Educative ppt for students and trainees in Paediatrics, Paediatric Critical care , Neonatology , DCH, DNB Paediatrics

2.  The placenta provides the exchange of
gases and nutrients in the fetus.

3. Four Shunts :
1. The Placenta – 55% of ventricular output and has
the lowest vascular resistance in the fetus.
2. SVC – 15%
3. IVC – 70%
4. The highest partial pressure of oxygen (PaO2) is
found in umbilical vein – 32 mmHg
5. Brain and coronary arteries – receive blood with
higher oxygen saturation PaO2 of 24 mmHg

5.  Lungs receive 15% of combined ventricular
output.
 RV > LV
 RV- 55% LV – 45%

6.  Fetal C.O directly proportional to HR
 Low compliance of Fetal Heart .

7.  Primary change – Shift of blood flow from
placenta to lungs for oxygenation.
 Establishment of Pulmonary circulation

8.  Increase in SVR
 Cessation of blood flow in the umbilical
vein
 Closure of Ductus Venosus

9.  Reduction in PVR
 Increase in Pulmonary blood flow
 Fall in PA Pressure
 Functional closure of foramen ovale
 Increase in LA pressure
 Decrease RA pressure
 Closure of PDA

11. 1.Hypoxia and /or altitude
2. RDS or Congenital Pneumonia
3. Metabolic Acidosis
4. Increased pulmonary artery pressure
secondary to VSD or PDA
5. Increased pressure in the left atrium or
pulmonary vein.

12.  Infants with large VSD may not develop
CHF while living at high altitude, but
develop CHF at sea level.
 In RDS, increase in PaO2 dilates
pulmonary vasculature  resulting in CHF
as baby improves
 CHF does not develop in VSD till 6 to 8
weeks of age or older due to high PA
pressure directly transmitted through LV
pressure.

13.  Functional Closure  10 to 15 hours after
birth by constriction of the medial smooth
muscle in the ductus.
 Anatomic Closure  2 to 3 weeks
permanent changes in the endothelium and
subintimal layers of the ductus.
 Oxygen, PGE2 levels, and maturity of
newborn, acetylcholine and bradykinin are
important factors in the closure of the
ductus.

14.  Strongest stimulus for constriction of the
ductal smooth muscle  postnatal
increase in PaO2 from 25 mmHg to 50
mmHg
 Ductal tissue is less responsive to the
oxygenation changes in premature infant
due to immature ductus and smooth
muscles in the media of ductus.
 High levels of PGE2 in preterm infants.

15.  Decrease in PGE2 levels after birth 
constriction of the ductus
 Constricting effects by indomethacin and
the dilator effects of PGE2 &
Prostaglandin I2 > for premature babies
 Aspirin use in mother  Constricts the
ductus during fetal life  can cause
PPHN.

16.  Increased PGE2
 Reduced arterial PaO2
 Birth Asphyxia
 Hypoxia due to pulmonary diseases
 High altitude

17. PA constricted by
 O2 and Metabolic acidosis
 Epinephrine
 Nor-epinephrine
PA dilated by
 Vagal stimulation
 Isoproterenol
 Bradykinin

18.  Rate at which PVR falls
 Responsiveness of the ductus arteriosus
to oxygen
 High circulating levels of PGE2
 Early onset of a large left to right shunt
and CHF