Physiology of Neonates Flashcards
What carries oxygenated blood to the baby
What carried deoxygenated blood
Umbilical vein
Carries O2 blood from placenta to foetus
Umbilical artery x2 - from bifurcation of aorta - placenta
What is the ductus venous and what type of blood
Foetal blood vessel connecting umbilical vein from placenta to IVC of baby
Mostly oxygenated
Liver gets most oxygenated blood as first organ where umbilical vein goes
What is the foramen ovale
Hole connecting RA-LA
Bypass immature lungs which have a very high pressure
What is the ductus arteriosus
Allows blood flow from Pulmonary artery to aorta without travelling through foetal inadequate lungs
If it doesn’t close blood flows from aorta -> Pa
What does ductus arteriosus allow
RV to strengthen
Protect lungs from circulatory overload
What does ductus arteriosus carry
Low oxygen saturated blood
What is the saturation in a foetus
60-70%
When does CVS start to develop
End of third week
Heart beats at 4th week
What happens at first breath
Move fluids out of lungs and arteries / alveoli in lungs open
Decreases pulmonary vascular resistance
LA pressure > RA pressure which squishes atrial septum closing foramen oval
Foramen ovale closes - hard top open after 14 days
PDA stays open 1-2 days
Others all become ligaments
What are vital signs of newborn
BP 70/40ish RR - 30-60 HR- 120-160 Tachy >160 Brady <100
How do new born babies thermoregulate
Lack shivering thermogenesis
Rely on metabolic heat
Brown fat innervated by sympathetic
If premature lack brown fat
What are the 4 ways to lose heat
Radiation - to colder
Convection - moving air
Evaporation - to water
Conduction - to surface you touch
How do you assess newborn breathing non-invasively
Clinical - RR
Blood gas determination - take capillary blood + analyser
Trans-cutaneous PCO2,O2
What should the PaCo2 and PaO2 be in a newborn
PaCO2 - 5-6
PaO2 - 8-12
How do you assess breathing invasively
Capnography - monitors PaCO2 in intubation
What is TV average and minute volume
TV = 4-6ml / kg
Minute ventilaiton = TV x RR
Physiological jaundice
Day 2-3 and disappears in 7-10 days or three weeks in prem
Breast feed increases duration
Fluid balance in newborn term
Should be able to maintain fluid and electrolyte balance
U+E may be of first 24 hours as mother may have had IV fluids
Normal not to pass urine for 24 hours
Weight loss up to 10% is normal
Fluid balance in premature ?
Less fat
Increased loss through kidney
Increased insensible water loss
Why is there increased loss through kidney in premature
Slower GFR
Reduced Na reabsorption
Decreased ability to concentrate or dilute urine
Physiological anaemia
Reduced RBC production when born then increases
What is physiological of anaemia in prematurity
Reduced erythropoiesis when first born
Can’t keep up with rapid growth
Blood letting / tests remove blood volume
Infections
How do you treat
Give iron at 28 days if premature
What should happen to Hb when born
Should go up to provide O2
What do you do if low
Look at reticulocyte count to see if haemolytic
Why are bloods not accurate 1st 24 hours
Affected by mother e.g. if had IV fluid
Repeat
What happens if ductus arteriosus doesn’t close
Blood goes from aorta to lungs as higher pressure
When is surfactant produced
24-34 weeks gestation
Role of surfactant
Reduces force needed to expand the alveoli which reduces lung compliance
Why is hypoxia in baby common
Normal labour and birth cause hypoxia as contractions stop gas exchange with placenta
What does extended hypoxia lead too
Anaerobic respiration Bradycardia Reduced consciousness Drop in RR Eventually HIE
Other issues in neonatal resus
Large S/A to weight = cold easily
Born wet so lose heat
May have meconium in airway
What do you do if baby comes out not crying
Dry baby and stimulate
Keep warm under heat lamp or plastic bag if <28 weeks
Stimulate
Calculate APGAR - tone, RR, HR, colour, activity
Given a score for each 0-2
When is APGAR carried out
1,5 and 10 minutes
If not breathing what do you do or HR low
5 inflation breaths
- First breath to open up lungs so want large pressure
- Put pressure on mask
Aim is to sustain pressure to get fluid out
If this doesn’t work what do you do
Continuous pressure
What do you do if not improving or HR <60
CPR Ratio 3:1 with ventilation breaths IV access and drugs Intubation May benefit from hypothermia to prevent HIE
How often do you assess
30 seconds
What does APGAR look at
Appearance 0 =pale / blue 1 = pink with blue Pulse 0 =absent 1 = <100 Grimmace / activity - response to stimulation 0 = floppy 1 = minimal Tone 0 = absent 1 = flexed Respiration 0 = absent 1 = irregular
Given a score 0-2
Delayed cord clamping ?
If uncompromised wait 1 minute
Allows blood from placenta to enter baby
Reduce IVH, NEC and improve BP, iron and Hb
What are other causes of anaemia
Prematurity
Haemolysis
Blood loss
Twin-twin transfusion
What causes haemolytic
ABO or Rhesus
G6PD
Heriditary spherocytosis
What do you do if low blood sugar after birth
Encourage feeding Observe Trnasient hypo = common If DM mother start hypoglycaemic protocol - Dextrogel - IV dextrose - IV fluid
