Pediatric Cardiac Anesthesia Flashcards
Name the three branches of the aortic arch.
- Brachiocephalic (Innominate) Artery
- Left common carotid artery
- Left subclavian artery
What two arteries does the brachiocephalic artery split into?
- Right common carotid artery
- Right subclavian artery
What percentage of ventricular output will go to the lungs with a fetal heart?
5-10%
Limitation of blood flow to the lungs in a fetus is due to high __________.
PVR
How does blood flow bypass the lungs in a fetus?
- Foramen Ovale
- Ductus Arteriosus
What other organ has limited blood flow besides the lungs in a fetus?
Liver
How does blood flow bypass the liver in a fetus?
Ductus Venosus
Fetal Circulation Chart
Fetal Circulation Chart
What are three major changes in blood flow at birth?
- Marked decrease in PVR
- Increase blood flow through pulmonary veins
- Decrease placental blood flow
During birth, as blood flow to the lungs increases, what happens to Alveolar PCO2 and Alveolar PO2?
- Alveolar PCO2 Decreases
- Alveolar PO2 Increases
Usually occurs within minutes after birth
During birth, as blood flow increases through the pulmonary veins, ________ pressure becomes higher than ________ pressure.
During birth, as blood flow increases through the pulmonary veins, LEFT ATRIAL PRESSURE becomes higher than RIGHT ATRIAL PRESSURE.
During birth, as blood flow increases through the pulmonary veins, the atrial septum closes over the _____________.
Foramen Ovale
The foramen ovale is anatomically patent in _____% of children less than five years old.
50%
What happens to SVR as placental flow ceases during birth?
SVR increases
What happens to IVC flow and RA Pressure as placental flow ceases during birth?
- IVC flow decreases
- RAP decreases
What happens to the blood flow through the ductus arteriosus as placenta flow ceases during birth?
Blood flow through the ductus arteriosus reverses and fills with oxygenated blood.
What substances can be given to keep the ductus arteriosus open?
Prostaglandin
The ductus arteriosus is mostly closed by day ________ and usually completely closed by day _________.
- Mostly closed by day 2
- Completely closed by day 7
What communicates between the placenta, portal vein, and IVC?
Ductus Venosus
As the ductus venosus remains patent for several days after birth, how does this affect metabolism?
Delays Metabolism d/t reduce liver circulation
Fetal to Neonatal Circulation Chart
Fetal to Neonatal Circulation Chart
During transitional circulation, if hypoxia occurs, what will happen to PVR?
PVR increases
During transitional circulation, what will happen to the foramen ovale and ductus arteriosus if hypoxia occurs?
Foramen Ovale and Ductus Arteriosus may reopen → will cause a significant proportion of blood to bypass the lungs
List conditions that can prolong transitional circulation
- Prematurity
- Pulmonary Disease
- Hypothermia
- High Altitude
- Prolonged Stress
- Sepsis
- Acidosis
- Hypercarbia
- Congenital Heart Disease
What is unique about the RV wall of the neonatal heart?
RV wall thickness exceeds LV wall
What is the degree of axis of a neonatal heart?
180 degrees
30-90 degree axis for standard heart
Neonatal hearts have less contractile tissues, how does this affect SV and and CO?
- Limited SV d/t ↓ compliance
- CO will be rate-dependent
Why would a neonatal heart be more sensitive to CCB Drugs or Citrated Blood?
Immature myofibrils and sarcoplasmic reticulum will result in underdeveloped calcium handling mechanisms.
Due to neonatal hearts having immature myofibrils and sarcoplasmic reticulum, calcium exchange will be more dependent on the _____________-
Sarcolemma
Why does stress cause a compromised CO in a neonatal heart?
Immature Autonomic Innervation
What are the 4 types of congenital cardiac defects?
- Shunts
- Mixing Lesions
- Flow Obstructions
- Regurgitant Valves
What are the two categories of cardiac shunts?
- Intracardiac Connections (Opening between chambers)
- Extracardiac Connections (Opening between a systemic and pulmonary artery)
In Atrial Septal Defects (ASD) what is the direction and magnitude of blood flow related to?
- Ventricular Compliance
- AV Valve Function
In VSD and PDA what is the direction and magnitude of blood flow related to?
- Resistance of the Pulmonary System
- Resistance of the Systemic System
Is a Left-to-Right Shunt an Acyanotic or Cyanotic Heart Defect?
