Week 3- Neonatology Flashcards
what is a neonate considered?
<30 days
What is newborn considered?
<24 hrs
Why is fetal circulation different?
- The lungs are not mature enough to enable gas exchange
- Babies are not breathing in utero, therefore the neonate relies on placenta, which connects maternal/ fetal circulation
Where does the gas exchange happen in fetal circulation?
- Gas exchange occurs in the placenta
What is preferential streaming?
- Cardiovascular system is adapted to ensure the most highly oxygenated blood is delivered to the myocardium and brain
Oxygenated blood passes thru…
- via 1 umbilical vein to the fetus
Deoxygenated blood is carried…
- via 2 umbilical arteries
Ductus Venosus
- continuation of umbilical vein, which by passes most of the blood from the liver and connects the umbilical vein to the inferior vena cava
Foramen Ovale
- shunt (opening in septum) allows blood to travel from the right atrium to the left atrium
Ductus Arteriosus
- artery that joins pulmonary system directly to aorta
What is fetal circulation before birth?
- O2 and nutrients from maternal blood transferred from placenta thru umbilical vein and most of the blood bypasses immature live via the ductus venous into inferior vena cava
- Oxygen rich blood travel into RA (greater pressure between atrias) of the heart thru the foramen ovale to the left atrium (approx 2/3 of O2 rich blood)
- Superior vena cava brings deoxygenated blood also into RA, therefore there is mixing of oxygenated & deoxygenated blood in the RA of the fetal heart
- From the LA, blood is transferred to the LV into coronary arteries and aorta where oxygenated blood is delivered to the brain as well as kidneys, lungs
- Some blood in the RA will pass into the RV where it will transfer into pulmonary artery, but bc alveoli are fluid filled most of the blood is shunted away from the lungs via the ductus arteriosus, into aorta due to the pressure imbalance.
- Deoxygenated blood enters systemic circulation and is then carried back to placenta via the umbilical arteries where the blood can be oxygenated and the cycle can occur again
What is the fetal circulation after birth?
- After birth, and cord cutting, the neonate will support itself under normal circumstances
When the baby takes it first breath:
- The surface tension that collapses the alveoli in uteri is now broken allowing the opening of the alveoli, and spontaneous oxygenation/ respiration
Pulmonary resistance decreases and the blood flow from the placenta stops
- The pressure in left side of heart becomes greater than the right when the fetus was in utero
Pressure in aorta; left side of the heart increase systemic vascular resistance
- Pressure changes the fetal shunts close within the first few hours of birth
What are the 3 major physiological changes involved post delivery?
- Ventilation
- Hemodynamics
- Temperature regulation
Physiological changes- ventilation
- Due to the compression of neonate during vaginal delivery fluid is forced from the lungs into the nose/ mouth. Once delivery has occured to lungs are inflated with the first breath; which establishes function residual capacity within the lungs; this allows gas exchange to occur. If it doesn’t in can be reproduced with artificial ventilation (BVM)
Physiological changes- hemodynamics
- as the pulmonary vascular resistance decreases as the lungs are not functioning blood flow increases, and is able to carry oxygen throughout the body
Physiological changes- temperature regulation
- Due to large surface area, immature regulation and little fat, neonates are at risk of hypothermia and compensate with vasoconstriction and an increase metabolism
What are some examples of simple heart defects?
- Atrial and ventricular, septal defects
- Patent ductus arteriosus
- Pulmonary stenosis
What is an example of critical condition heart defects?
- The tetralogy of fallot
Babies born with this or another critical congenital heart defect typically have low levels of oxygen soon after birth and need surgery within the first year of life
What is atrial septal defect?
- A hole in the wall between the left and right atria
- The hole causes blood flow from the LA and mix the RA, instead of going to the rest of the body
Why is atrial septal defect considered a simple congenital heart defect?
- b/c the hole may close on its own as the heart grows during childhood
What is ventricular septal defect?
- Is a hole in the wall between the left and right ventricles
- Blood may flow from the LV and mix with blood in the RV, instead of going to the rest of the body
- If the hole is large, the heart and lungs may need to work harder to pump blood. In addition, it may cause fluid to build up in the lunhs