Neonatal hypoxia-Marks Flashcards
What is the most common reasons neonates are ventilated?
Respiratory distress syndrome (aka Hyaline Membrane Disease)
What is the incidence of RDS in a term baby?
5%
At what age is gas exchange possible (but no surfactant)?
20 weeks.
When does surfactant begin to form?
31 weeks
What is the composition of surfactant?
80% phospholipids (mostly phsophatidylcholines/lecithin), 12% proteins important for distribution across surface.
When is surfactant most critical?
During exhalation when alveoli collapse
What appears on a CXR with lack of surfactant?
White lungs from alveolar collapse
What is the role of surfactant proteins SPA and SPD?
Compact proteins into lamellar bodies, distribute onto surface and help recycle it. Defend against infeection by stimulating phagocytosis and activating alveolar macrophages.
What is the consequence of lacking surfactant B?
Enough surfactant but severe respiratory distress, essential for film formation, die shortly after birth.
What is the consequence of SPC deeficiency?
Some respiratory distress, problems in film formation, but more likely to survive than SPB deficiency.
What does the ABCA3 transporter do?
Exports surfactant through lamellar bodies after production in the ER/Golgi with proteins.
Pressure/Volume Curve with hyaline membrane disease/RDS
HMD/RDS collapses alveoli and decreases lung compliance which collapses, no residual volume and collapse of curve, worsens with atelectasis over time.
What is the effect of lavaged lung?
More pressure to reach same volume. If lavaged and treated with surfactant, better. Highest slope is unlavaged.
What is the Laplace equation for surface tension?
Pressure required to prevent collapse of airspace (P)=2xsurface tension/radius. Less pressure needed with increased radius.
How is lecithin in amniotic fluid used to detect surfactant?
Theoretically can measure amounts but in reality if baby is premature give drug for surfactant (steroids).
How is the lecithin/sphingomyelin ratio used?
Higher with higher gestational age, if over 2, negligible chance of RDS. If
What should be suspected with a mature baby with RDS?
Protein or transporter defect, especially if high response to exogenous surfactant.
Pathophysiology of RDS
Reduced ventilation, reduced lung compliance, reduced lung volume, increased work to breathe, increased pCO2–>vasoconstriction. Hypoxia, hypertachypneia, dyspnea, other preterm problems, V/Q mismatch (oxygen but not perfusion), acidosis (resp and metabolic)
Factors that increase risk of RDS
Prematurity, maternal diabetes, perinatal asphyxia, C-section without labor.
What factors decrease risk of RDS?
Pregnancy induced hypertension, stress before birth, small for gestational age, smoking, all things that make the b aby chronically hypoxic, not good for growth or development and delivery difficult but less RDS risk.
What is the consequence of keeping the alveoli open during the first 72 hours by high pressure ventilation?
Pneumothorax (but got better)
What is the differential diagnosis with RDS?
Pneumonia. Both seen similarly in bronchogram.
Labs for RDS
Blood gases: hypoxia, hypercarbia, mixed acidosis. Dehydration, hypernatremia. Infection is a cause for preterm labor, leukopenia and thrombocytopenia with concurrent infection.
How to treat RDS
Prevent hypoxia and hyperoxia (free radical injury), prevent atelectasis and collapse of alveoli and accumulation of fluid and make sure not traumatizing lungs by ventilation at early stage of lung development. Continuing trying to keep baby alive, minimize higher O2 to wean and minimize lung damage. Supportive management for preterm. CPAP, surfactant instillation (animal so proteins).
What is CPAP (continuous pulmonary airway pressure)?
Flow of pressure the whole time (at end of expiration pressure is still there so won’t let alveoli collapse even with deficiency). Babies usually create own CPAP. Preterm babies close vocal chords to close airways to maintain air during exhalation. May make them come out quicker.
Indications of mechanical ventilation
By need, not by age: pCO2>60 with pH
Long term complications of RDS
Developmental problems (cognitive and neuromotor and behavioral), intracranial hemorrhage/interventricular hemorrhage in babies that are not stable from rapid fluctuations (treated with steroids). By reducing amount of respiratory distress also improve neurodevelpmental outcome (in addition to ventilation). Also PDA, bronchopulmonary dysplasia, retinopathy of prematurity, neurological impairment (of low birth weight infants).
Bronchopulmonary dysplasia
Used to be in bigger babies. Old BPD: fibrosis and damage of alveoli. New BPD: damage through ventilation and perfusion. Worse than fibrosis, also pulmonary hypertension. Defined as continuing requirement of ventilation even after gestational maturity has been reached.
What is cerclage?
Narrowing of the cervix surgically to prevent premature birth after late abortions or previous premature births.
Use of antenatal steroids
The earlier the better (1-7 days most effective and with earlier gestational age-