Acyanotic Heart Defect
Describe the Pulmonary Vascular Resistance in a Left-to-Right Shunt.
Low PVR
Is a Right-to-Left Shunt an Acyanotic or Cyanotic Heart Defect?
Cyanotic Heart Defect
Pulmonary Blood Flow in Left-to-Right Shunt.
Pulmonary blood flow increases d/t low PVR → Volume overload for lungs
Effects on the LV from a Left-to-Right Shunt.
- Less blood flow to the LV
- Increase workload of LV to maintain adequate CO
Examples of Left-to-Right shunt
- ASD
- VSD
- PDA
- Coarctation of the Aorta
What to avoid in a Left-to-Right Shunt.
- Vasodilators
- 100% FiO2
- ↓PCO2
- Alkalosis
Hemodynamic Consequences for Left-Right Shunt
Hemodynamic Goals for Left-Right Shunt
Pulmonary Blood Flow in Right-to-Left Shunt.
Decrease Pulmonary Blood Flow d/t PVR or Pulmonary Outflow Tract is greater than SVR → admixture of deoxygenated blood in the systemic circulation and systemic hypoxia.
What kind of ventricular failure will result from Right-to-Left Shunt?
RV Failure
Examples of Right-to-Left Shunt
- Tetralogy of Fallot
- Transposition
- Truncus Arteriosus
- Hypoplastic Left Heart
What to avoid in a Right-to-Left Shunt
- Sympathetic Stimulation
- ↓ FiO2
- ↑ PCO2
- Acidosis
Hemodynamic Consequences for Right-to-Left Shunt
Hemodynamic Goals for Right-to-Left Shunt
Effects of Volatile Anesthetics in a Right-to-Left Shunt
Inhaled Induction Prolonged (IV Induction would be preferred and much faster)
Paradoxical emboli will most likely occur in which shunt? (Right-to-Left Shunt or Left-to-Right Shunt)
Right-to-Left Shunt
What is the largest group of cyanotic lesions?
Mixing Lesions
What are Mixing Lesions?
- Congenital heart defects where oxygenated and deoxygenated blood mix together, often leading to lower levels of oxygen in the blood that circulates throughout the body.
- Pulmonary and Systemic O2 sats almost identical
Mixing Lesions are dependent on what factor?
Vascular Resistance (PVR or SVR)
Example of Mixing Lesion
Truncus Arteriosus
What are obstructive lesions?
- Condition where a heart valve, is narrowed or blocked, impeding normal blood flow.
- Conditions can range from mild to severe
Obstructive lesions can lead to pressure-overloaded ventricles proximal to the obstruction. What can this result in?
- Profound LV Failure
- Impaired Coronary Artery Perfusion
- Systemic Hypotension
- Hypoxemia
Examples of Obstructive Lesions
- Aortic Stenosis
- Coarctation of the Aorta
What causes the significant decrease in PVR after birth?
- Lung Expansion
- Oxygenation
How long does it take for a newborn’s PVR to reach the level of an adult?
6 months
Reactive PVR can lead to this condition.
Pulmonary Hypertension.
Factors that can increase PVR
Factors that can decrease PVR
What are the effects of nitric oxide on smooth vascular muscles?
Relaxes vascular smooth muscles
Can cause rebound hypertension after d/c
Neonatal Congenital Heart Surgery Preoperative Plan
- EKG
- ETT (Often nasal to prevent extubation by TEE)
- Pre/post ductal pulse ox
- Art line (usually right radial)
- Central line (usually right)
- Cerebral oximetry
- BIS
- TEE
- Pacemaker (ready)
- Blood warmer
- Level-1 infuser
Signs and Symptoms of Congenital Heart Defect
A patent foramen ovalis provides normal fetal communication between what two heart chambers?
RA and LA
When does the PFO ordinarily close?
Soon after birth
What is a Prium ASD?
ASD in the inferior part of the atrial septum, close to the AV valve.
What is a Secundum ASD?
ASD close to the fossa ovalis, defect in septum secundum.
What is Sinus Venosus?
ASD is high in the atrial septum, close to the SVC.
Coronary Sinus ASD allows blood flow from the RA to the LA through the ____________
Coronary Sinus
What is a common atrium?
- ASD with an absence of an atrial septum.
