Adaptation at Birth Flashcards
what are the functions of the placenta
fetal homeostasis gas exchange nutrient transport to fetus waste product transport from fetus acid base balance hormone production transport of IgG
what does the fetal liver do
produces albumin, clotting factors and RBCs
what does the fetal kidney do
excretes urine, contributes to amniotic fluid
describe the fetal circulations
The oxygenated blood is carried from the placenta to the fetus via the umbilical vein. About half of this blood passes through the hepatic capillaries and the rest flows through the ductus venosus into the inferior vena cava. Blood from the vena cava is mostly deflected through the foramen ovale into the left atrium, then to the left ventricle, into the ascending and descending aorta to supply to the fetus
goes back to placenta via the pulmonary arteries (branches of descending aorta)
Deoxygenated blood from the superior vena cava flows into the right atrium, right ventricle, and then into the pulmonary artery. Because of high pulmonary vascular resistance, only about 5 to 10 per cent of the blood in the pulmonary artery flows to the lungs, the majority of it being shunted through the patent ductus arteriosus and then down the descending aorta
name the three shunts in the fetal circulation and what they allow
ductus venosus (allows umbilical vein to pass through liver) foramen ovale (right to left shunt in heart, reduced blood going to lungs) ductus arteriosus (reduces blood going to lungs, mean oxygenated and deoxygenated blood mix in descending aorta)
what does the fetus do in the 3rd trimester to prepare for birth
produce surfactant
accumulation of glycogen - liver, muscle, heart (to prepare for starvation state)
accumulation of brown fat- between scapular and around internal organs (insulating fat)
accumulation of subcutaneous fat
swallowing amniotic fluid and ‘practise breathing’
where is surfactant produced
type 2 pneumocytes in alveoli
what is the role of surfactant
needed for gas exchange
reduces surface tension of alveoli allowing them to expand
what adaptations happen to the fetus during labour
increased catecholamine and cortisol at the onset of labour
synthesis of lung fluid stop
during vaginal delivery lung fluid gets squeezed out
first cry helps absorb left over fluid into lymphatic system
what colour do babies come out
blue/ pale
gradually goes pink after starts to breath/ cry
why is delayed cord clamping important
allows blood volume and immunoglobulin transfer to baby, helps prevent amaemia
what happens to the circulation after birth
pulmonary vascular resistance drops (onset of breathing expands and aerates the lungs)
systemic vascular resistance rises (cord clamped, placenta =low resistance vascular bed removed)
oxygen tension rises (pO2 rises from 2-3.5 kPa to 9-13kPa)
duct (venosus and arteriosus) constricts
foramen ovale closes
what is the fetal level of oxygen (pO2)
2-3.5 kPa
what causes duct constriction in fetal adaptation
increased pO2 (muscle layer is oxygen sensitive)
decreased flow of blood
decreased prostaglandins
when does the ductus close
physiological closure within first few hours/ days
anatomical closure within 7-10 days
what happens to the foramen ovale
closes or persists as PFO (10%)
what happens to the ductus arteriosus
becomes ligamentum arteriosus or persists as duct
what happens to the ductus venosus
becomes ligamentum teres
what can cause failure of cardiorespiratory adaptation
asphyxia (causing hypoxia/ acidosis) prematurity sepsis hypoxia (meconium aspiration) cold stress
what is persistent pulmonary hypertension of the newborn
when lung vascular resistance fails to fall meaning the shunts stay open (right to left flow at PFO and PDA)
Any oxygenated blood comes back into La however PFO and PDA means the oxygenated blood mix with deoxygenated meaning majority of circulation will be deoxygenated blood
what direction of flow in the shunts
right to left
what can cause persistent pulmonary hypertension
asphyxia (causing hypoxia/ acidosis) prematurity - lack of surfactant sepsis hypoxia (meconium aspiration) cold stress
what is a way of diagnosing PPHN
compare oxygenation of blood in right upper limb to left lower limb
