Foetal Physiology and Transition

Question 1

What are some changes that occur after birth?

Answer 1

• umbilical vessels constrict when cord cut
• decreased blood comes to the right heart - foramen ovale closure.
• decreased vascular resistance of pulmonary circulation. baby takes a breath dilates vessels.
  
  • fluid exists lungs - negative pressure draws fluid into tissues.

Question 2

Oxygen transport mechanisms in the fetus?

Answer 2

• increased O2 affinity in fetal Hb. HbF = alpha gamma chains.
  
  • newborns can have beta-thalassemia.
• relatively hypoxic in-utereo environment - normal to be born blue (white is severe anaemia).
• oxygen dissociation curve pO2 50% sat.

Question 3

Explain some aspects of the fetal lung. What is wet lung? What is surfactant?

Answer 3

• foetal breathing - small
• liquid is produced in the lung - switched off by adrenaline, and less produced after birth. Cold c-section is associated with excess lung fluid.
  
  • removed by lymphatics,
  • pulmonary circulation
  • squeezed out during birth
• surfactant
  
  • lipoprotein complex
  • SPB - 4 tpes of surfactant protein A,B,C,D, genetic defect in B is a problem.
  • DPPC because it deceases surface tension - (collapsing pressure increases as bubble gets smaller unless you decrease surface tension).
  • RDS - hyaline membrane disease

Question 4

What might polyhydramnios indicate?

Answer 4

• amniotic fluid almost entirely urine at term.
• renal problems - increase urine productions
• gastrointestinal
  
  • impaired swallowing
    
    • oesophageal atresia
    • TOF with OA
    • neurological disorder

Question 5

What does oligo/anhydramnios indicate?

Answer 5

• kidney dysfunction - leads to no lung development and other complications
• Potter’s syndrome
  
  • renal function
  • llung function
  • fatal

Question 6

What is the Head’s paradoxical reflex?

Answer 6

• application of positive pressure stops breathing in adults (but opposite in infants - stimulates in infants)

Question 7

How do you assess a newborn within the first few minutes?

Answer 7

• Apgar Scores: (ABCD others)
  
  • Airway
  • Breathing - staph pneumonia (only if intubated)
  • Circulation
  • Drugs - Vitamin K
    
    • don’t produce it as kids, haemorrhagic disease of newborn.
    • Everymonth particularly not breastfed.
  • Cord - 15cm long cut off - plastic clamp - off after 48hrs. Dries out. Drop off after 4-5days, a wound that can get infected:
    
    • staph aureus (thrombophlebitis, septic arthritis) - antiseptic
    • pus/erythema - culture.
  • skin, temperature

Question 8

How do you thermoregulate in babies at birth?

Answer 8

tympanic membrane temperature in adults, but in babies rectum or mouth or oesophageal probe or axilla.

• in uterus
  
  • mother is 37 degrees. Fetus is hotter than the mother.
• after birth
  
  • temperature drops to 36 degrees. 36.8+ by a couple of hours.
  • wrap the baby up - microclimate. Too hot from heat stroke can die, too cold can die.

in bed you get colder overnight. heat loss = heat production.

• Not much conduction, convection
• evaporation (wet on exit) - water vapour pressure (cold air dry).
• Babies at birth like burn patients, group of babies without keratin (<30weeks).

Question 9

What do you do in the first few hours after a baby is born for assessment?

Answer 9

• Observation: baby look and listen - should be screaming at the end.
  
  • First hour is a great time to say hi - they are switched on.
• CNS
  
  • Conciousness,
  • responsiveness,
  • posture,
  • movements
• CVS
  
  • auscultate
  • palpate -
    
    • abdo,
    • pulses,
    • genitalia (hydrocele, vagina, hypospadius - chordea),
    • hips, (DDH - Ortolani’s, Barlow’s, female Fhx, stablise with widely abducted). - shallow acetabulum, unstable hip.
    • limbs,
    • spine,
    • palate,
    • fundi - cataracts (open eyes - when vertical).
    • fontanelles, (ant/post fontanelle)
    • primitive reflexes. - Moro’s reflex (last) drop head, shins against
• Measure
  
  • weight
  • length
  • head circumference
  • sex, gestation

Question 10

What sensations can a baby feel?

Answer 10

Sensation

• vision - see well but short sighted, need to be within half a meter. Blink to light. prefer red, curves, intermediate illumination.
• hearing - prefer female, heart rate rises
• taste - salt vs sweet,
• smell - of mum’s breast pads after few days
• pain

Question 11

How does breast feeding ‘on demand’ is go in the first couple of days?

Answer 11

• day 0 -2 - not enough get hungry
• day 3-5 - too much. sleepy, engorgement
• day 5 - just right, wind - colic

Measure degree of success:

• weight gain
• behaviour
• bowel action/urine output

Problems?

• can’t suck - preterm, CNS, RDS
• needs more SGA

Question 12

Talk through the implications of Jaundice in newborns

Answer 12

• they eat and sleep hopefully. CNS
• jaundice:
  
  • bilirubin from RBC
  • taken into liver (conjugated)
  • excrete in fecal matter or kidneys
• placenta in utero lets mum get rid of it
  
  • once delivered - in gut - unconjugated/reabsorbed
  • in babies higher - hyperbilirubinemic (N: 20mmol/L, baby 30).
  • phototherapy for first few days.
• too early:
  
  • haemolysis (isoimmunization)
• too high
  
  • haemolysis
  • underfeeding
  • bruising
  • sepsis
  • breast milk
• too long
  
  • conjugated
    
    • hepatitis
    • biliary atresia
  • unconjugated
    
    • breast milk
    • hypothyroidism
    • infection

Question 13

Metabolic screening in the first few weeks in babies?

Answer 13

• Guthrie Panel
  
  • screen for:
    
    • PKU - refer to children, low phenylalanine diet (brain development), babies - lofenalac (special milk, women’s is teratogenic)
    • hypothyroidism - 2x as common 1in 5000, screen for TSH and get TFT. Bone age. Cretinism.
    • CF - 1 in 2500 - serum trypsinogen, mutation, then sweat test. Die in early life from lung and pancreatic problems.
    • 1 in 1000,000 or more common

Question 14

What is a Mnemonic for the APGAR score?

Answer 14

SHIRT:

• skin colour
• heart rate <100 or >160
• irritability (response to stimulation)
• respirations
• tone