Introduction to Neonatology Flashcards
What does the CVS begin to form?
Toward the end of the third week
When does the heart start beating?
4th week
When is the critical period for heart development?
Days 20-50 after fertilisation
How does oxygenated blood form the mother enter foetal circulation?
Via the umbilical vein through the ductus venosus
How does blood get to the left side of the heart in the foetus?
Via Foramen Ovale
Left Atrium – Left Ventricle – Aorta (Ao)
How does blood get to the aorta from the right side of the heart in the foetus?
Right Ventricle – Pulmonary Artery (PA) - Patent Ductus Arteriosus (PDA) – Aorta
(bypasses the lungs)
What are normal O2 sats in the foetus?
60-70%
What does the ductus arteriorus do?
Protects lungs against circulatory overload
Allows the right ventricle to strengthen
Carries low oxygen saturated blood
What does the ductus venous do?
Foetal blood vessel connecting the umbilical vein to the IVC
Blood flow regulated via sphincter
Carries mostly oxygenated blood
What is the normal heart rate for a newborn?
120-160 bpm
Tachycardia - >160 bpm
Bardycardia - < 100 bpm
What is the normal resp rate in the newborn?
30-60 /min
Periodical
What is the normal BP in the newborn?
1 hr - 70/44
1 day - 70±9/42±12
3 days - 77±12/49±10
How do babies thermoregulate?
Maternal thermoregulation in the womb
Newborn babies lack shivering thermogenesis thus need a metabolic production of the heat
Brown fat well innervated by sympathetic neurones so cold stress leads to lipolysis and heat production
BABIES DO NOT SHIVER
What does cold stress lead to?
lipolysis and heat production of brown fat
In what 4 ways do babies lose heat?
Radiation:
Heat dissipated to colder objects.
Convection:
Heat loss by moving air.
Evaporation:
We are born in water.
Conduction:
Heat loss to surface on which baby lies.
How might you assess newborn breathing non-invasively?
Blood gas determination - PaCO2 5-6 kPa, PaO2 8-12 kPa
Trans-cutaneous pCO2/O2 measurement
How might you assess newborn breathing invasively?
Capnography Tidal volume 4-6 ml/kg Minute ventilation: Tidal Volume ml/kg x respiratory rate Flow-volume loop.
When does physiological jaundice appear?
Day 2-3
When does physiological jaundice disappear?
Within 7-10 DOL in term infants and up to 21 DOL in premature infants
How does blue light prevent kernicterus?
Blue light converts bilirubin to water soluble form and increases oxidation of bilirubin.
Why is it normal for a baby to have a weight loss of 10%?
Shift of interstitial fluid to intravascular
Diuresis
For how long is it normal for a baby not to pass urine?
First 24 hours
How well do full-term babies manage fluid/electrolyte balance?
Well
Why do premature infants not manage fluids so well?
Less fat in body composition
Increased loss through kidney:
- Slower GFR
- Reduced Na reabsorption
- Decreased ability to concentrate or dilute urine
Increased Insensible Water Loss (IWL)
- Via immature skin and breathing
- Physiological IWL is 20-40 ml/kg/day but could be up to 82 ml/kg/day in 750-1000 g
How do infant weight losses compare depending on term?
Physiological IWL is 20-40 ml/kg/day but could be up to 82 ml/kg/day in 750-1000 g
What is normal temperature in the newborn?
Same as adult
What are the ranges for blood gases in the newborn?
PaCO2 5-6 kPa, PaO2 8-12
How does RBC production compare on DOL 7 with that in the uterus?
About 1/10 of the production
How may a baby’s haemoglobin levels change over time?
Born with - Hb 15-20 g/l
Week 10 - Hb 11.4 g/l
Increase production of Erythropoetin
Week 20 - Hb 12.0 g/l
What are the causes of anaemia of prematurity?
Reduced erythropoesis
Blood letting – most important cause! (iatrogenic)