- May have some abnormal AV valves
Many ASD and VSD can be closed with a __________ device
Percutaneous Catheter
Anesthesia Considerations for ASD surgery
- Use short-acting drugs
- Often extubated on table
- Postop pulmonary hypertension rare
What is the most common congenital defect?
VSD accounts for 20% of CHD
Decribe the flow in Restrictive vs Unrestrictive VSD
- Restrictive: flow is small
- Unrestrictive: flow is large
Why may inotropic support be needed after a VSD surgery?
- To prevent pulmonary hypertension if left to right shunt was significant.
- The Right Heart may need some assistance to pump against the pulmonary pressure now the VSD is closed.
During fetal circulation, what shunt extends from the descending aorta to the main pulmonary artery?
Patent Ductus Arteriosus (PDA)
Why is PDA typical in preterm infants?
- Decrease degradation/breakdown of PGE1
- Increase production of PGE1
Where would you place preductal and postductal pulse oximetry to assess PDA?
- Preductal Pulse Ox on Right Hand
- Postductal Pulse Ox on Left Foot
If Aorta is clamped inadvertently, lower limb data may be lost
What is the most common cyanotic heart defect?
Tetralogy of Fallot
What are the four different deformities involved in Tetralogy of Fallot?
- VSD
- Overriding Aorta
- RV Outflow Obstruction (Pulmonary Stenosis)
- RV Hypertrophy
What happens during a Tet Spell?
Increased sympathetic stimulation or oxygen demand (crying, surgery, feeding, metabolic acidosis) causes increased RV outflow obstruction, causing hyper cyanosis.
What position can help increase SVR, reduce right-to-left shunting, and increase blood flow to the lungs during a Tet Spell?
- Knee-to-chest position
- Squatting
Anesthesia Considerations for TOF
- Preop Sedation
- 100% O2
- Beta Blockade
What does a complete TOF repair consist of?
Closing VSD and applying transannular patch at the level of RV Outflow Obstruction
What is a Blalock-Taussig Shunt?
- Creating a shunt from the subclavian artery to the branch of the pulmonary artery
- This will increase pulmonary blood flow in TOF patients
What two arteries are switched in the Transposition of the Great Arteries?
- Aorta coming from the RV
- Pulmonary Artery coming from the LV
- Some mixing of oxygenated and deoxygenated blood by PDA or VSD
What issue can occur without a VSD in Transposition of the Great Arteries?
- Inadequate mixing
- Repair needed early (emergent)
- LV only exposed to low pressure lung
What issue can occur with a large VSD in Transposition of the Great Arteries?
At risk of pulmonary hypertension d/t high pulm blood flow
What is the most common treatment for TGA?
- Arterial Switch
- Transection of arteries distal to valves
- Disconnection of coronary arteries and re-anastamosis to aorta
- A conduit inserted between RV and Pulmonary Artery if RV outflow is stenotic
What is truncus arteriosis?
- Congenital heart defect where a single common arterial trunk arises from the heart, instead of the usual two separate arteries (the aorta and pulmonary artery)
- Common arterial outlet
- Common valve
- VSD
High pulmonary blood flow and pulmonary hypertension develops early
What syndrome is associated with Truncus Arteriosis?
DiGeorge Syndrome
Characteristics of DiGeorge Syndrome
- Aortic arch abnormalities
- Absent Parathyroids
- Immune Deficiency
Anesthesia Considerations for Truncus Arteriosis
- Already intubated and on inotropes
- Irradiated blood
- Close watch of calcium levels
- Circulation arrest may be required
- Nitric oxide postop
Characteristics of Hypoplastic Left Heart Syndrome (HLHS)
- Hypoplastic LV
- Mitral stenosis/ atresia (closed)
- Aortic stenosis/ atresia
- Hypoplastic Aortic Arch
- ASD
How many surgeries does it take to repair Hypoplastic Left Heart Syndrome?
3 stages (Norwood, Glenn, Fontan procedure)
Typical O2 saturation of children with Hypoplastic Left Heart Syndrome
80’s
Anesthesia Considerations for HLHS
- Balance PVR and SVR
- High PVR → Cyanosis
- Low PVR → Pulmonary overload, systemic hypoperfusion (acidosis)
- Keep PaCO2 high/Normal → Keep Vasodilation
- Keep FiO2 low → Prevent Vasoconstriction