branches that supply the right upper limb are pre ductal (will receive oxygenated blood) where as branches to other three limbs are post ductal (will be deoxygenated)
anything more than 3% difference = PPHN
what is the management for PPHN
ventilation
oxygen
nitric oxide (given through ventilator, dilates pulmonary arteries to decreased vascular resistance)
sedation (so dont breath against ventilator)
inotropes (cardiac contractility will be impaired)
ECLS- membranous oxygenation, very invasive, only done in glasgow
what is the presentation of transient tachypnoea
usually healthy babies born by c section
tachypnoeic
can grunt
is transient
a diagnosis of exclusion, will have fluid in horizontal fissure on x ray
what causes transient tachypnoea
baby taking longer to absorb fluid in lungs - eg not squeezed out when birth via c section
why do babies loose so much heat
large surface area wet and naked when born big head if premature will have very thin epithelial layer - more evaporation have no shivering mechanism
what are the 4 ways babies loos heat
convection
evaporation
conduction
radiation
how do babies thermoregulate
non shivering thermogenesis:
-heat produced by breakdown of stored brown adipose tissue in response to catecholamines
-not efficient in first 12 hours of life
=peripheral vasoconstriction
what temperature should you aim for babies to be
36-5 to 37.5
what is acrocynosis
when hands a feet of baby stay blue for a couple days- is normal, heat is important to fix it though
what are small for dates/ preterm babies at higher risk of hypothermia
low stores of brown and subcutaneous fat
larger surface area to volume ratio
thin epithelial layer
how do you prevent hypothemia in babies
dry hat skin to skin blanket/ clothes heated mattress incubator
how do neonates maintain glucose homeostasis
interruption of glucose from placenta + little oral intake of milk= drop in insulin and increase in glycogen
mobilisation of hepatic glycogen stores for gluconeogenesis
ability to use ketones as brain fuel
what can cause hypoglycaemia in a neonate
increased energy demands:
- unwell
- hypothermia
low glycogen stores:
- small/ premature
- high circulating maternal glucose
inappropriate insulin/ glucagon ration:
- maternal diabetes
- hyperinsulinism
some drugs
how do you avoid/ treat hypoglycaemia
identify those at risk
feed effectively
keep warm
monitor
what is the difference between foremilk and hindmilk
foremilk has more glucose, water and antibodies
hindmilk has more protein, fat and calories
what does the suckling stimulus cause in breastfeeding mothers
posterior pituitary releases oxytocin = milk ejection
anterior pituitary releases prolactin= milk production
what does colostrum contain
IgA, cellular immunity, growth factors
is weight loss normal after birth
up to 10% normal - due to fluid loss
what is the risk of dehydration in babies
hypernatraemia
usually due to delayed lactation
how is fetal haemoglobin different from adult
higher affinity
lower oxygen delivery power
what does increased 2,3 BPG do to Hb oxygen curve
shifts it to the tight
what causes physiological anaemia
adult Hb synthesised more slowly than fetal Hb is broken down
causes a physiological anaemia - lowest level at 8-10 weels
what does good recticulocyte (immature red blood cells) levels in babies mean
bone marrow working (haematopoiesis)
what causes physiological jaundice
breakdown of fetal haemoglobin
Conjugating (liver enzymes) pathways immature
Rise in circulating unconjugated bilirubin
not harmful unless very high levels
what suggests jaundice is pathological
if early (<24 hrs) or prolonged
what is the treatment for jaundice
phototherapy (blue light converts unconjugated bilirubin into excrete-able form and is peed out)
if severe exchange transfusion
what might very high levels pf unconjugated bilirubin cause
cross BBB, goes to basal ganglia and can cause significant cerebral changes leading to cerebral palsy
what babies are most at risk of adaptation problems
Hypoxia / asphyxia during delivery Particularly small or large babies Premature babies Some maternal illnesses and medications Ill babies – sepsis, congenital anomalies
