Normal newborn

Question 1

CV changes at birth

Answer 1

• high pulmonary vascular resistance
• most blood on R side heart bypasses lung (through DA) and foramen ovale
• pulmonary expansion associated with
  
  • rise in oxygen tension
  • falling of pulmonary vasular resistance
  • increase in pulmonary blood flow
• filling of left atrium associated with
  
  • rise in left atrial pressue
  • closure of foramen ovale
• flow of oxygenated blood through DA associated with
  
  • ductal closure

Question 2

Respiratory changes at birth

Answer 2

• lungs filled with amniotic fluid
• pulmonary vasculature constricted therefore HIGH PULMONARY VASCULAR RESISTANCE
• shortly before and during labour, lung liquid reduced
• during delivery chest squeezed, some fluid drained
• stimuli: thermal, tactile, hormonal (catecholamines!) inititate breathing
• average time to first breath is 6s after delivery
• mean time to establish regular breathing is 30s after delivery
• lung explansion established with intrathoracic negative pressure
• majority of lung fluid absorbed into lymphatics and pulmonary circulation

Question 3

Time frames for:

• passing urine
• opening bowels
• regaining birth weight

Answer 3

• Urination should occur within 48 hrs after birth
  
  • renal agenesis
  • obstructive uropathy
• Meconium usually passed within 12 hours of life (worry at 24 hr)
  
  • Hirschprungs
  • Imperforate anus
• Weight loss in first week of life = 8-10%
  
  • meconium
  • urine
  • loss of extracellular fluid
• Weight is regained by day 10-14

Question 4

Importance of Vit. K prophylaxis

Answer 4

• Vit. K given by IM injection- parents may request oral instead (3 doses required over first four weeks of life to give adequate liver storage)
• all infants immediately after birth
• prevention of haemoplytic disease of the newborn
• breast milk is poor source of Vit. K
• mothers taking anti-epileptics (impair synthesis of Vit. K clotting factors)
  
  • prophylaxis PO at 36 weeks
  • baby IM
• infants with liver disease
  *

Question 5

Outline important screening methods during infancy

• newborn examination
• hearing screening
• Gutherie card
• antenatal screening

Answer 5

• Gutherie test
  
  • ​heel prick sample of blood
  • when feeding established (day 5-9)
  • phenylketonuria
  • hypothyroidism
  • cystic fibrosis- trypsin levels
  • haemoglobulinopathies (sickle cell and thalassaemia)
  • MCAD (medium chain acyl-CoA dehydrogenase) deficiency- rare inborn error of mitochondrial FA metabolism causing acute illness and hypoglycaemia following fasting
• Hearing
  
  • ​Evoked otoacoustic emission testing
  • automated auditory brainstem response audiometry
    
    • computer analysis of EEG waveform in response to clicks
  • referral to paediatric audiologist if abnormal