Neonatology

Question 1

What is the main mechanism of perinatal asphyxia? (1)

Answer 1

Gas exchange, (placental or pulmonary) is compromised or ceases altogether => cardiorespiratory depression => hypoxia, hypercarbia and metabolic acidosis. Reduced cardiac output = reduced tissue perfusion => hypoxic-ischaemic encephalopathy. (HIE)

Question 2

Give 3 causes of hypoxic-ischaemic encephalopathy. (3)

Answer 2

Placental - excessive or prolonged uterine contractions, placental abruption or ruptured uterus.

Umbilical flow - cord compression from shoulder dystocia or cord prolapse

Inadequate maternal placental perfusion, maternal hypotension or hypertension

Failure of cardiorespiratory adaptation at birth

Question 3

How are the clinical manifestations of hypoxic-ischaemic encephalopathy (HIE) graded? (3)

Answer 3

Clinical manifestations begin immediately up to 48 hours.

Mild - irritable, staring eyes, hyperventilation

Moderate - abnormal tone and movement, can’t feed, may have seizures.

Severe - no normal spontaneous movements or response to pain, prolonged seizures, alternation between hypo and hypertonia; multi organ failure is present.

Question 4

Why might clinical manifestations of hypoxic-ischaemic encephalopathy (HIE) not present until 48 hours later? (1)

How can secondary neuronal damage be prevented? (1)

Answer 4

Immediate symptoms are caused by primary neuronal death, however delayed symptoms are caused by reperfusion injury leading to secondary neuronal death.

Mild hypothermia (33-34’C) can offer neuroprotection.

Question 5

What is caput succedaneum? (1)

What is the prognosis? (1)

Answer 5

Birth injury => bruising and oedema of the presenting part of the foetus extending beyond the margins of the skull bones.

Resolves within a few days.

Question 6

What is a cephalhaemotoma? (1)

What is the prognosis? (1)

Answer 6

Soft tossue birth injury - haemoatoma from bleeding below the periosteum, confined within the margins of the skull sutures. Usually involves the parietal bone.

Resolves over several weeks.

Question 7

What are the two commonest causes of brachial plexus injuries in a newborn? (2)

Answer 7

Breech delivery and shoulder dystocia

Question 8

Describe Erb’s Palsy. (2)

What part of the brachial plexus is affected? (1)

What other palsy may accompany Erb’s palsy? (1)

What is the prognosis? (1)

Answer 8

Affected arm is straight and limp, with pronated hand and flexed fingers.

Roots C5 and C6.

Phrenic palsy - elevated diaphragm.

Most resolve completely by 2 years, but shoul dbe referred if not resolved by 2-3 months.

Question 9

Why might a facial nerve palsy occur in a neonate? (1)

How might it manifest clinically? (2)

What is the prognosis? (1)

Answer 9

Compression of facial nerve against mother’s ischial spine.

It is unilateral and there is facial weakness on crying but eye remains open.

Transient but may require eye drops to avoid dryness.

Question 10

What is a term infant? (1)

Define pre-term. (1)

Define very pre-term. (1)

Define extrememly preterm. (1)

Answer 10

Infant born alive at gestational age 37 weeks+

Pre-term= 32-37/40

Very pre-term= 28-32/40

Extremely pre-term= <28/40

Question 11

What fractures are most commonly seen during birth. (3)

Answer 11

Clavicle - shoulder dystocia

Mid shaft femur (breech) or humerus (shoulder dystocia)

Question 12

What is hyaline membrane disease better known as? (1)

Why does it occur? (2)

When is it most commonly seen? (1)

How can it be prevented? (1)

Answer 12

Respiratory distress syndrome.

Deficiency of surfactant. Surfactant is secreted by type II pneumocytes of the alveolar epithelium and its role is reduce surface tension. In RDS, lack of surfactant causes alveolar collapse and inadequate gas exchange.

Very Pre-term - Vast majority before 28 weeks gestation, 50% born 28-32 weeks gestation - boys more severely affected than girls.

Antenatal glucocorticoids if preterm delivery anticipated.

Question 13

A 26/40 girl is delivered by emergency C/S for foetal distress. At birth she required intubation in the delivery room due to cyanosis, RR > 60, retractions and grunting expirations.

What is the diagnosis? (1)

What changes would you expect on chest X-ray? (1)

What is the cause of the grunting expirations? (1)

How long does RDS present after birth? (1)

What is the management? (2)

Answer 13

Respiratory distress syndrome.

Diffuse ground glass appearance, heart border is indistinct or obscured.

Grunting is in order to try to create positive airway pressure during expiration and maintain functional residual capacity.

Immediately after birth or up to 4 hours after birth.

