Neonates: HIE, Neonatal Respiratory Distress Syndrome, Meconium Aspiration Syndrome

Question 1

What is hypoxic ischaemic encephalopathy (HIE)?

Answer 1

Occurs in neonates as a result of severe or prolonged hypoxia during birth.

Hypoxia: a lack of oxygen.
Ischaemia: a restriction in blood flow to the brain.
Encephalopathy: malfunctioning of the brain.

Question 2

What are some causes of HIE?

Answer 2

Anything that leads to asphyxia (deprivation of oxygen) to the brain:

1) Maternal shock

2) Intrapartum haemorrhage

3) Prolapsed cord: causing compression of the cord during birth

4) Nuchal cord: where the cord is wrapped around the neck of the baby

Question 3

What staging system is used in HIE?

Answer 3

Sarnat staging

Question 4

What are the 3 stages of Sarnat Staging for HIE?

Answer 4

1) Mild

2) Moderate

3) Severe

Question 5

Features of ‘mild’ HIE?

Answer 5

1) Poor feeding, generally irritability and hyper-alert

2) Resolves within 24 hours

3) Normal prognosis

Question 6

Features of ‘moderate’ HIE?

Answer 6

• Poor feeding, lethargic, hypotonic and seizures
• Can take weeks to resolve
• Up to 40% develop cerebral palsy

Question 7

Features of ‘severe’ HIE?

Answer 7

• Reduced consciousness, apnoeas, flaccid and reduced or absent reflexes
• Up to 50% mortality
• Up to 90% develop cerebral palsy

Question 8

What long term complication is HIE associated with?

Answer 8

Cerebral palsy

Question 9

Management of HIE?

Answer 9

1) Specialised care in neonatal unit

2) Therapeutic hypothermia

3) Following up by a paediatrician and the MDT to assess their development and support any lasting disability

Question 10

What is the role of therapeutic hypothermia in HIE?

Answer 10

Babies near or at term considered to have HIE can benefit from therapeutic hypothermia. This involves actively cooling the core temperature of the baby according to a strict protocol.

The intention is to reduce the inflammation and neurone loss after the acute hypoxic injury. It reduces the risk of cerebral palsy, developmental delay, learning disability, blindness and death.

Question 11

What happens in therapeutic hypothermia in suspected HIE?

Answer 11

The baby is transferred to neonatal ICU and actively cooled using cooling blankets and a cooling hat.

The temperature is carefully monitored with a target of between 33 and 34°C, measured using a rectal probe.

This is continued for 72 hours, after which the baby is gradually warmed to a normal temperature over 6 hours.

Question 12

When should HIE be suspected?

Answer 12

1) events that could lead to hypoxia during the perinatal or intrapartum period

2) acidosis (pH < 7) on the umbilical artery blood gas

3) poor Apgar scores

4) features of mild, moderate or severe HIE

5) evidence of multi organ failure.

Question 13

Which neonates does respiratory distress syndrome (RDS) affect?

Answer 13

Premature neonates, born before the lungs start producing adequate surfactant.

Commonly occurs <32 weeks gestation.

Question 14

CXR findings in neonate RDS?

Answer 14

‘Ground glass’ appearance.

Question 15

Pathophysiology behind RDS in premature neonates?

Answer 15

1) Inadequate surfactant leads to high surface tension within alveoli.

2) This leads to atelectasis (lung collapse), as it is more difficult for the alveoli and the lungs to expand.

3) This leads to inadequate gaseous exchange, resulting in hypoxia, hypercapnia (high CO2) and respiratory distress.

Question 16

What is given to mothers with suspected or confirmed preterm labour to increase the production of surfactant?

Answer 16

Antenatal steroids e.g. dexamethasone

Question 17

What support may premature neonates need to reduce RDS?

Answer 17

1) Intubation and ventilation to fully assist breathing if the respiratory distress is severe

2) Endotracheal surfactant, which is artificial surfactant delivered into the lungs via an endotracheal tube

3) CPAP via a nasal mask to help keep the lungs inflated whilst breathing

4) Supplementary oxygen to maintain oxygen saturations between 91 and 95% in preterm neonates

Question 18

Short term complications of RDS in premature neonates?

Answer 18

• Pneumothorax
• Infection
• Apnoea
• Intraventricular haemorrhage
• Pulmonary haemorrhage
• Necrotising enterocolitis

Question 19

Long term complications of RDS in premature neonates?

Answer 19

1) Chronic lung disease of prematurity

2) Retinopathy of prematurity occurs more often and more severely in neonates with RDS

3) Neurological, hearing and visual impairment

Question 20

Clinical features of neonatal RDS?

