Download (Microsoft PowerPoint - Poporodn\355 adaptace_MP_A_def)

Fetus – birth
• During delivery "asphyxia“ is certain
The postpartum adaptation
• Compensatory mechanisms:
– Higher affinity of hemoglobin to oxygen
– Shunting of oxygenated blood to the vital
organs (heart and brain)
– Fast tissue perfusion (high HR)
Childbirth: changes of an
environment
• Water
•
•
•
•
Quiet
Darkness
Optimally warm
Protected
→ Air
→ Loud
→ Lightened
→ Cold
→ Unprotected
• Gravitation ⇒ effect on the locomotor system
• Stress reaction ⇒ epinephrine, norepinephrine,
ACTH, cortisol
The postpartum changes
• Immediate:
– first breath
– circulatory changes
• Slower changes:
– liver
– hemoglobin
– kidneys
Catecholamines
• Potentiate the absorption of fluid from the
bronchi
• Potentiate secretion and release of surfactant
• Mobilize of endogenous energy sources and
their utilization
• Activate thermogenesis to protect against cold
• Regulation of circulation in the brain and heart
• Support vigilance – "arousal"
Respiratory system
• Fetal respiratory system:
– 3rd – 16th weeks = terminal bronchioles
– 20th – 22nd weeks = pneumocytes of the 1st and 2nd
types
– 24th week = surfactant (secretion can be increased by
betamethasone)
• Development of alveoli continues after birth
• 5th – 6th year = number of alveoli as in adult –
300 millions (5 times more than at birth)
1
Fetal lungs
• For normal development require the
presence of pulmonary fluid and fetal
breathing movements
• During 22nd – 24th fetal weeks ⇒ adequate
circulation and alveolar gas exchange is
also required
Fetal breathing
• For the development of lungs the following is
necessary:
– Mild contractions of diaphragm
– Sign of abnormal development is presents of chest
and abdominal wall movements that are (more than
30% of time) fast and uncoordinated
(oligohydramnion, hydrothorax, musculoskeletal
disorders, diaphragmatic hernia)
• Gasping during asphyxia (meconium aspiration
hazard)
Fetal pulmonary fluid
Secreted by
1st
type pneumocytes – 135-180 ml/kg /day
Fills the airways and alveoli 30 ml/kg
Secreted only before birth → postpartum
resorption (adrenaline)
Resorption of fluid :
– Is induced by chest compressions (passage via
birth canal)
– Is to lymphatic vessels
First breath
Chest compressions during passage via the birth
canal squeezes fluid from the fetal lung
• Stimuli for the first breath:
–
–
–
–
hypoxia
hypercapnia
arousal
sensory inputs from surrounding
• sounds, touch, cold, pain
• Energy demanding due to:
– Resistance in the airways
– Fluid in the lungs
– Surface tension in the alveoli
(air / water)
NB: Role of NE and Cortisol!!!
First breath
• Opens alveoli
⇒ decreases tension in the wall
(La Place: P = 2T / R)
• Creates TLC, FRC, TV
• The first exhalation is active ⇒ pushes out the amniotic
fluid from the bronchi
• Lung expansion and increased PAO2 ⇒ changes in the
pulmonary circulation ⇒ changes in the systemic
circulation
Respiration in newborns and
infants
• Breathing through the nose mainly, its
resistance is about 40% of the total airway
resistance,
– Dangers of swelling!!!
– Hyperemia!!
• Atresia of choans!!
– Hypoxia is observed already in the delivery
room
2
Respiratory changes
• Energy demanding because
they are very intensive
Fetal circulation
• Pulmonary circulation has high resistance
(↓↓pO2)
• Breathing is periodic
– apnea is less than 5 seconds followed by tachypnoea
• Beware of mother anesthesia!
