Cardiac shunts Flashcards
What is the ductus venosus? When does it close?
Allows blood to bypass the liver
Umbilical vein to the IVC
Clamping of the cord
What is the foramen ovale? When does it close?
Allows blood passage from RA to LA to bypass the lungs
3 days
What is the ductus arteriosus? When does it close?
Shunts blood away from pulmonary trunk
Pulmonary artery to the proximal descending aorta
Weeks after birth
How does PVR and SVR compare in fetal circulation to adults?
PVR is high in fetus
SVR is low in fetus
Which organ is responsible for respiration in the fetus? How is circulation arranged?
Placenta for respiration
Circulation is arranged in parallel
What type of shunting occurs in the fetus?
R - L across foramen ovale and the ductus arteriosus
Is there pulmonary blood flow in the fetus? Is left atrial pressure high or low?
Minimal pulmonary blood flow
LA pressure is low
What happens to PaO2, PaCO2, and PVR when baby takes first breath of life?
PaO2 Increases
PaCO2 Decreases
PVR Decreases
What happens to the placenta and SVR when baby takes first breath of life?
Placenta detaches and SVR increases
How does the foramen ovale close when baby takes first breath of life?
Decreased PVR and Increased SVR cause higher pressure in the LA than the RA and the flap closes
How does the ductus arteriosus close?
Decreased PVR reverses blood which exposes the Ductus arteriosus to oxygen which closes it
Additionally, decreased prostaglandins allow the DA to close
What is the risk of the foramen ovale staying open?
PFO increases the risk of a paradoxical embolism to the brain (not lungs)
What drugs can open the ductus arteriosus? Close it?
Close - indomethacin
Open - Prostaglandin E1
How is PVR calculated?
How is SVR calculated?
How does hypercarbia/hypocarbia affect PVR?
Hyper - Increases
Hypo - Decreases
How does hypoxemia affect PVR?
Increases
How does acidosis/alkalosis affect PVR?
Acidosis - Increases
Alkalosis - Decreases
How does pain and light anesthesia affect PVR?
Increases
How does hypothermia affect PVR?
Increases
How does vasoconstrictors/dilators affect PVR?
Constriction - Increases
Dilation - Decreases
How does Trendelenburg and collapsed alveoli affect PVR?
Increases
How does anxiety affect SVR?
Increases
How does histamine and anaphylaxis affect SVR?
Decreases
What is a R to L shunt called? What happens?
A cyanotic shunt
Venous blood bypasses the lungs
Examples of cyanotic shunt?
5 T’s
- Tetralogy of Fallot
- Transposition of great arteries
- Tricuspid abnormality
- Truncus arteriosus
- Total anomalous pulmonary venous connection
What is the most common cyanotic shunt?
Tetralogy of Fallot
What are the hemodynamic goals of R-L shunt?
Maintain SVR and Decreases PVR
What is a L to R shunt called?
Acyanotic shunt where blood from the left side recirculates through the lungs
Most common acyanotic shunt? Other examples?
Ventricular septal defect
Atrial septal defect
Patent ductus arteriosus
Coarctation of aorta
Hemodynamic goals of L to R shunt?
Avoid increased SVR
Avoid decreased PVR
L-R shunt, slower or faster inhalation induction?
Minimal effect
R-L shunt, slower or faster inhalation induction?
Slower induction
L-R shunt, slower or faster IV induction?
Slower induction
R-L shunt, slower or faster IV induction?
Faster induction
What is Eisenmenger syndrome?
When a patient with L-R shunt develops pulmonary HTN and reverses flow which now causes a R-L shunt
What are the 4 defects with tetralogy of Fallot?
- RV outflow tract obstruction
- RV hypertrophy
- Ventricular septal defect
- Overriding aorta because it’s receiving blood from both ventricles
What is Tet spell?
Increased sympathetic activity which increases myocardial contractility thus leading R to L shunt and hypoxemia
Who can experience Tet spells? Examples of how they occur?
