Congenital heart disease Flashcards
What is the organ of respiration in the fetus?
the placenta
How is the circulation arranged in the fetus?
parallel (adults is in series)
Describe SVR and PVR in the fetus?
SVR- low
PVR- high
What kind of shunting occurs in the fetus?
right-to-left shunting across the foramen ovale and ductus arteriosus
Describe the umbilical vein and artery of the fetus.
one umbilical vein that carries oxygenated blood from the mother to the fetus
two umbilical arteries that carry deoxygenated blood from the fetus to the mother
The fetal circulation is ________ dependent
shunt
Shunts in the fetus are
beneficial in utero but can be problematic during extrauterine life
___________ shunts blood from the right atrium to the left atrium bypassing the lungs
foramen ovale
__________ shunts blood from the umbilical vein to the IVC bypassing the liver)
ductus venous
________________ shunts blood from the pulmonary artery to the aorta (bypassing lungs)
ductus arteriosus
What is pulmonary blood flow like in the fetus?
minimal
A ductus arteriosus that remains open produces a
systolic and diastolic murmur
Describe what happens in the lungs with the first breath.
lung expansion–> increased PaO2 and decreased PaCO2–> decreased PVR
What leads to an increased SVR for the neonate.
the placenta separates from the uterine wall (or cord clamp)
What occurs with a decreased PVR and increased SVR for the neonate?
LA pressure> RA pressure–> the flap valve of the foramen ovale closes
What causes closure of the ductus arteriosus?
decreased circulating PGE1 (released from the placenta)
decreased PVR–> reversal of blood flow through the ductus arteriosus–> exposes the DA to increased PO2
When does the foramen ovale close?
3 days
What leads to closure of the foramen ovale?
LAP>RAP (umbilical cord clamping–> increased SVR)
A patent foramen ovale leads to the risk of
paradoxical embolism (the embolus travels to the brain instead of the lungs)
When does the ductus arteriosus close?
several weeks via fibrosis
A patent ductus arteriosus can be closed with
indomethacin, a prostaglandin synthase inhibitor
A patient ductus arteriosus can be opened with
prostaglandin E1 (PGE1)
Which conditions increase pulmonary vascular resistance? (select 3)
a. light anesthesia
b. Trendelenburg position
c. alkalosis
d. nitric oxide
e. anemia
f. hypercarbia
a. light anesthesia
b. Trendelenburg position
f. hypercarbia
Conditions that increase PVR include
hypercarbia
hypoxemia
acidosis
atelectasis
Trendelenburg position
hypothermia
vasoconstrictors
light anesthesia
pain
_____________ occurs when there is abnormal communication between the pulmonary and systemic circulations.
Shunting
The size and direction of the shunt are dependent on
three factors
The following influence the size and direction of the shunt:
- ratio of the PVR to SVR
- pressure gradients between the cardiac chambers or vessels involved
- compliances of the cardiac chambers
Conditions that decrease PVR include
hypocarbia
adequate oxygenation
alkalosis
nitric oxide
hemodilution
Conditions that increase SVR include
vasoconstrictors, fluid bolus, and increased SNS tone
Conditions that decrease SVR include
volatile agents
propofol
histamine
hemodilution
sepsis
When does a right to left shunt occur?
when PVR is greater than SVR
When does a left to right shunt occur?
when SVR is greater than PVR
Which congenital defects are MOST likely to cause hypoxemia? (select 3).
a. tetralogy of Fallot
b. ventricular septal defect
c. patent ductus arteriosus
d. coarctation of the aorta
e. Eisenmenger’s syndrome
f. Ebstein’s anomaly
a. tetralogy of Fallot
e. Eisenmenger’s syndrome
f. Ebstein’s anomaly
What are the two types of shunts?
cyanotic shunt (R to L)
Acyanotic shunt (L to R)
Cyanotic shunts include:
Five t’s: tetralogy of fallot
transposition of the great arteries
Tricuspid valve abnormality (Ebstein’s anomaly)
truncus arteriosus
total anomalous pulmonary venous connection
Acyanotic shunts include:
ventricular septal defect
atrial septal defect
patent ductus arteriosus
coarctation of the aorta
A right to left shunt is associated with a ____________ inhalation induction and a ___________________ IV induction
slower; faster
A left to right shunt has ___________________ inhalation induction and _____________________ IV induction
negligible effect on the rate of; possibly prolongs the onset of an
______________________ is when a left-to-right shunt changes to a right-to-left shunt secondary to pulmonary hypertension
Eisenmenger syndrome
A right to left shunt leads to
decreased pulmonary blood flow
hypoxemia
LV volume overload
LV dysfunction
Hemodynamic goals of a right to left shunt include
maintain SVR
decrease PVR- hyperoxia, hyperventilation, avoid lung hyperinflation
A left to right shunt leads to
decreased systemic blood flow- low cardiac output, hypotension
high pulmonary blood flow- pulmonary hypertension, RVH
Hemodynamic goals of a left to right shunt include
avoid increased SVR
avoid decreased PVR by avoiding alkalosis, hypocapnia, high FiO2, vasodilators
Consequences of increased pulmonary blood flow include
ventricular hypertrophy
volume overload of both ventricles–> biventricular failure
biventricular failure
decreased lung compliance + increased airway resistance
pulmonary hypertension