Surfactant therapy placed via tracheal tube. Raised ambient oxygen possibly with CPAP or artificial ventilation via tracheal tube adjusted to infants oxygenation.

Question 14

Why are infants with RDS ventilated with the lowest pressures that provide adequate chest movement and satisfactory blood gases? (1)

Answer 14

Prevention of pneumothoraces.

Question 15

How does RDS cause pneumothorax? (2)

Answer 15

Overdistended alveoli rupture and allow air into interstitium (pulmonary interstitial emphysema), air can then track into the pleural cavity resulting in pneumothorax.

Up to 10%

Question 16

Why are preterm infants particularly susceptible to hypothermia?

Answer 16

Large surface area:mass ratio = greater heat loss than heat generation

Skin is thin and heat permeable - transepidermal water loss

Little subcutaneous fat for insulation

Cannot conserve heat by curling up or generate it by shivering

Question 17

Why is hypothermia so bad is preterm infants? (2)

Answer 17

Hypothermia = increased energy consumption => hypoxia and hypoglycaemia => failure to gain weight and increased mortality.

Question 18

If an infant is symptomatic with a patent ductus arteriosus, how can it be closed? (2)

Answer 18

Pharmacologic - prostaglandin synthetase inhibitor eg indometacin or ibuprofen

Sugical ligation if pharmacologic methods fail

Question 19

What signs may be present with a patent ductus arteriosus? (2)

Answer 19

May be asymptomatic or..

may have apnoea, bradycardia, SOB or increased O2 requirement.

Bounding pulse from increased pulse pressure, prominent apex beat, systolic murmur

Signs of heart failure

Question 20

Why do preterm babies have a high nutritional requirement? (1)

Answer 20

Rapid growth - double birthweight in 6 weeks and treble birthweight in 12 weeks.

Question 21

Why are foetuses at risk from any diseases that the mother may acquire during pregnancy? (1)

Answer 21

Only IgG cross placenta and mainly in 3rd trimester.

IgM and IgA are the antibodies made during an acute infection and as they are unable to cross the palcenta the child is therefore unprotected.

Question 22

What is the imaging investigation of choice to look for haemorrhages in the brain of a very low birthweight baby? (1)

Answer 22

Cranial ultrasound.

Question 23

NEC is associated with bacterial invasion of ischaemic bowel wall.

Name 3 risk factors for the development of necrotising enterocolitis. (3)

Name 1 protective factor. (1)

Name 3 signs of NEC. (3)

What changes might you see on x-ray? (3)

What is the management? (3)

Answer 23

Preterm infant, first few weeks of life, fed cow’s milk formula.

Breast milk alone is protective.

Stops tolerating feeds, regurgitating milk which may be bile-stained, distended abdomen, blood in stools.

Distended loops of bowel, thickening of bowel wall with intramural gas, may lead to bowel perforation.

NBM - parenteral feeding, broad-specturm antibiotics for aerobic and anaerobic cover, possibly artificial ventilation and circulatory support.

Question 24

What is the pathophysiology of retinopathy or prematurity? (2)

Answer 24

Developing blood vessels at the junctino of the vascular and non-vascularised retina. There is vascular proliferation which may progress to retinal detachment, fibrosis and blindness.

Laser therapy, eyes screened weekly if <32/40 or <1.5kg

Question 25

What is bronchopulmonary dysplasia? (1)

What is the imaging of choice, and what would you expect to see. (2)

Answer 25

Infants who still require oxygen at a gestational age of 36 weeks are described as having bronchopulmonary dysplasia or chronic lung disease. The damage come from pressure and volume related trauma from artificial ventilation, infection and oxygen toxicity.

Xray- widespread opacification sometimes with cystic changes.

Question 26

Why do preterm babies require supplementary iron? (1)

Answer 26

Most iron is transferred in third trimester - so preterm babies iron stores are low. Therefore at risk of anaemia of the newborn.

Question 27

What is the commonest cause of respiratory distress in term infants? (1)

What is the pathophysiology and why is it more commonly seen after c/s deliveries? (2)

How is it diagnosed? (1)

Answer 27

Transient tachypnoea of the newborn

Caused by delay in the reabsorption of lung fluid and is more common after c/s because of the lack of thoracic compression that occurs during labour and NVD.

It is a diagnosid of exclusion.

Question 28

What is the pathophysiology of meconium aspiration? (3)

What signs may be seen on cxr? (3)

Answer 28

Meconium is passed in utero due to foetal hypoxia - at birth asphyxiated infants may start gasping and inhale the thick meconium resulting in both a mechanical obstruction as well as a chemical pneumonitis.

Lungs overinflated, accommpanied by patches of collapse and consolidation. High incidence of air leak leads to pneumothorax and pneumomediastinum.