Children with unrepaired tetralogy of Fallot
-Crying
-Agitation
-Pain
-Pooping
-Trauma
-Scared
How do children try to treat Tet spells on their own?
Squat and bear down which increase SVR and blood flow thus restoring blood flow
How does anesthesia treat Tet spells?
-100% FiO2
-Increased Volume
-Phenyl to increase SVR
-Reduce SNS
-Knee to chest position
What does anesthesia avoid with Tet spells?
Inotropes because of an increased RVOT obstruction
High airway pressures
Goals for tetralogy of Fallot?, SVR, PVR, HR, Contractility, Preload?
SVR - Increase
PVR - Decrease
HR - Maintain
Contractility - Maintain
Preload - Increase
Best drug for induction of tetralogy of Fallot?
Ketamine
1-2mg IV
2-4mg IM
Most common congenital anomaly in infants/children and adults?
Infants/Children - VSD most close by 2 years old
Adult - Bicuspid aortic valve
What is the coarctation of the aorta? What is highly associated with this?
Narrowing of the thoracic aorta
Turner syndrome
Coarctation of the aorta, how is BP affected?
SPB is elevated in UE
SPB is reduced in LE
What is Epstein anomaly?
Congenital defect of the tricuspid valve
SVT is common
R-L shunt
RV failure
Tricuspid regurgitation
What is a fontan completion ?
The patient has a single ventricle that pumps blood into the systemic circulation and no blood to pump into the pulmonary circuit
What do people with fontan completion rely on?
Negative pressure during spontaneous breathing?
Preload dependent
DO NOT let them become dry or use positive pressure ventilation
What is truncus arteriosus?
A single artery that rives rise to the pulmonary, systemic, and coronary circulations
Cardiac circulation in adults? Fetus? Series or Parallel?
Adult - Series
Fetus - Parallel
How does Nitric Oxide effect PVR?
Decreases
How does hemodilution effect PVR and SVR?
Decreases both
RV hypertrophy causes what type of axis deviation?
Right axis deviation
Which drugs should be avoided in the patient with tetralogy of Fallot?
Drugs that have histamine release
Inotropes
Which drugs have histamine release?
Morphine
Meperidine
Atracurium
Why are some patients with tetralogy of Fallot polycythemic?
Because the chronic hypoxemia stimulates RBC production
What is a Tet Spell?
Increased SNS activity causes an increase in myocardial contractility and causes RVOT
Management of PVR for tet spells?
Avoid increase
Management of SVR for tet spells?
Increase
Management of Contractility for tet spells?
Maintain
Management of HR for tet spells?
Maintain
What is the most common VSD type?
Peri membranous
What is the most common ASD type?
Secundum which is in the middle of the atrial septum
What is the most common congenital defect in children?
VSD
Should antibiotics be given for a VSD?
No - only within 6 months of surgical repair
When does the VSD usually close by?
2
What is the biggest concern for VSD? Which disease?
Eisenmenger’s
When the L-R shunt turns into a R-L shunt because of high PVR
PVR and SVR management for a VSD?
Avoid increased SVR and avoid decreased PVR
What is an early symptom of ASD?
Poor exercise tolerance
Best site to monitor arterial BP during the repair of coarctation of aorta?
R arm because left subclavian maybe narrowed thus causing reduced perfusion to the ULE
Treatment for severe obstruction of coarctation of the aorta?
Need to keep a patent ductus arteriosus to prevent hemodynamic collapse
In severe coarctation of the aorta, what does the lower body rely on for perfusion?
A patent ductus arteriosus
What are 2 cardiac signs of coarctation of the aorta?
Systolic BP is greater in the upper extremities vs the lower extremities
Differential cyanosis
What is the most common single ventricle lesion?
Hypoplastic left heart syndrome
What is Ebstein’s anomaly?
Downward displacement of the tricuspid valve
How is IV induction affected by Ebstein’s anomaly?
Slower due to pooling of drugs
Common rhythm with Ebstein’s anomaly?
SVT
Tricuspid regurg or stenosis with Ebstein’s anomaly?
Regurg
