INFANT RESPIRATORY DISTRESS SYNDROME

MIHAI CRAIU MD PhD

TERMINOLOGY

• Hyaline membrane disease; • Infant respiratory distress syndrome

(IRDS); • Respiratory distress syndrome in

infants;• RDS - infants

IRDS

• Syndrome caused in premature infants by developmental insufficiency of surfactant production and structural immaturity in the lungs.

IRDS

• It can also result from a genetic problem with the production of surfactant associated proteins.

• RDS affects about 1% of newborn infants and is the leading cause of death in preterm infants.

CRONOLOGY

• The earlier a baby is born, the less developed the lungs are and the higher the chance of IRDS.

• Most cases are seen in babies born before 28 weeks.

• It is very uncommon in infants born full-term (at 40 weeks).

INCIDENCE 1

• Frequency increases as gestational age decreases:– GA < 30 weeks ~ 60%– GA 30 – 34 weeks ~ 25%– GA > 34 weeks ~ 5%– Term newborn << 1%

INCIDENCE 2

• Frequency decreases with ante-partum steroid treatment :– GA < 30 weeks ~ 35%– GA 30 – 34 weeks ~ 10%– GA > 34 weeks ~ 1%– Term newborn – virtually no cases

SURFACTANT 1

• The lungs of infants with respiratory distress syndrome are developmentally deficient in surfactant.

• Surfactant is a complex system of lipids, proteins and glyco-proteins which are produced in specialized lung cells called Type II cells or Type II pneumocytes.

SURFACTANT 2

• The surfactant is packaged by the cell in structures called lamellar bodies, and extruded into the air-spaces.

• The lamellar bodies then unfold into a complex lining of the air-space.

SURFACTANT 3

• Surfactant helps prevent collapse of the terminal air-spaces throughout the normal cycle of inhalation and exhalation.

• This layer reduces the surface tension of the fluid that lines the air-space.

• Surface tension is responsible for approximately 2/3 of the elastic recoil forces.

HYALINE MEMBRANE

HYALINE MEMBRANE

RISK FACTORS FOR IRDS

• Prematurity (most frequent) • A brother or sister who had RDS• Diabetes in the mother• Cesarean delivery• Delivery complications that lead to

acidosis in the newborn at birth• Multiple pregnancy (twins or more)• Rapid labor

PROTECTIVE FACTORS FOR IRDS

• Maternal prenatal stress– High BP– Toxemia

• Maternal infection before birth• Intrauterine failure to thrive• Steroid treatment before labor

CLINICAL COURSE 1

Newborn has one or more of the physical signs of respiratory distress

• Tachypnoea tahipnee • Chest retractions retractii costale• Cyanosis cianoza• Grunting geme• Flaring of ala nasi(bate dn nari)• Thoraco-abdominal balance(balans

toraco abd)• Bobbing of the head( da dn cap)

Tachypnoea & Chest retractions

Bobbing of the head

Flaring of ala nasi (nostrils)

CLINICAL COURSE 2

• As the disease progresses, the baby may develop – ventilatory failure (rising carbon dioxide

concentrations in the blood), – prolonged cessations of breathing

("apnea")

• Whether treated or not, the clinical course for the acute disease lasts about 2 to 3 days.

CLINICAL COURSE 3

• During the first, the patient worsens and requires more support.

• During the second the baby may be remarkably stable on adequate support

• Usually resolution is noted during the third-fourth day, heralded by a prompt diuresis.

• By day 7 complete resolution.

PREVENTION 1

• Most cases of hyaline membrane disease can be ameliorated or prevented if mothers who are about to deliver prematurely can be given glucocorticoids.

• This speeds the production of surfactant.

• For very premature deliveries, a glucocorticoid is given without testing the fetal lung maturity.

PREVENTION 3

• The lecithin-sphingomyelin ratio ("L/S ratio"),• if the result is less than 2:1, the fetal lungs may be

surfactant deficient.

– The presence of phosphatidol-glycerol (PG),• The presence of PG usually indicates fetal lung maturity.

– The surfactant/albumin (S/A) ratio. • The result is given as mg of surfactant per gm of protein. • An S/A ratio <35 indicates immature lungs, • Between 35-55 is indeterminate, • >55 indicates mature surfactant production (correlates

with an L/S ratio of 2.2 or greater).

RADIOLOGY 1

• Typically, diffuse “ground-glass” opacification of both lungs with air bronchograms and hypoaeration

• Fine granular pattern• Prominent air

bronchograms• Bilateral and symmetrical

distribution

PREVENTION 2

• In pregnancies of greater than 30 weeks, the fetal lung maturity may be tested by sampling the amount of surfactant in the amniotic fluid, obtained by amniocenthesis.

• Several tests are available that correlate with the production of surfactant. – The lecithin-sphingomyelin ratio ("L/S ratio"),– The presence of phosphatidol-glycerol (PG),– The surfactant/albumin (S/A) ratio.

RADIOLOGY 2

• Hypoaeration from loss of lung volume (may be counteracted by respiratory therapy)

DIFFERENTIALS

• RDS• Transient Tachypnea• Meconium aspiration• Other aspiration sy (milk,

amniotic fluid)• Pneumothorax• Pneumonia• Pulmonary hemorrhage• Atelectasis • Lung anomalies (cysts,

sequestration, adenomat m)

• Diaphragmatic hernia• Choanal atresia• Congenit heart defects• Cardiac failure• Myocarditis• Persistent foetal circulation• Polycythemia• Anemia• Septicaemia / meningitis• Drugs to mother in labour

TREATMENT 1

• Oxygen is given with a small amount of continuous positive airway pressure ("CPAP").

• Intravenous fluids are administered to stabilize the blood sugar, blood salts, and blood pressure.

TREATMENT 2

• If the baby's condition worsens, an endotracheal tube (ET tube) is inserted into the trachea and intermittent breaths are given by a mechanical device (conventional of HF ventilator).

• In extreme cases ECMO

TREATMENT 3

• Such small premature infants may remain ventilated for months.

TREATMENT 4

• An exogenous preparation of surfactant, either synthetic or extracted from animal lungs, can be given through the ET tube into the lungs.

TREATMENT 5

• Commonly used surfactants are– SURVANTA derived from bovine lung– CUROSURF derived from porcine lung– EXOSURF – artificial, from human lung

• Dose:– 100 mg/kg for natural surfactant– 25-100 mg/kg for artificial surfactant

COMPLICATIONS 1

• The mortality rate for babies greater than 27 weeks gestation is less than 10% in USA.

• The disease is frequently complicated by prematurity-related co-morbid diseases.

COMPLICATIONS 2

• Complications include:– metabolic disorders

(acidosis, low blood sugar),

– patent ductus arteriosus, – low blood pressure,– pulmonary hypertension – chronic lung changes, – intracranial hemorrhage,– alveolar hemorrhage

MECHANICAL COMPLICATIONS

Surfactant decreases

PTX rate with 60% and death rate by 30-40%

PNEUMOTHORAX

CHRONIC COMPLICATIONS 1

• Lobar emphysema

• Localized interstitial emphysema

• Recurrent respiratory tract infections

CHRONIC COMPLICATIONS 2

• Rethinopathy of prematurity (Retrolental fibroplasia )- ROP

• Subglottic stenosis from intubation

• Failure to thrive

CONCLUSSION

• IRDS is caused in premature infants by insufficiency of surfactant production.

• Prenatal treatment with steroids!!• Postnatal treatment with surfactant!!!• Ventilatory support is crucial!!• First week is crucial for survival!!• Sequelae : ROP, BDP, hiperreactive

airway