s overall
hypoxemia and exclude congenital heart disease.
 3. Pulmonary sequelae
 approximately 5% of survivors require supplemental oxygen at 1 month and a substantial
proportion may have an abnormal pulmonary function including increased functional residual
capacity and a higher incidence of pneumonia.

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