Neonatology Flashcards
What is the definition of a neonate?
Infant <28 days old
How does the cardiopulmonary circulation work in the foetus?
- Lungs filled with fluid and oxygenated blood which is provided by the umbilical vein from the placenta
- Blood bypasses foetal liver via ductus venosus into the IVC which drains into the R atrium
- Pulmonary vasculature remains constricted = high pulmonary vascular resistance therefore blood bypasses the lungs and travels straight from R atrium into aorta via ductus arteriosus and via foramen ovale (into the L atrium–> Lv ventricle –> aorta)
- Deoxygenated blood then flows to placenta via two umbilical arteries
What happens to cardiopulmonary circulation during birth?
- During descent the foetal chest is squeezed as it passes through pelvis - causing some of the lung liquid to be drained
- Multiple stimuli e.g. thermal and tactile initiate breathing
- First breath causes remaining fluid in the lung to be absorbed into the lymphatic and pulmonary circulation
- This increase in pulmonary circulation leads to fall in pulmonary resistance, allowing blood from R atrium to flow though pulmonary vasculature into L atrium
- This causes rise in L atrial pressure which leads to closure of the foramen ovale
- Flow of oxygenated blood through ductus arteriosus leads to closure
What is the role of surfactant?
- Decreases surface tension so the alveoli do not collapse on expiration
- Increases compliance of the lungs so they can expand further to take in more oxygenated air
Why can C-section babies have problems breathing?
They do not have the same compression on the chest which squeezes out the fluid in the lungs during descent in vaginal delivery.
It can take hours for fluid to be reabsorbed by the lungs, leading to rapid and laboured breathing.
What three things are key for a neonate during their first few hours?
- Taking their first breath and crying - both these things will ensure that fluid from the lungs are removed, therefore preventing collapse of the airways, allowing the pulmonary vasculature to function
- Thermoregulation - neonates cannot thermoregulate well. They have a large SA and are initially covered in fluid so the evaporation makes them colder.
- Feeding - need suckling reflex and ability to swallow to begin feeding to meet their large energy demands.
What do neonates get when they are born?
- Vitamin K - prevent haemorrhagic disease of the newborn
- Newborn baby check - eyes, heart, genitalia and hips
- Heelprick test
- APGAR score - 1 min and 5 mins
APGAR score components…
APGAR:
- Activity (muscle tone)
- Pulse (heart rate)
- Grimace (reflex irritability )
- Appearance (colour)
- Respiratory effort
Score:
7-10 = healthy
4-6 = moderate depression 0-3 = severe depression
Causes of birth asphyxia …
- Prolonged labour
- Deprivation of oxygen in-utero
- Birth trauma
- Maternal anaesthetics/ analgesia
- Prematurity
- Lung malformation
Basic principles of neonatal resuscitation…
- If baby does not take first breath, they need to be transferred onto resus trolley with overhead heater present to keep them warm
- If breathing is irregular - respiratory manoeuvres are done
- If heart rate has fallen - lung inflation is by mask ventilation
- Tracheal intubation may be required
- HR <60 is considered an arrest and chest compressions should be started
What are the different categories of birthweight?
Small for gestational age (SGA): <10th centile
Low birth weight: <2500g
IUGR = failure to meet growth potential (determined by genetics and environment)
What are the two types of growth restriction, and what are their causes?
Symmetrical = the head circumference, height and weight are all equally reduced
Usually occurs early in pregnancy, caused by: chromosomal syndrome, substance abuse, malnutrition
Asymmetrical = weight and abdo circumfeence are on lower centiles than head circumference. Often occurs later in pregnancy when placenta cannot provide adequate nutrition, due to pre-eclampsia, multiple pregnancy, smoking.
*This is known as head sparing - in an environement of limited nutrients, the foetal blood supply will reroute blood to the brain to ensure it grows normally, at the expense of the rest of the body.
How often is a growth scan required for IUGR infants…
Every 2 weeks following 28/40:
- Foetal head circumference
- Foetal abdo circumference
- Femur length
- Liquor volume
- Uterine artery dopple
- Uterine artery doppler
Risks due to IUGR…
- Hypoglycaemia
- Hypothermia (due to large SA)
- Preterm delivery
- Polycythaemia (due to hypoxic drive producing more RBCs)
- Neonatal jaundice
- Asphyxia
What is the definition of LGA, and what are the causes?
LGA = large for gestational age - >90th centile for gestation
Causes: GDM, pre-existing diabetes, Bekwith -Wiedemann syndrome (overgrowth disorder)
