Fetal and neonatal circulation Flashcards
Where does blood from the placenta travel and what does it bypass?
travels via the umbilical vein passing through the ductus venosus bypassing liver into the IVC
How does 40% of circulating blood in the fetus get from the right atrium to the left?
foramen ovale
What shunt exist to allow for bypassing of blood around the lungs?
ductus arteriosus –both left and right ventricles pump blood to the descending aorta
total CO is from left and right ventricles
How does blood get back to the placenta from the fetus?
descending aorta through hypogastric arteries into the two umbilical arteries into the placenta
What are the four major shunts in fetal circulation?
placenta
ductus venosus
foramen ovale
ductus arteriosus
What triggers the first breath in baby?
hypoxia
hypercapnia
tactile stimuli
cold skin
In the fetus how does the pulmonary resistance/blood flow/and MAP look? What happens at birth?
vascular resistance– high
blood flow– low
MAP– high
Each of these reverses rapidly at birth
What are the 4 functions that the placenta performs?
Lungs-gas exchange
GI- nutrition
Liver- nutrition and waste removal
Kidneys- fluid and electrolyte balance, waste removal
What causes closure of the foramen oval?
reversal of right/left arterial pressure–
increased pulmonary circulation causes increased venous return to the left atrium
Decrease in right atrial pressure
What occurs with the closure of the ductus venosus? How does the closure occur?
portal blood perfuses the liver
Within 3 hrs of birth–constriction of the vascular smooth muscle within the ductus venosus completely occlude the shunt–becoming ligamentum venous
What causes the closure of the ductus arteriosus?
Increased pressure in aorta exceeding pulmonary artery pressure
increased PO2 and decreased circulating prostaglandin cause constriction–bradykinin from the lung is involved
once closed it becomes the ligamentum arteriosum
What occurs if the ductus arteriosus fails to close?
Patent ductus arteriosus–leads to Pul HTN and possibly CHF and cardiac arryhthmias
What is the risk of delivery at high altitude?
Decreased PO2 pressure at high altitudes–PO2 pressure contributes to the closure of the ductus arteriosus
so at high altitudes there is an increased risk of patent ductus arteriosus –this will lead to hypoxia and lung restriction–escalating the problem
What is tetralogy of Fallot?
pulmonary stenosis
dextropostion of the aorta–overriding ventricular septum
RV hypertrophy
VSD
Blue baby syndrome
