Meconium aspiration syndrome

Dr Bob Klajo

Meconium

• Derived from Greek word mekoni meaning poppy juice or opium

• Viscous, dark green fecal material that accumulates in the fetal colon throughout gestation composed of intestinal epithelial cells, lanugo, mucus, and intestinal secretions such as bile

• Passage of meconium normally occurs within the first 24 to 48 hours after birth

• Passage of fetal meconium, resulting in meconium-stained amniotic fluid occurs in approximately 12 percent of all deliveries

Meconium Aspiration Syndrome — More Than Intrapartum Meconium Michael G. Ross, M.D., M.P.H.N Engl J Med 2005; 353:946-948 September 1, 2005

Risk factors• Gestational age

- 2% infants born before 37 weeks- 44% infants born at 44 weeks

• Intrauterine distress- placental insufficiency- maternal hypertension- preeclampsia- oligohydramnios- maternal drug abuse

Meconium staining of amniotic fluid and its association with fetal distress and gestational age S. N. Parida, I. C. Verma, S. Thomas and H. P. S. SachdevIndian Journal of Pediatrics Volume 47, Number 2, 141-143, DOI: 10.1007/BF02822881

Meconium aspiration vs meconium aspiration syndrome

• Meconium aspiration syndrome

- respiratory distress with radiological evidence of aspiration pneumonitis in the presence of meconium

• Meconium aspiration

- presence of meconium below the

vocal cords. - prelude to the

development of MAS

MNA Faridi, P Gupta, D Behl –

Indian pediatrics, 1994 - indianpediatrics.net

Pathophysiology

• Mechanical obstruction of the airways- Pneumothorax, pneumomediastinum, pneumopericardium

• Chemical pneumonitis- Primary or secondary persistent pulmonary hypertension of the newborn (PPHN)

• Surfactant inactivation- Diffuse atelectasis

Meconium Aspiration Syndrome – e-Medicine.netMelinda B Clark, MD, Assistant Professor of Pediatrics, Department of Pediatrics, Albany Medical College

Pathophysiology of meconium aspiration (adapted from Wiswell T, Bent RC. Meconium staining and the meconium aspiration syndrome. Pediatric Clinics of North

America.1993;40(5):955-981).

Symptoms

• Severe respiratory distress - Cyanosis- End-expiratory grunting- Alar flaring- Intercostal retractions- Tachypnea- Barrel chest in the presence of air trapping- Auscultated rales and rhonchi (in some cases)

Meconium Aspiration Syndrome – e-Medicine.netMelinda B Clark, MD, Assistant Professor of Pediatrics, Department of Pediatrics, Albany Medical College

Investigations• Arterial blood gases

- Metabolic acidosis complicated by respiratory acidosis • Serum electrolytes

- (SIADH) and acute renal failure• Full blood count

- Hemoglobin and hematocrit levels must be sufficient to ensure adequate oxygen-carrying capacity

• Echocardiogram- ensures normal cardiac structure and assesses cardiac function, as well as the severity of pulmonary hypertension and right-to-left shunting

Meconium Aspiration Syndrome – e-Medicine.netMelinda B Clark, MD, Assistant Professor of Pediatrics, Department of Pediatrics, Albany Medical College

Chest X-rayPneumomediastinum Diffuse chemical

pneumonitisAcute atelectasis

eMedicine - Meconium Aspiration Syndrome

Prevention

• Endotracheal suctioning (Direct suction) reserved for non-vigorous infants - depressed respirations, - decreased muscle tone and/or - heart rate < 100 beats per minute

• Routine intrapartum suctioning of the oropharynx and nasopharynx of neonates delivered following labours complicated by meconium no longer recommended

1. The Neonatal Resuscitation Program of the American Academy of Pediatrics

2. Wiswell TE, Gannon CM, Jacob J, Goldsmith L, Szyld E, Weiss K. Delivery room management of the apparently vigorous meconium-stained neonate: results of the multicenter, international collaborative trial. Pediatrics. Jan 2000;105(1 Pt 1):1-7. [Medline].

Controversial

• Amnioinfusion- 1998 N Engl J Med

amnioinfusion failed to show an effect on the incidence of MAS or death.

- 2002 Cochrane Systematic Reviews

concluded that amnioinfusion was effective in decreasing the incidence of MAS

1.Hofmeyr GJ. Amnioinfusion for meconium-stained liquor in labor. Cochrane Database Syst Rev. 2002;1:CD000014.

2.Best Evidence] Fraser WD, Hofmeyr J, Lede R, et al. Amnioinfusion for the prevention of the meconium aspiration syndrome. N Engl J Med. Sep 1 2005;353(9):909-17. [Medline].

IS MECONIUM PRESENTYESNO

SUCTION MOUTH,NOSE AND POSTERIOR PHARYNX AFTER DELIVERY OF HEAD

BUT BEFORE DELIVERY OF SHOULDERS

IS THE BABY VIGOROUS?

SUCTION MOUTH AND

TRACHEA

CONTINUE WITH RESUSCITATION

CLEAR MOUTH AND NOSE FROM SECRETIONS

DRY,STIMULATE AND REPOSITION

GIVE OXYGEN AS NECESSARY

NOYES

Management

• Oxygen- hood or positive pressure

• Mechanical ventilation if necessary- oscillatory, high-frequency, jet ventilation

• Treat PPHN- Extracorporeal membrane oxygenation/inhaled nitric oxide

Meconium Aspiration Syndrome – e-Medicine.netMelinda B Clark, MD, Assistant Professor of Pediatrics, Department of Pediatrics, Albany Medical College

Surfactant Replacement Therapy

• Surfactant replacement therapy, if started within 6 hours after birth, improves oxygenation and reduces the incidence of air leaks, severity of pulmonary morbidity, and hospitalization time of term infants with MAS.

Richard D. Findlay, H. William Taeusch, and Frans J. WaltherSurfactant Replacement Therapy for Meconium Aspiration SyndromePediatrics, Jan 1996; 97: 48 - 52.

Controversial

• Antibiotics- No study to show role of infection in MAS

• Steroids- Prolongs MAS course by increasing time to wean to room air

“…antibiotic treatments would not affect the outcome of MAS…”“…meta-analysis…significant increase in hours on oxygen therapy in the steroid-treated group compared to the control group…”

Wu JM, Yeh TF, Wang JY, Wang JN, Lin YJ, Hsieh WS, Lin CH. The role of pulmonary inflammation in the development of pulmonary hypertension in newborn with meconium aspiration syndrome. Pediatric Pulmonology - Supplement 1999;18:205-208.

Prognosis

• Nearly all infants with MAS have complete recovery of pulmonary function

• Children with MAS may develop chronic lung disease as a result of intense pulmonary intervention

• Infants with MAS have a slightly increased incidence of infections in the first year of life because the lungs are still in recovery