Perinatal Adaptation Flashcards
What are the functions of the placenta?
Foetal homeostasis, gas exchange, nutrient transport, acid-base balance, hormone production, transport of IgG
What are the three shunts of the foetal circulation?
Ductus arteriosus, ductus venosus, foramen ovale
How much of the output from the heart goes to the lungs in the foetal circulation?
7% of output goes via lungs
How does the foetus prepare itself for birth in the third trimester?
Surfactant production and swallowing of amniotic fluid
Accumulation of glycogen, brown fat and subcutaneous fat
What foetal changes occur during labour and delivery?
Increased catecholamines/cortisol at onset of labour
Synthesis of lung fluid stops
What does a vaginal delivery achieve?
Squeezes lungs to get rid of fluid
What occurs during the circulatory transition after birth?
Pulmonary vascular resistance drops and systemic vascular resistance rises
Oxygen tension rises and circulating prostaglandins drop
Duct constricts and foramen ovale closes
What are the fates of the foetal shunts?
Foramen ovale = closes or persists as PFO (10%)
Ductus arteriosus = becomes ligamentum arteriosus, may persist as PDA
Ductus venosus = becomes ligamentum teres
What is the underlying pathophysiology of persistent pulmonary hypertension of the newborn?
Failure of the foetal circulatory system to adapt = more common in term infants
What causes hypoxaemia in persistent pulmonary hypertension of the newborn?
Secondary to extrapulmonary shunting of blood from right to left via patent ductus arteriosus and foramen ovale
What are the risk factors for persistent pulmonary hypertension of the newborn?
Meconium aspiration, pneumonia, congenital diaphragmatic hernia
What are the symptoms of persistent pulmonary hypertension of the newborn?
Grunting, cyanosis, low oxygen saturation and BP, tachycardia and tachypnoea
How is persistent pulmonary hypertension of the newborn diagnosed?
CXR, echo, pulse oximetry, ABG
How is persistent pulmonary hypertension of the newborn treated?
Ventilation, oxygen, nitric oxide, sedation, inotropes, extracorporeal life support (ECLS)
What are the issues with thermoregulation in newborns?
Large surface areas, wet when born, no shivering, peripheral vasoconstriction
What is the main source of heat for newborns?
Non-shivering thermogenesis
How do newborns perform non-shivering thermogenesis?
Heat produced by breakdown of stored brown adipose tissue in response to catecholamines = not effective in first 12hrs of life
Why are small for date and preterm babies more likely to struggle with thermoregulation?
Low stores of brown fat, little subcutaneous fat, larger surface area to volume ratio
How can hypothermia be prevented in a newborn?
Dry baby, hat, skin-to-skin contact, blanket/clothes, heated mattress, incubator
Why do newborns struggle with glucose homeostasis?
Interruption of glucose supply from placenta
Very little oral intake of milk
What happens to newborns after birth in relation to glucose homeostasis?
Drop in insulin and increase in glycogen
Mobilisation of hepatic glycogen stores for gluconeogenesis
What can newborns use as brain fuel in place of glucose?
Have ability to use ketones as brain fuel
What are the risk factors for hypoglycaemia?
Increased energy demand = illness, hypothermia
Low glycogen stores = small for date, premature
Inappropriate insulin to glycogen ratio = maternal diabetes, hyperinsulinaemia
What reflex is triggered when a baby starts to suckle?
Rooting and Suck reflex = feedback loop causes increase in supply
How does the composition of breastmilk change over time?
changes from colostrum to foremilk and hindmilk
Why does foetal haemoglobin become disadvantageous?
Increase in 2,3 BPG shifts curve to right
Where does haematopoiesis move to after birth?
Bone marrow
Why does physiological anaemia occur in newborns?
Adult haemoglobin synthesised more slowly than foetal haemoglobin is broken down = lowest at 8-10 weeks
Are liver enzyme pathways present in newborns?
Yes, but they are immature
What occurs in physiological jaundice?
Breakdown of foetal haemoglobin = conjugating pathways immature, rise in circulating unconjugated bilirubin, not harmful unless very high levels
When may jaundice in a newborn be pathological?
If it occurs early or is prolonged
What are the risk factors for adaptation problems?
Hypoxia or asphyxia during delivery
Particularly small or large babies, and premature babies
Ill babies = sepsis, congenital anomalies
