11/13- Intro to Clinical Pedi Cardio-Pulmonary Interactions Flashcards
Describe transitional circulation in utero
- Oxygenated blood from placenta -> umbilical veins
- Portal sinus into liver
- Ductus venosus shunts around liver (still highly oxygenated)
- Rejoin into IVC -> heart
- Shunted from R atrium into L atrium (foramen ovale)
- Blood that does go to R ventricle/pulmonary a is shutned into aorta through ductus arteriosus
- Systemic circulation out to organs
- Veins collect and form umbilical arteries going back to placenta
Describe transitional circulation/changes after birth
- Foramen ovale closes
- Ductus arteriosus closes
- Ductus venosus closes (?)
What is Persistent Pulmonary Hypertension of the Newborn (PPHN)?
- Consequences
Failure of normal circulatory transition after delivery
- Elevated pulmonary pressures result in right-to-left shunting via extra-pulmonary pathways
- Patent Foramen Ovale (PFO)
- Patent Ductus Arterious (PDA)
What are the most critical signals for successful transition (not PPHN)?
- Distension of the lung (crying/breathing)
- Increase in oxygen tension in the lungs
- Decrease in CO2 tension
How do you recognize PPHN?
- Birth history (how long before crying, activity)
- Low PaO2
- Low sats with discordant pre/post ductal sats
- If ductus arteriosus connects between some of the early aortic branches (i.e. after brachiocephalic going R but before L common carotid and L subclavian), will see oxygen saturation R > L
- Echocardiogram
What is seen here?
Persistent Pulmonary Hypertension of the Newborn (PPHN)
- Only see air (abnormally dark lung fields); no vessel markings
Describe treatment approach to PPHN
- Keep baby well oxygenated (PaO2 values are important)
- Keep pH in normal range (acidosis worsens PPHN)
- Pulmonary vasculature is very sensitive to pH
- Consider increasing systemic blood pressures (dopamine)
- Try to shunt blood into pulmonary system
- Keep baby’s environment quiet/calm, consider sedation
- Consider iNO (inhaled nitric oxide)
- Oxygen is the most potent vasodilator in the lung, but NO is second
What are common newborn lung diseases?
- Transient tachypnea of the newborn (TTN)
- Respiratory distress syndrome (RDS)
- Air leaks
What causes Transient Tachypnea of the Newborn (TTN)?
- Most common cause of what
- Risk factors for TTN
Caused by retained fetal lung fluid (RFLF)
- The fetal lung is a secretory organ in utero (secretions produce pressure that allow lungs to grow)
- Sidenote: babies with renal hypoplasia who are not peeing/contributing to amniotic fluid have decreased external P and are losing lung secretions contributing to pulmonary hypoplasia
Most common cause of respiratory distress in newborns
Risk Factors for TTN
- Premature delivery
- Elective c-section delivery (no labor)
- Labor signals fetus to stop secreting fluid
- Precipitous delivery
- Delayed clamping of umbilical cord
- Maternal diabetes
- Maternal sedation
What are TTN findings on CXR?
- Normal inflation
- “Streaky” or “sunburst” pattern of linear densities emanating from the hilum (fluid in the fissure)
- Occasionally, fluffy densities from alveolar flooding are present
What is seen here?
Transient Tachypnea of the Newborn (TTN)
- Sharp line in middleish of right lung on left picture is fluid in fissure (big sign of TTN)
- White puffy area of fluid of right lung on right picture are just puddles of lung fluid
How is TTN diagnosed?
- Diagnosis of exclusion
- Be sure to rule out pulmonary HTN
- Self-resolving disease (will reabsorb lung fluid)
- Oxygen need highest initially, then decreases progressively (does not present days after delivery)
- Oxygen need rarely exceeds 40%
- Positive pressure usually not required (TTN is present at birth/presents within an hour or so; not something that shows up later! Think something else)
What is Respiratory Distress Syndrome (RDS)?
