Extra uterine adaptation

1. Extra uterine adaptation
Dr Etabezahu
May 2023

2. Extra uterine adaptation
• The most complex adaptation in human life
expiriance
• Transition should be successful to survive
• 85 – 90% smooth
• 10-15% delayed and complicated
• Few never achieve

3. Basic Steps in Resuscitation
Rarely Needed
Needed less
frequently
Always
needed
1%
10%
100%
Meds
Chest
compressions
Ventilation with
bag and mask
Dry, warm, clear airway, and
stimulate
Assess baby’s response at birth
3

4. Essential components normal neonatal
transition
 Clearance of fetal lung fluid
 Surfactant secretion & breathing
 Transition of fetal to neonatal circulation
 Decrease PVR & increase pul blood flow
Endocrine supplementation of transition

5. When do we expect abnormalities in
adaptation
 preterm delivery
 c/s delivery

6. 1. Endocrine adaptation
 Primary mediators for transition is cortisol and
catecholamine
 Cortisol
 major regulatory hormone
 Cortisol surge- 30wk- 5-10ug/ml
-36wk- 20
at term- 45
 During labor and few hours after delivery around
200 ug/ml

7.  Function of cortisol
 conversation of T4-T3 increase
 catecholamine release +
 Glucose metabolism pathway in liver
maturation
 B adrenergic receptor density increase in
heart and lung
 Surfactant system induction to maturation

8.  Catecholamine
 Term fetus release NE,E & D from adrenal
medulla
 Preterm secrete more catecholamine b/c
organ system are less responsive

9.  Function of catecholamine
 increase BP following birth
 adaptation of energy metabolism
 Initiation of thermogenesis from brown fat

10.  Thyroid hormone
 The axis mature in late gestation in
association with increase cortisol
 Following term delivery TSH quickly rise &
decrease , T3 &T4 increase
 T3 & cortisol activate NA-K ATPase- help fetal
lung fluid clearance

11. 2. Metabolic adaptation
 Energy metabolism
 Fetal energy- through placenta
 As term approach- glucose stored as glycogen
& fat b/c at birth high insulin level

12.  Thermogenesis
 Fetal body T 0.5 0C higher than maternal T
 Cold stimulus to skin activate brown fat
 Shivering

13. 3. CVS adaptation
The increased cortisol ,cathecolamines,TH,RAS
&vasopressin increase cardiac function and BP
 Major changes
 increase CO
Transition of fetal to adult type circulation

14. Blood Flow Before Delivery
• Blood vessels are
constricted
• Blood flow in the lungs
is decreased
• Blood flow is diverted
across the ductus
arteriosus
Fluid in air sacs
Right
atrium
Right
ventricle
Left
ventricle
8

15.  Why do they need increase CO
 Increase basal metabolism
 Increase work of breathing
Intiation of thermogenesis

16.  Near term CO – 450ml/kg/min
 2/3 RV
 1/3 LV
 Soon after birth LVO & RVO equalized

17.  Organ experiencing increased blood flow
 Lungs
 Heart
 Kidney &
 GI tract

18.  In fetus oxygenated blood from placenta –via
umbilical cord 7 ductus venosus_ IVC_ rt
atrium_ left atrium via FO
 Preferentially to brain and coronary
circulation by fetal left ventricle
 RV is predominant in fetus & most RVO goes
to descending aorta via ductus arteriosis

19. Factors that modulate pulmonary vascular
tone
• Oxygen --- Hypoxemia is a potent vasoconstrictor
• Carbon dioxide ---Hypercapnia increase pulmonary
vascular tone
• Acid-base balance ---acidosis induces pulmonary
vasoconstriction
• Temperature---hypothermia induces pulmonary
vasoconstriction
• Maturity ---PVR decreases with advanced fetal age

20.  Why high PVR in utro
 low O2 tension & low pul blood flow suppress
synthesis of NO & PG I2 from pul endothelium
 With delivery ventilation & oxygenation
increase NO &PG I2 which are vasodilators
pulmonary circulation increase_ functional
closure of ductus begin

21. The use of supplemental O2 for initiation of
ventilation will case rapid decrement of PVR &
rapid increment in pul blood flow.
 Normal O2 saturation of fetus is around 65%
 During labor fetus tolerate as low as 30% with
out acidosis
 After birth – 90% at 5 min of age *

22. 4. Lung maturation
 lung fluid is secreted by airway ephtilium
 Cortisol ,TH &catecholamine increase and
shutdown activated chloride channel and
activate NA-K ATPase.

23. First breath and transition physiology
• Passage through birth canal ---raise intra
thoracic pressure to 60-200 cm H2O
• Express 5-10 ML tracheal fluid through mouth
and nares
• Chest recoil ------air drown in
• Initial inflation pressure -----25-30ML H2O
• Second breath -----less pressure
• Third breath ---- small airways open

24. • Lungs expand
with air
• Fetal lung fluid
leaves air sacs
• Fluid replaced by
air in air sacs
Alveolar fluid replaced by air following
breathing at Birth
9

25. Normal Transition
• No meconium
• Breathing/crying
• Good muscle tone
• Term
12

26. Abnormal Transition
• Gasping, ineffective or no breathing
• Poor muscle tone
• Central cyanosis (blue)
• All need assisted ventilation! 13