Neonatal hypoxia-Marks

Question 1

What is the most common reasons neonates are ventilated?

Answer 1

Respiratory distress syndrome (aka Hyaline Membrane Disease)

Question 2

What is the incidence of RDS in a term baby?

Answer 2

5%

Question 3

At what age is gas exchange possible (but no surfactant)?

Answer 3

20 weeks.

Question 4

When does surfactant begin to form?

Answer 4

31 weeks

Question 5

What is the composition of surfactant?

Answer 5

80% phospholipids (mostly phsophatidylcholines/lecithin), 12% proteins important for distribution across surface.

Question 6

When is surfactant most critical?

Answer 6

During exhalation when alveoli collapse

Question 7

What appears on a CXR with lack of surfactant?

Answer 7

White lungs from alveolar collapse

Question 8

What is the role of surfactant proteins SPA and SPD?

Answer 8

Compact proteins into lamellar bodies, distribute onto surface and help recycle it. Defend against infeection by stimulating phagocytosis and activating alveolar macrophages.

Question 9

What is the consequence of lacking surfactant B?

Answer 9

Enough surfactant but severe respiratory distress, essential for film formation, die shortly after birth.

Question 10

What is the consequence of SPC deeficiency?

Answer 10

Some respiratory distress, problems in film formation, but more likely to survive than SPB deficiency.

Question 11

What does the ABCA3 transporter do?

Answer 11

Exports surfactant through lamellar bodies after production in the ER/Golgi with proteins.

Question 12

Pressure/Volume Curve with hyaline membrane disease/RDS

Answer 12

HMD/RDS collapses alveoli and decreases lung compliance which collapses, no residual volume and collapse of curve, worsens with atelectasis over time.

Question 13

What is the effect of lavaged lung?

Answer 13

More pressure to reach same volume. If lavaged and treated with surfactant, better. Highest slope is unlavaged.

Question 14

What is the Laplace equation for surface tension?

Answer 14

Pressure required to prevent collapse of airspace (P)=2xsurface tension/radius. Less pressure needed with increased radius.

Question 15

How is lecithin in amniotic fluid used to detect surfactant?

Answer 15

Theoretically can measure amounts but in reality if baby is premature give drug for surfactant (steroids).

Question 16

How is the lecithin/sphingomyelin ratio used?

Answer 16

Higher with higher gestational age, if over 2, negligible chance of RDS. If

Question 17

What should be suspected with a mature baby with RDS?

Answer 17

Protein or transporter defect, especially if high response to exogenous surfactant.

Question 18

Pathophysiology of RDS

Answer 18

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)

Question 19

Factors that increase risk of RDS

Answer 19

Prematurity, maternal diabetes, perinatal asphyxia, C-section without labor.

Question 20

What factors decrease risk of RDS?

Answer 20

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.

Question 21

What is the consequence of keeping the alveoli open during the first 72 hours by high pressure ventilation?

Answer 21

Pneumothorax (but got better)

Question 22

What is the differential diagnosis with RDS?

Answer 22

Pneumonia. Both seen similarly in bronchogram.

Question 23

Labs for RDS

Answer 23

Blood gases: hypoxia, hypercarbia, mixed acidosis. Dehydration, hypernatremia. Infection is a cause for preterm labor, leukopenia and thrombocytopenia with concurrent infection.

Question 24

How to treat RDS

Answer 24

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).

Question 25

What is CPAP (continuous pulmonary airway pressure)?

Answer 25

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.

Question 26

Indications of mechanical ventilation

Answer 26

By need, not by age: pCO2>60 with pH

Question 27

Long term complications of RDS

Answer 27

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).

Question 28

Bronchopulmonary dysplasia

Answer 28

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.

Question 29

What is cerclage?

Answer 29

Narrowing of the cervix surgically to prevent premature birth after late abortions or previous premature births.

Question 30

Use of antenatal steroids

Answer 30

The earlier the better (1-7 days most effective and with earlier gestational age-