Definition Risk Factors - Prematurity
- Male
- Hypothermia
- Maternal diabetes
- Cesarian
- Perinatal asphyxia
- Multiple pregnancy
- FHx of RDS
Differential diagnosis Epidemiology - Affects about 1% of newborn infants and is the leading cause of death in preterm infants
- Incidence decreases with advancing gestational age
- About 50% in babies born at 26–28 weeks
- About 25% at 30–31
weeks
- > 90% at 28 weeks?
- 50% at 32 weeks?
- More frequent in infants of diabetic mothers and
in the second born of premature twins
Aetiology - Surfactant deficiency
- => full lung closure on expiration
Clinical features - tachypnea
- tachycardia
- chest wall retractions (recession)
- expiratory grunting
- breath against a partially closed glottis
- flaring of the nostrils
- cyanosis
- Progression over 2-3 days
- More O2 required
- Either => death or recovery by 72 h
Pathophysiology - Deficit in surfactant
- Complex system of lipids, proteins and glycoproteins
- Produced in specialized lung cells called Type II cells or
Type II pneumocytes
- Packaged by the cell in
structures called lamellar bodies,
and extruded into the air-spaces
- Unfold into
a complex lining of the air-space
- 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
- Prevents the air-spaces from completely collapsing on exhalation
- Allows re-opening of the
air-space with a lower amount of force
- Without adequate
amounts of surfactant, the air-spaces collapse and are very difficult
to expand
- Lungs are characterized by collapsed air-spaces alternating with hyper-expanded
areas, vascular congestion and, in time, hyaline membranes.
- As a result, blood passing
through the lungs is unable to pick up oxygen and unload carbon
dioxide
- Structural immaturity, as manifest by decreased number of gas-exchange
units and thicker walls, also contributes to the disease process
- Therapeutic oxygen and positive-pressure ventilation, while potentially
life-saving, can also damage the lung
Investigations- Fetal lung maturity may be tested by sampling the amount of surfactant
in the amniotic fluid, obtained by inserting a needle through the
mother's abdomen and uterus
- Several tests are available that correlate
with the production of surfactant
- Blood gases
- respiratory and metabolic acidosis along with hypoxia
- CXR
- Pulmonary mechanics testing (PMT)
Management
http://eng.mapofmedicine.com/evidence/map/respiratory_distress_syndrome1.html a) conservativeb) medical - Pre-term glucocorticoids speed the production of surfactant
- Ventilation
- High frequency oscillatory ventilation
- Continuous positive airway pressure (CPAP)
- High-speed mechanical ventilation (> 40 breaths per min)
- Oxygen
- Intravenous fluids to stabilize the blood sugar, blood salts, and blood pressure
- Extracorporeal membrane oxygenation (ECMO)
- Not appropriate for premature babies
- Exogenous surfactant
- Pig better than synthetic
c) surgicalPrognosis- Most common single cause of death in the first month of life of the
developed world
- Complications:
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