• Important: lung expansion and increased PAO2
leads to changes in the pulmonary circulation,
which initiate changes in the systemic
circulation
Factors decreasing pulmonary
vascular resistance
•
•
•
•
Mechanical factors
Increase of paO2 and rise of pH
Decrease in paCO2
Increase levels of prostaglandins PGE2,
PGI2
• Placenta has the lowest resistance in the
fetal circulation
• Both heart chambers are equally strong
and pump blood in parallel rather than in
series
• Foramen ovale closes completely at the
age of 5 years in 50% of children
• In 30% of the population it remains open
• Functional closure of the ductus arteriosus
occurs within 60 hours in 93% of healthy
newborns
• Within 4-8 weeks closes completely
Congenital heart defects
ECG
• Fetal circulation:
– Right-sided dominance – 65% of CO
• After the birth:
– During 3rd – 6th months establishes classical
left-sided dominance
• Each year in the Czech Republic about
500 children are born with a heart defect :
The most common congenital heart defects:
•
•
•
•
•
ventricular septal defect (VSD)
atrial defect counter (ASD)
aortic stenosis
pulmonary artery stenosis
transposition of the great arteries (TGA)
•coarctation of the aorta (CoA)
•patent ductus arteriosus (PDA)
•atrioventricular septal defect
•hypoplastic left heart
•Tetralogy of Fallot
• There are number of genetic disorder (chromosome
aberrations) and environmental factors responsible for
the formation of congenital heart defects
• The critical period of heart development influenced
external factors is 2nd to 8th weeks of pregnancy
http://www.kardiochirurgie.cz/vrozene-vady
3
Congenital heart defects
• Without shunt – coarctation of the aorta, valvular
defects
• Shunts with possible cyanosis – some of left-toright shunts
• Cyanotic shunts – right-to-left
• Factors determining the size of the shunt and
direction of flow: pressure gradient, the exact
location
• The consequences of left-right circuit =>
response of pulmonary circulation and shunt
redirection
• The consequences of right-left shunt
Hematologic changes
HbF: α2γ2
HbA: α2β2
• At birth: HbF 70 – 80%
• At 6 months, there is no HbF present
• However, HbA production is not as fast (not
enough Epo)
• Physiological anemia during 8th-10th week
http://pf.lf2.cuni.cz/vyuka/repetitoriumobeh/vrozene_srdecni_vady.html
Liver
• Enzymatic pathways are fully active after
3rd month
• Conjugation of bilirubin is fully active after
2nd week
Hyperbilirubinemia
• Hyperbilirubinemia (regardless the age) defined as more
than 25 umol/l of bilirubin in the blood
• In newborns clinical manifestation of jaundice occur
when the levels of bilirubin raise to 6885 umol/l.
Icterus neonati (physiological neonatal jaundice,
physiological hyperbilirubinemia) occurs in 45-65% of
healthy newborns by the 5th day
• It never occurs within the first 24 hours after birth
• Physiological deficiency of vitamin K
• The rate of increase of total bilirubin in physiologic
jaundice should not exceed 85 umol/l/24hr
Hyperbilirubinemia
• Free, fat-soluble unconjugated bilirubin easily
crosses the blood-brain barrier
• Bilirubin is mostly bounded to albumin, however,
during various pathological conditions (as
asphyxia, acidosis, hypoperfusion,
hyperosmolality, sepsis), the complex freely
moves to the central nervous system
• The exact concentration of bilirubin, which leads
to the development of kernicterus is unknown
Neonatal hyperbilirubinemia (jaundice
pathological) classified on the basis of the
pathophysiological mechanisms that lead to
the accumulation of bilirubin in the tissues into
three groups:
1. increased production of bilirubin,
2. decreased conjugation of bilirubin and
3. pathological excretion of bilirubin
Autor: www.zdn.cz
4
Skin
Termed newborn:
• functionally immature skin
vernix caseosa – waxy substance
coating skin of newborn
• Increased vulnerability - physical, chemical
• Increased water loss
• Decreased anti-infective barrier ⇒ eczema
Temperature regulation in
newborns
Temperature after birth = maternal core temperature
Thermoneutral environment for newborn during the first
week after birth is:
– for naked full-term 32 to 34 º C
– for dressed full-term 24 to 27 º C
• Reaction to cold – non-shivering
thermogenesis (brown fat), vasoconstriction,
restlessness, flexion posture
• Reaction to heat - vasodilatation,
sweating(?), hypoactivity, extension of posture
Thermoregulation
Newborn has 2.5 - 3 times higher body
surface relatively to the body weight than
adults
– Radiation (39%)
– Convection (34%)
– Evaporation (24%)
– Conduction (3%)
– Sweating matures after 26 weeks
Thermogenesis
• Non - shivering thermogenesis
Brown fat is about 6% of weight, located
interscapular but also in mediastinum, axilla,
etc.
• Beware of maternal medication
• Premature child
Tubular function
Glomerular filtration
• Starts functioning between 9th to 12th gestational weeks
• GFR increases with gestational age and during postnatal
age
systemic blood pressure, ↓ vascular resistance in splanchnic
organs
– ↑
• Complete maturation between 5th – 8th week of life (in
immature infants later)
• Activation of cortical glomeruli
• GFR after birth = 1 – 2 ml/min/m2
• At the age of 1 month – 50 ml/min/m2
• Functional immaturity of tubules
– juxtamedullar glomerulus - a shorter loop of Henle
Properties:
⇒ Reduced efficiency countercurrent system
⇒ Reduced sensitivity to regulating hormones
⇒ Reduced concentration and dilution capacity
⇒ ↓ production of calcitriol (Vit D3)
↓ ability to maintain volume and composition of body
fluids
↓ ability to quickly eliminate ionic charge and water
to keep ABB
Tubules maturate during 3rd – 5th month
5
Nota Bene
• Immediate changes:
– First breath, changes in circulation and Hgb
– Apgar score
– Closing of fetal shunts starts immediately after birth and
continues through month-years
– Cyanosis develops easily
Thank you
for your attention
• All organs have low functional reserve (capacity), thus
evry newborn is vulnerable to disturbances which in
addition arise quickly and easily
• Keep in mind critical periods of fetal and development
6