Perinatal Adaptation Flashcards
What is the function of the placenta?
Foetal homeostasis Gas exchange Nutrient transport Waste product transport Acid base balance Hormone production (prepares for labour) Transport of IgG
Describe the foetal circulation
- Oxygenated blood from placenta
- Umbilical vein
- Ducuts venosus in liver
- IVC
- Foramen ovale
- Left ventricle and aorta
- Right ventricle
- Ducuts arteriosus and aorta or pulmonary vein to lungs
What does deoxygenated blood leave by?
Umbilical arteries
During the third trimester how does the baby prepare for birth?
Surfactant production (reduce surface tension to aid gas exchange)
Accumulation of glycogen (ready for starvation state)
Accumulation of brown fat (insulating internal organs)
Accumulation of subcutaneous fat (insulation)
Swallowing/inhaling amniotic fluid (fills lungs to aid growth)
How does the baby respond to labour to aid delivery?
Increases catecholamines/cortisol to prepare for stress
Synthesis of lung fluid stops
Vaginal delivery - lungs squeeze to get rid of fluid
How much fluid is lost by lung squeezing?
30%
How does the baby lose most of the fluid?
Crying - 70% is lost by absorption of fluid to lymphatics
In the first few seconds of life how does a baby adapt to the new world?
Comes out blue, starts to breath and cry, gradually goes pink (oxygenation), cord cut
What does a delay in cord cutting allow?
Blood volume to increase and transfer of immunoglobulins
Describe cardiorespiratory adaptation after birth
- PVR drops while SVR rises
- Back pressure slows flow across foramen ovale and ductus arteriosus (blood flows more easily to lungs)
- Oxygen tension rises
- Prostaglandins decrease to contract ducts and close foramen ovale
What do the two foetal ducts become?
ductus arteriosus - ligamnetum arteriosus
ductus venosus - ligamentum teres
What can failure of cardiorespiratory adaptation lead to?
Persistent Pulmonary Hypertension of the Newborn
Describe the pathogenesis of PPHN
- High PVR as the lungs are solid/no surfactant and will not open
- Oxygenation is minimal and shunts remain open - mixed blood travels to the body
How can you test for an open ductus arteriosus?
Preductal arteries will have higher oxygenation than post ductal arteries - by testing saturation of right hand and one of the feet >3% difference indicates pathology
How is PPHN treated?
Ventilation to give oxygen
Nitric Oxide - dilates pulmonary vasculature to decrease resistance
Sedation - stops the baby breathing against the ventilator
Inotropes - help cardiac function
Extracorpeal membrane oxygenation
Who often presents with transient tachypnoea?
Full term babies born by C -section
How does transient tachypnoea arise?
Lack of lung squeeze (in vaginal delivery) means fluid builds up in the lungs.
What happens to babies with transient tachypnoea?
Usually gets better relatively quickly but requires an infection screening and occasionally respiratory support
Why is it hard for babies to regulate their temperature?
Large surface area (big head)
Wet when they are born (evapouration)
Babies cannot shiver
How is heat lost in babies?
Evaporation
Conduction
Convection
Radiation
Define acrocyanosis
Persistent blue extremities, peripheral vasoconstriction and adapting circulation
What is the ideal temperature range for a baby?
36.5-37.4
How are babies kept warm?
Dried, hat, skin to skin contact, blanket/clothes, heated mattress, incubator
What happens to the glucose levels when a baby is born?
When glucose from the placenta is lost there is a physiological drop in insulin to allow an increase in glycogen - mobilisation of hepatic stores for gluconeogenesis
What can be used as brain fuel in babies - short term?
Ketones
What causes hypoglycaemia?
Increased demand - unwell, hypothermic
Low glycogen stores - small/premature
Inappropriate insulin/glucagon ratio - maternal diabetes/hyperinsulinaemia
Labetalol
Describe the different types of haemoglobin
Foetal Hb has a high affinity for oxygen but is not so good at letting it go. After birth a chemical changes foetal Hb to adult Hb
Where are the two types of haemoglobin produced?
Foetal - liver
Adult - bone marrow
How does anaemia arise in babies?
Adult Hb is synthesised slower than foetal Hb is broken down
How does physiological jaundice occur?
Immature liver enzyme pathways. Breakdown of fetal Hb and immature conjugating pathways leads to increased unconjugated bilirubin
What is the treatment for jaundice in the newborn?
Phototherapy
Exchange transfusion
