Perinatal Adaptation Flashcards
What are the 3 shunts in the fetal circulation?
ductus venosus; foramen ovale; ductus arteriosus
What is the function of the ductus venosus?
shunts blood from the umbilical vein to the IVC to bypass the liver
What is the function of the foramen ovale?
shunts blood from the right atrium to the left atrium- bypassing the lungs
What is the function of the ductus arteriosus?
connects the proximal pulmonary artery to the descending aorta, allowing blood in the right ventricle to bypass the lungs
What hormones are increased in the fetus at the onset of labour?
increased catecholamines/amines stopping synthessis of lung fluid
What occurs with the circulatory transition in newborns?
pulmonary vascular resistance drops; whilst systemic vascular resistance rises; oxygen tension risese; prostaglandins drop; ductus arteriosus and foramen ovale close
What causes the baby to take their first breath?
their CNS reacting to the change of environment and temperature
What causes the umbilical arteries to constrict and increase the resistance of the placenta?
oxygenated blood
What causes closure of formaen ovale?
increase in pulmonary venous return results in higher left atrial pressure than right
What causes closure of hte ducutus arteriosus?
increased oxygenation; decreased flow through the duct and decreased prostaglandins
What does the ductus venosus become?
ligamentum teres
What does the ductus arteriosus form?
ligamentum arteriosus
What happens in persistent pulmonary hypertension of hte newborn?
persistance of the fetal circulation in the newborn (PFO and PDA) due to pulmonary vascular resistance not reducing as it should, so right-left shunting still occurs resulting in poorly oxygenated blood in the systemic circulation
How is PPHN diagnosed?
pre- and post-ductal oxygen saturations- difference of >10% suggests hypertension
What is the managemtn of PPHN?
ventilation; oxygen; nitric oxide; sedation; inotropes; ECLS
What causes PPHN in term babies?
acidosis and alveolar hypoxia are potent pulmonary vasocontrictors eg sepsis or asphyxia
What is the most common cause of respiratory distressi n newborns?
transient tachypnoea of the newborn
What causes transient tachypnoea of the newborn?
incomplete absorption of the fetal lung fluid after birth
What happens to fetal lung fluid during labour?
progressivley absorbed into the interstital spaces and lympathatics so that lungs can fill with air once born
What is the normal course of transient tachypnoea of the newborn?
fluid is reabsorbed after birth and signs of resp distress improve within 24-48 hours
What is seen on CXR with transient tachypnoea of the newborn?
streaky parenchymal lung opacities and small pleural effusions
What are the 4 methods of heat loss inthe new born?
radiation; convection; evaporation; conduction
What is the main source of heat production in the newborn?
non-shivering thermogenesis
What is non-shivering thermogenesis?
heat produced by breakdown of stored brown adipose tissue in response to catecholamines
Why are neonates are high risk of hypothermia?
large surface area-to-body mass ratio; decreased subcut fat; immature skin- evaporative loss; greater water content; poorly developed mechanisms (no shivering); altered skin flow (peripheral cyanosis )
What is the greatest loss of heat after birth for the neonate?
evaporation of amniotic fluid
What is conduction?
When baby is placed on cold table etc. and heat transfer occurs
Waht is radiation?
When newborn is near cool objects, transfer of heat between surfaces that arent touching
What is convection?
When newborn is exposed to cool surrounding air
Why are SGA and preterm babies at higher risk of hypothermia?
low stores of brown fat; little subcut fat and larger surface area:volume
How is hypothermia avoided in neonates?
get baby dry; hat; skin-to-skin; blanket/clothes; heated matress; incubator
How do neonates compensate for loss of placental glucose infusion?
mobilisation of hepatic glycogen stores for gluocneogenesis and use ketones as brain fuel
What are the reasons for babies developing hypoglycaemia?
increased energy demands; low glycogen stores; inappropriate insluin/glucagon ratio; some drugs
What may cause a baby to have increased energy demands?
unwell or hypothermia
What may cause a baby to have low glycogen stores?
small; premature
Waht is the role of oxytocin in breastfeeding?
milk ejection
What is the difference between colostrum and mature breast milk?
thick, yellowish secretion that is higher in immunoglobulins (IgA) phospholipids; cholesterol and protein and lower in lactose and fact
What causes physiological jaundice?
breakdown of fetal haemoglobin; conjugating pathways are immature resulting in a rise in circulating unconjugated bilirubin