Answer 20

The symptoms of NRDS are often noticeable immediately after birth and get worse over the following few days.

1) cyanosis
2) increased work of breathing
3) grunting sound

Question 21

Investigations in neonatal RDS?

Answer 21

1) ABG

2) pulse ox

3) CXR

Question 22

What is meconium?

Answer 22

Meconium is the first material to pass through the foetal intestinal tract. It is composed of cells from intestine, skin, hair, vernix and amniotic fluid.

It is a dark green, sticky and lumpy faecal material.

Question 23

What is meconium aspiration syndrome (MAS)?

Answer 23

The term used to describe a spectrum of disorders, marked by various degrees of respiratory distress in the new born infant.

This follows the aspiration of meconium stained amniotic fluid, which can happen either antenatally or during birth.

Question 24

What happens in MAS?

Answer 24

Meconium is usually released from the bowels after birth.

In some pregnancies, the baby can pass meconium in utero, leading to meconium stained amniotic fluid (MSAF).

Of these, 5-12% of babies can aspirate this MSAF and develop MAS.

When this happens, MAS can cause the new born to develop respiratory distress which may be life threatening due to inflammatory response in the lungs.

It also inhibits the effect of surfactant in the lungs.

Question 25

What are some risk factors for MAS?

Answer 25

1) Post term babies (gestational Age > 42 weeks)

2) Babies who had thick meconium at birth

3) Babies who suffered birth asphyxia

4) Babies that are small for gestational age

5) Materal: HTN, pre-eclampsia, chorioamnionitis, smoking or substance abuse.

Question 26

Clinical features of MAS?

Answer 26

1) Meconium-stained liquor

2) Respiratory distress at or shortly following birth: tachypnoea, tachycardia, cyanosis, grunting, nasal flaring

3) Increased oxygen requirements (mechanical ventilation may be required for severe cases)

4) Hypotension

Question 27

What common features are seen with MAS-related respiratory distress of the newborn?

Answer 27

1) Partial or Total Airway Obstruction: due to thick and sticky consistency of meconium

2) Foetal Hypoxia

3) Pulmonary Inflammation

4) Infection

5) Surfactant Inactivation

6) Persistent Pulmonary Hypertension (PPHN): results from remodelling of the pulmonary vascular bed in response to hypoxia, vasoactive mediators in the meconium and V/Q mis-match.

Question 28

What is effect of meconium on the respiratory system?

Answer 28

1) Respiratory distress:
- damaging effect on surfactant and its metabolisn –> increased surface tension, reduced lung volume, reduced compliance and reduced oxygenation.

2) Pneumonitis

3) Bacterial pneumonia (E. coli in particular)

4) Pneumothorax:
- if thick, can cause airway obstruction in distal small airways
- meconium plugging and distal gas trapping can lead to distention of distal lung and pneumothorax

Question 29

Bedside investigations in MAS?

Answer 29

1) Pre- and post-ductal saturations: to assess respiratory involvement and detect congenital cardiac lesions

2) ABG or VBG: to assess the degree of respiratory compromise and assist in decisions regarding respiratory support and systemic involvement

Question 30

Lab investigations in MAS?

Answer 30

1) FBC: to look for raised white cell count suggestive of an infective process

2) CRP: to look for an infective process

3) Blood cultures: to look for bacteraemia suggestive of sepsis and/or pneumonia

Question 31

1st line imaging in MAS?

Answer 31

CXR

Question 32

CXR findings in MAS?

Answer 32

1) hyperinflated lungs due to distal air trapping

2) asymmetrical patchy pulmonary opacities

3) may show pneumothorax or pneumomediastinum due to raised alveolar tension

4) pleural effusions

Question 33

Give 3 differentials for MAS

Answer 33

1) Transient tachypnoea of the newborn

2) Surfactant deficiency

3) Persistent pulmonary hypertension

Question 34

What is transient tachypnoea of the newborn?

Answer 34

This is a tachypnoea present in the newborn infant, which usually resolves after 24hr without any intervention.

Neither hypoxia nor cyanosis are usually seen, but the child might need support on a neonatal unit if they are symptomatic.

Question 35

What intrapartum preventative measures may be taken to avoid meconium aspiration syndrome?

Answer 35

1) prevention of foetal hypoxia

2) prevention of postdates gestation

Question 36

For infants who are born through meconium-stained liquor, what preventative measures for MAS may be taken?

Answer 36

A vigorous infant –> requires no oropharyngeal suctioning despite the meconium-stained liquor as this does not reduce the risk of meconium aspiration syndrome.

