The new born and family Adjustment to extra uterine life

The most important physiological change
required from the neonate after birth is the
transition from fetal/placental circulation to
independent respiration.
• The first 24 hours of life are very critical
because respiratory distress or circulatory
failure can occur rapidly with little warning.
• Changes in the various organs/systems
that lead to the adjustment to extra
uterine life include:
Respiratory system:
First respiration is initiated by:
1. Chemical factors: after clamping the
umbilical cord O2 decrease, CO2 increase
and PH decrease, these changes in the
blood initiate impulses that excite the
respiratory center in the medulla.
Thermal stimulus: this is due to sudden
chilling of the infant after delivery the
transfer from the warm uterus to the


cooler atmosphere excite sensory
impulses in the skin that are transmitted
to the respiratory center.
What occurs during the first
breath?
• The air entering into the lungs with the
first breath is faced with the surface
tension of the fluid in the lungs & the
alveoli, this fluid is absorbed via the
lymphatic system & pulmonary capillaries
and part of it is removed by the labor
force
• If delivery was by cesarean section the
lungs will not be compressed to help in
removing the fluid within them &
suctioning has to be done.
• The presence of surfactant helps in
reducing the surface tension in the alveoli
& without this substance the recoiling
characteristic of the lungs will permit any
air exchange to take place.
Initiation of respiration allows blood to
flow through the lungs leading to changes
in the circulation which are due to the
changes in the lungs, heart and major
blood vessels.
The changes are gradual and include:
• Closure of Foramen Ovali (closes
functionally soon after birth)
• Closure of Ductus Arteriosus (closes
functionally by 4th day of life)
• Closure of Ductus Venosus, clamed
(extension of the umbilical cord)
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• The expansion of the lungs causes the
pulmonary vessels to dilate decreasing the
vascular resistance in the lungs so the
pulmonary blood flow increase, so the
pressure in the Rt atrium, Rt ventricle &
pulmonary artery decrease.
• The most important primary factor
controlling ductal closure is the high
concentration of Oxygen level in the
blood.
Secondary factors are:
• Decrease in endogenous prostaglandin
and acidosis
• Murmur may be present because these
changes are gradual and cyanosis may
occur during crying or straining
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Physiological status of other
systems:
• Thermoregulation: It is very important
after establishment of respiration, the
newborn’s heat production is adequate but
there are factors that predispose to heat
loss are:
– Large surface area; this is compensated for by
the flexed position which is the usual position
of the newborn
– The thin layer of subcutaneous fat
Newborns lose heat by four separate mechanisms:
a. convection:الحراري الحمل the Flowing of heat from
the newborn’s body surface to cooler surrounding air.
b. conduction: التوصيلis the transfer of body heat to
a cooler solid object in contact with a baby.
c. radiation: اإلشعاع:is the transfer of body heat to a
cooler solid object not in contact with the baby,
d. evaporation: التبخرis loss of heat through
conversion of a liquid to a vapor.
Hemopoietic system:
The blood volume depends on the time of
clamping of the umbilical cord, which may
increase 100 ml if it is closed after the
cessation of pulsation in the cord. Blood
volume in the full term newborn is 80-
85ml/kg (total is 300ml)
Hemoglobin level averages 17 to 18 g/100 mL
of blood . The Hematocrit is between 45%
and 50%.
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• Fluid & electrolyte balance: at term total
body fluid is 73% (adult 58%). The infant
has higher ratio of extra cellular fluid than
the adult and also higher level of total
body sodium & chloride and lower level of
potassium, magnesium& phosphate.