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 are treatment methods/goals for RDS?
- Surfactant administration via ETT (endotracheal tube)
- There is a limit; too many doses can cause particulates of surfactant and “junky lung”
- Maintain optimal tidal volume in the face of changing compliance to ensure lung is not damaged
- Prevent alveoli from collapsing; use PEEP (peak end expiratory pressure)
- Re-dose surfactant as needed (up to 3 times)
- Extubate as soon as possible (ventilator may damage lungs)
Describe the physiology of air leaks
- Occurs when there is over distention, air trapping, or uneven distribution of gas
- Rupture of an over-distended alveolus
- Air dissects along the perivascular connective tissue sheath
Where are air leaks located anatomically?
- Pneumothorax: presence of air or gas in the pleural cavity (ie, the potential space between the viscera and parietal pleura of the lung)
- Pneumomediastinum: gas in the mediastinal tissues that can occur when air leaks through small alveolar ruptures to the surrounding bronchovascular sheath
- Pulmonary interstitial emphysema (PIE): air trapped and tracking along perivascular/peribronchial tissues of the lung (doesn’t go anywhere; doesn’t collect in pleural cavity or mediastinum; remains peribronchial)
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)
What is the therapeutic approach to air leaks?
It depends on the type of air leak
- No intervention if not causing clinical deterioration
- Thoracosentesis/”needle” evacuation of air for penumothorax or pneumomediastinum
- Chest tube for persistent pneumothorax
- High Frequency Oscillatory Ventilation (HFOV) for PIE
- Tiny TVs at very high rate (Can’t use needle to evacuate PIE air)
How may cyanotic heart disease present?
- Cyanosis and/or tachypnea
- Heart failure (low liver)
- Heart disease can coexist with pulmonary disease
What are “the 5Ts” of cyanotic heart disease?
- Tetralogy of Fallot
- Transposition of the great arteries
- Truncus arteriosus
- Total anomalous pulmonary venous return: TAPVR
- Tricuspid valve abnormalities (Atresia and Ebstein’s)
How do you differentiate cardiac from lung disease? (Important slide)
- History and prenatal ultrasound
- Possible physical findings:
- Cyanosis, Gallop rhythm, Mild respiratory distress, enlarged liver (if in failure)
- “Hyper-oxygenation Test”
- Increase inspired oxygen to 100% for 10-15 minutes
- PaO2 usually 150 mm Hg if lung disease
- ECHO is diagnostic
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 in CXR of Tetrology of Fallot?
- CXR with “boot shaped” heart
- Upturned apex
- Normal heart size; normal or decreased pulmonary vascular markings
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 on CXR of Transposition of the Great Arteries?
- CXR with “egg on a string”
- Increased pulmonary vasculature
- Narrow mediastinum as the great arteries are running parallel
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 on CXR of Truncus Arteriosus?
- Cardiomegaly
- Pulmonary congestion(mainly as result of collateral formation)
- Widened mediastinum
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 on CXR of Total Anomalous Pulmonary Venous Return (TAPVR)?
- CXR with “snowman shape”
- The pulmonary veins drain into an enlarged vertical vein
- Bridging vein drains superior vena cava (red arrow)
- Results in significant pulmonary edema
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 seen on CXR with tricuspid atresia?
No significant radiographic findings
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 on CXR of Tricuspid Valve Anomaly: Ebstein’s anomaly?
- Associations
- Increased risk of what
- Thought be associated with maternal lithium use
- Increased risk of WPW syndrome secondary to accessory pathways
- Can include lung hypoplasia in cases of extremely large right atrium that restricts pulmonary development
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