A non-vigorous infant –> should not have routine endotracheal suction for meconiu BUT may require oropharyngeal suctioning if there is meconium obstructing the airway. The priority should be to rapidly initiate ventilation.

Question 37

What is the Apgar score?

Answer 37

Score used to assess the health of a newborn baby.

Question 38

When is the Apgar score assessed?

Answer 38

1 and 5 minutes of age.

If the score is low then it is again repeated at 10 minutes.

Question 39

What does the Apgar scores indicate?

Answer 39

0-3: very low (bad)

4-6: moderately low

7-10: baby in a good state

Question 40

What makes up the Apgar score?

Answer 40

1) Pulse:
- >100 = 2 points
- <100 = 1 point
- absent = 0 points

2) Respiratory effort:
- strong, crying = 2 points
- weak, irregular = 1 point
- nil = 0 points

3) Colour:
- pink = 2 points
- body pink, extremities blue = 1 point
- blue all over = 0 points

4) Muscle tone:
- active movement = 2 points
- limb flexion = 1 point
- flaccid = 0 points

5) Reflex irritability:
- cries on stimulation/sneezes, coughs = 2 points
- grimace = 1 point
- nil = 0 points

Question 41

What Apgras score indicates the need for additional monitoring after birth?

Answer 41

≤8

Question 42

Management of MAS?

Answer 42

1) supportive e.g. O2, ventilation

2) surfactant therapy

3) Abx - usually started whilst awaiting blood cultures result

Question 43

Complications of MAS?

Answer 43

Most infants with MAS have a good outcome and are discharged home.

Short-term complications include:
- ongoing oxygen requirements
- seizures
- necrotising enterocolitis
- can be fatal

Some studies have suggested an increased incidence of reactive airways disease in infants who had MAS.

Question 44

What is neonatal abstinence syndrome (NAS)?

Answer 44

Refers to the withdrawal symptoms that happens in neonates of mothers that used substances in pregnancy.

Question 45

What substances can cause neonatal abstinence syndrome (NAS)?

Answer 45

1) Opiates

2) Methadone

3) Benzodiazepines

4) Cocaine

5) Amphetamines

6) Nicotine or cannabis

7) Alcohol

8) SSRI antidepressants

Question 46

When does NAS occur with withdrawal from most opiates, diazepam, SSRIs and alcohol?

Answer 46

3-72 hours after birth

Question 47

When does NAS occur with withdrawal from methadone and other benzos?

Answer 47

Between 24 hours and 21 days

Question 48

Features of NAS?

Answer 48

CNS:

• Irritability
• Increased tone
• High pitched cry
• Not settling
• Tremors
• Seizures

Vasomotor and respiratory:

• Yawning
• Sweating
• Unstable temperature and pyrexia
• Tachypnoea

Metabolic and gastrointestinal:

• Poor feeding
• Regurgitation or vomiting
• Hypoglycaemia
• Loose stools with a sore nappy area

Question 49

General approach to management of NAS?

Answer 49

1) Mothers that are known to use substances should have an alert on their notes

2) Babies are kept in hospital with monitoring on a NAS chart for at least 3 days (48 hours for SSRI antidepressants)

3) Urine sample from neonates

4) Neonate should be supported in a quiet and dim environment with gentle handling and comforting.

Question 50

What is the medical treatment option for moderate to severe symptoms for opiate withdrawal?

Answer 50

Oral morphine sulphate

Question 51

What is the medical treatment option for moderate to severe symptoms for non-opiate withdrawal?

Answer 51

Oral phenobarbitone

Question 52

Does NAS from SSRI withdrawal require medical treatment?

Answer 52

Typically no

Question 53

What pregnancy risks does smoking cause?

Answer 53

1) Increased risk of miscarriage (increased risk of around 47%)

2) Increased risk of pre-term labour

3) Increased risk of stillbirth

4) IUGR

5) Increased risk of sudden unexpected death in infancy

Question 54

What pregnancy risks does alcohol cause?

Answer 54

Fetal alcohol syndrome (FAS):
- learning difficulties
- characteristic facies: smooth philtrum, thin vermilion, small palpebral fissures, epicanthic folds, microcephaly
- IUGR & postnatal restricted growth

Note - Binge drinking is a major risk factor for FAS

Question 55

Maternal risks of cocaine use during pregnancy?

Answer 55

1) HTN in pregnancy including pre-eclampsia

2) Placental abruption

Question 56

Foetal risks of cocaine use during pregnancy?

Answer 56

1) prematurity

2) neonatal abstinence syndrome