MECONIUM ASPIRATION SYNDROME

Moderator -Dr Binod

Presenter -Int Lalit Karki

Definition • Meconium aspiration syndrome ( MAS ) is a respiratory distress of an

infant born through meconium stained amniotic fluid

• Meconium found below vocal cord

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

• 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.

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

Meconium• Sterile, thick, black-green, odorless material• Results from the accumulation of debris in the fetal intestine during the third month

of gestationComponents:• 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

Pathophysiology of meconium aspiration.

Wiswell T, Bent RC. Meconium staining and the meconium aspiration syndrome: unresolvedissues. Pediatr Clin NorthAm 1993;40:955.

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.

CLINICAL FEATURESHistory• 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

• 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.

Differential diagnosis• Perinatal Asphyxia

• Bacterial Pneumonia

• Respiratory Distress Syndrome

• Transient Tachypnea Of Newborn

• Congenital Heart Disease

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

Air trapping and hyperexpansion due to airway

obstruction

Diffuse, asymmetric patchy infiltrates

Areas of consolidationHyperinflation

Atelectasis

Diffuse chemical pneumonitis

Delivery room management Anticipate the worst….

Be prepared…

MANAGEMENT OF INFANTS DELIVERED THROUGH MECONIUM STAINED FLUID.Initial assessmentWhether 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 ofthe consistency of the meconium.

2. If respiratory distress develops or the infant becomes depressed intubate under direct laryngoscopy and intra tracheal suctioning.

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 HgContinuous suction is applied as the tube is being withdrawn; the procedure is repeated until the trachea is cleared or resuscitation needs to be initiated.

5. Avoid positive pressure ventilation, if possible, until tracheal suctioning isaccomplished.

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.

MANAGEMENT OF MASA . 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.

B. Care for neonate with MAS1.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.

4. Circulatory support with normal saline or packed red blood cells in patients with marginal oxygenation. Maintain a hemoglobin concentrationabove 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

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.

D. Assisted ventilation1. 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).

• Ventilator setting:oPIP:25-30 cm H2OoPEEP:0-3 cm H2OoRate:40-60/minoI: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.

E. Medications1. 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.

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

Complications1 . 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'soverall hypoxemia and to exclude congenital heart disease as the etiology• Treatment: inhaled nitric oxide (iNO) reduces the need for ECMO.

3. Pulmonary sequelae:• Approximately 5% of survivors require supplemental oxygen at 1

month,• Increased functional residual capacity,• Airway reactivity, and• Higher incidence of pneumonia.

PREVENTION OF MASA. 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

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