Meconium Aspiration syndrome.pptx

MEUCONIUM ASPIRATION SYNDROME

1. Meconium Aspiration syndrome Moderator Assoc. Prof. Dr. Sunil Kumar Yadav Department of Pediatrics and Adolescent Medicine Nobel Medical College & Teaching Hospital Presenter: Dr Subodh Kumar Shah 2 nd year Resident Pediatric

2. Defination : Meconium is a sterile, thick, black-green, odorless material that results from the accumulation of debris in the fetal intestine starting in the third month of gestation . (Cloherty-and-Starks-Manual-of-Neonatal-Care-2021) Meconium is sterile and does not contain bacteria, which is the primary factor that differentiates it from stool. Intrauterine distress can cause passage of meconium into the amniotic fluid .

3.  In the fetus, passage of meconium first occurs physiologically in the 10th-16th week of gestation, when it contributes to alkaline phosphatase in amniotic fluid. • Fetal defecation reduces after 16 weeks and stops by 20 weeks, concurrent with innervation of the anal sphincter. • In-utero meconium passage is uncommon till term due to: o lack of strong peristalsis o good anal sphincter tone o low levels of motilin o cap of viscous meconium in the rectum • Because meconium is rarely found in the amniotic fluid before 34 weeks gestation , MAS mainly affects infants at term and post-term beyond 42 weeks .

4. Incidence: Meconium-stained amniotic fluid (MSAF ) complicates approximately 10% to 15% of deliveries. The incidence of MSAF in preterm infants is very low. Most babies with MSAF are 37 weeks or older, and many meconium-stained infants are post mature and small for gestational age. Approximately 3% to 4% of neonates born through MSAF develop meconium aspiration syndrome (MAS), and Approximately 30% to 50% of these infants require continuous positive airway pressure (CPAP) or mechanical ventilation.

5. Meconium Aspiration Syndrome: “Respiratory distress in newborn infants from inhalation of meconium stained amniotic fluid into the tracheobronchial tree with compatible radiological findings which cannot be otherwise explained.”

6. Causes:

7. Etiology: IN MOTHER IN FETUS  -Maternal hypertension/ DM -Heavy cigarette smoking -Chronic Respiratory or CVS disease -Post-term pregnancy -Pre- eclampsia / eclampsia - Oligohydramnios -Intrauterine growth retardation -Poor biophysical profile -Abnormal fetal heart rate patterns

8. 1.Mechanical obstruction Thick and viscous meconium lead to Complete or partial airway obstruction. With onset of respiration – meconium migrates from central to peripheral airways. Complete obstruction – atelectasis Partial obstruction –Ball-valve – air trapping. Risk of pneumothorax - 15 – 33% PATHOPHYSIOLOGY

9. Aspiration of meconium causes airway irritation. The enzymes and bile salts of meconium may cause a release of cytokines ( eg , tumor necrosis factor-1-alpha and interleukins-1B , -6, -8, -13), which can result in diffuse toxic pneumonitis . With distal progressing of meconium, chemical pneumonitis develop resulting bronchiolar edema and narrowing of the small airway. 2. Chemical pneumonitis:

10. 3. Surfactant inactivation: Meconium has cytotoxic effect on type II pneumocytes and decreased levels of surfactant protein A and B (SP-A and SP-B). Bilirubin , fatty acid, triglycerides, cholesterol content of meconium causes alterations in phospholipid structure . Bile salts in meconium may inhibit surfactant synthesis.

11. Contd … Several constituents of meconium, especially the free fatty acids ( eg , palmitic , stearic, and oleic acid), have a higher minimal surface tension than surfactant. These may displace it from the alveolar surface , resulting in diffuse atelectasis, with decreased lung volume, compliance, and oxygenation . The effect of MAS on surfactant dysfunction usually occurs in the subacute and late phase of the disease.

12. 4. Persistent pulmonary hypertension ( PPHN) Persistent pulmonary hypertension of the newborn (PPHN) frequently accompanies MAS, with right-to-left shunting caused by increased pulmonary vascular resistance . PPHN usually presents in the subacute phase and as persistent hypoxemia at 6 to 24 hours after birth. Significant pulmonary hypertension with right-to-left shunting occurs in about 20% to 40% of infants who have MAS .

13. PPHN in infants who have MAS could be due to: 1) hypertrophy or neomuscularization of post- acinar capillaries as a result of chronic intrauterine hypoxia . 2) pulmonary vasoconstriction as a result of hypoxia, hypercarbia , or acidosis . 3) pulmonary vasoconstriction as a result of lung inflammation

14. ( Wiswell )

15.  Physical Examination Symptoms include the following: o Cyanosis o End-expiratory grunting o Alar nasal flaring o Intercostal retractions o Tachypnea o Barrel chest (increased anteroposterior diameter) due to the presence of air trapping o Auscultated rales and rhonchi (in some cases ) Yellow-green staining of fingernails, umbilical cord, skin or under the vocal cords. Signs of cerebral irritation resulting from cerebral edema and hypoxia may appear later after birth i.e. seizures or jitteriness

16. Thank you……..

17. Reference: Wiswell , T.E.; Tuggle , J.M.; Turner, B.S. Meconium aspiration syndrome: Have we made a difference? Pediatrics 1990 , 85 ,715–721.[ PubMed ] Clearly , G.M.; Wiswell , T.E. Meconium-stained amniotic fluid and the meconium aspiration syndrome: An update. Pediatr.Clin.N . Am. 1998 , 45 , 511–529. [ CrossRef ] Manual of Neonatal Care 8th edition John P. Cloherty Essential Pediatrics 8th edition, O.P Ghai Neonatal Resuscitation Manual • Clarke, M.B. and Rosenkrantz , T. (2016) Meconium aspiration syndrome: Background , Pathophysiology, prognosis. Available at:http ://emedicine.medscape.com/article/974110-overview#a5 (Accessed: 5 July 2016 )