Perinatal adaptation Flashcards
What is the function of the placenta?
- foetal homeostasis
- gas exchange
- nutrient transport to foetus
- waste product transport from foetus
- acid base balance
- hormone production
- transport of IgG
What is the function of the foetal liver?
Produces albumin, clotting factors, RBCs
What is the function of the foetal kidney?
Excretes urine, contributes to amniotic fluid
What are the three shunts of the foetal circulation?
- ductus venosus
- foramen ovale
- ductus arteriosus
What happens in the foetus in the 3rd trimester in preparation for birth?
- surfactant production
- accumulation of glycogen- liver, muscle, heart
- Accumulation of brown fat- between scapulae and around internal organs
- accumulation of SC fat
- swallowing amniotic fluid
What happens during delivery to prepare the baby for life?
- onset of labour- increased catecholamines/cortisol
- synthesis of lung fluid stops
- vaginal delivery- squeezes lungs
Describe circulatory transition
- Pulmonary vascular resistance drops
- onset of breathing
- rise in arterial pO2 from 2-3.5kPa to 9-13kPa
- Systemic vascular resistance rises
- cord clamped
- huge, low resistance vascular bed removed
- Oxygen tension rises
- Circulating prostaglandins drop
- Duct constricts
- Foramen ovale closes
How does duct construction occur?
Decreased flow due to decreased pulmonary vascular resistance
Increased pO2- oxygen sensitive muscular layer
Decreased circulating PGE2 due to increased lung metabolism
Shunt becomes bidirectional then left to right
Physiological closure within first few hours/days
Anatomic closure within 7-10 days
What happens to the ductus arteriosus
Closes and becomes ligamentum arteriosus
What happens to the ductus venosus
Closes and becomes ligamentum teres
what happens as a result of failure of cardiorespiratory adaptation?
Asphyxia- hypoxia/acidosis
Prematurity
Sepsis
Hypoxia
Cold stress
What is PPHOTN
Persistent pulmonary hypertension of the newborn
Lung vascular resistance fails to fall
Shunts remain
Right to left flow at PFO
Right to left flow at PDA
How does PPHN present?
Blue baby
big difference between pre and post ductal sats
Sick babies
How should PPHN be managed?
- ventilation
- oxygen
- nitric oxide
- sedation
- inotropes
- ECLS
What is key to the first few hours of life?
- thermoregulation
- glucose homeostasis
- nutrition
What are the 4 mechanisms of heat loss?
- radiation
- convection
- conduction
- evaporation
How do babies thermoregulate
- non-shivering thermogenesis
- heat produced by breakdown of stored brown adipose tissue in response to catecholamines
- not efficient in the first 12 hours of life
- peripheral vasoconstriction
- newborn babies need help
Why are small for dates/preterm babies at risk of hypothermia?
Low stores of brown fat
Little subcutaneous fat
Larger surface area:volume
How can hypothermia be prevented?
- dry baby
- wear hat
- skin to skin
- blanket/clothes
- heated mattress
- incubator
Describe glucose homeostasis after birth
Interruption of glucose supply from the placenta
Very little oral intake of milk
Drop in insulin, increase in glycogen
Mobilisation of hepatic glycogen stores for gluconeogenesis
Ability to use ketones as brain fuel
What causes babies to have increased energy demands?
Unwell
Hypothermia
What causes babies to have Low glycogen stores?
Small/premature
What causes babies to have inappropriate insulin/glucagon ratio?
Maternal diabetes
Hyperinsulinism
How can low glucose levels be avoided?
Identifying those at risk
Feed effectively
Keep warm
Monitor
What weight loss after birth is normal?
10% of body weight
What is hypernatraemic dehydration?
It is a risk when some babies lose more than 10% of their body weight
Usually caused by delayed lactation
When does foetal haemoglobin become disadvantageous?
After birth
There will be an increase in 2,3 BPG and curve will shift to right
What happens after birth regarding Hb?
Haemoatopoesis moves to bone marrow
Adult Hb synthesised more slowly than Fetal Hb broken down
Physiological Anaemia
What causes physiological jaundice of the newborn?
Breakdown of foetal haemoglobin
Conjugating pathways immature
Rise in circulating unconjugated bilirubin
Generally not harmful unless very high levels
What are the risk factors for adaptation problems?
Hypoxia/asphyxia during delivery
Small or Large baby
Premature babies
Maternal illness/medication
Ill babies- sepsis, congenital anomaly