- Aka
- Caused by
- Incidence
- Also called Hyaline Membrane Disease (HMD)
- Due to Surfactant deficiency
- Incidence: ~40,000 infants/year
- 60-80% of infants born < 28 weeks (pre-steroid estimates; with steroids, you have increased fetal ability to produce surfactant)
What is surfactant?
- Composition
- Synthesis begins when
- Produced by what cells
- What affects maturation of cell line
- 75% phospholipid, 10% protein
- Synthesis begins at 24-28 weeks gestation
- Why “edge of viability” is around 23 wks
- Produced by Type II Pneumocytes
- Maturation of cell line is:
- Delayed by fetal hyperinsulinemia and
- Enhanced by chronic stress (e.g. babies of drug using mothers may actually have more mature lungs)
How does surfactant work?
- Without surfactant, there is progressive cellular damage from ventilation of collapsed alveoli
- Damage causes eosinophilic exudative proteinaceous material (HMD)
- Fibrosis occurs and lung scars down, leading to poor oxygen transport
- Surfactant maintains alveolar expansion by decreasing surface tension
- Increases compliance
- Improves oxygen transport through membrane
What are RDS findings on CXR?
- Low lung volumes (since no surfactant to allow good compliance)
- Visible air bronchograms
- Lung “texture”
- Fine
- Homogeneous (unlike TTN)
- Granular
- Ground-glass
What is seen here?
Respiratory Distress Syndrome (RDS)
- Fine, homogeneous granular appearance
What is seen here?
Air leak: pneumothorax
What is seen here?
Air leak: pneumomediastinum
- On left: thymus being raised due to air arround the heart
What is seen here?
Air leak: Pulmonary interstitial emphysema (PIE)
Describe Tetrology of Fallot
- Partial obstruction (stenosis) of right ventricular outflow (to lungs) and pulmonary valve
- Increased outflow in aorta
- Thickened (hypertrophic) R ventricle hypertrophy
What is seen here?
Tetrology of Fallot
- CXR with “boot shaped” heart
- Upturned apex
- Normal heart size; normal or decreased pulmonary vascular markings
Describe Transposition of the Great arteries
- Where are things connected
- Treatment
Structure
- Aorta arises from right ventricle
- Pulmonary artery arises from left ventricle
- This creates circulation in parallel
- Survival requires mixing of the two circulations (PDA)
Often a bedside septostomy if PDA closes
What is seen here?
Transposition of the Great Arteries
- CXR with “egg on a string”
- Increased pulmonary vasculature
- Narrow mediastinum as the great arteries are running parallel
Describe Truncus Arteriosus
- Structure
- Consequences
- Lack of separation of the embryological truncus into a separate aorta and pulmonary trunk
- Results in single arterial vessel leaving the heart
- May also result in a common truncal valve which can contain 2 - 4 cusps
What is seen here?
Truncus Arteriosus
- Cardiomegaly
- Pulmonary congestion(mainly as result of collateral formation)
- Widened mediastinum
What is Total Anomalous Pulmonary Venous Return (TAPVR)?
- Structure
- No connection between pulmonary veins and left atrium
- Bridging veins converge in a common confluence just posterior to the atrium
- Confluence drains into a systemic vein/veins
- Blood reaches the LV via an ASD
What is seen here?
Total Anomalous Pulmonary Venous Return (TAPVR)
What is Tricuspid atresia?
- Structure
- Associations
- Associated with VSD and ASD (PFO), small RV and main PA
- Blue blood goes to LV gets to the lung via VSD and PDA
What is Ebstein’s Anomaly?
Tricuspid Valve Anomaly
- Downward displacement of the tricuspid leaflets into the right ventricle
- Right ventricle communicates with the right atrium resulting in enlarged right atrium with hypoplastic right ventricle
- Usually has an intracardiac shunt (ASD)
What is seen here?
Tricuspid Valve Anomaly: Ebstein’s anomaly
- Can include lung hypoplasia in cases of extremely large right atrium that restricts pulmonary development
