Neonates: HIE, Neonatal Respiratory Distress Syndrome, Meconium Aspiration Syndrome Flashcards
What is hypoxic ischaemic encephalopathy (HIE)?
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.
What are some causes of HIE?
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
What staging system is used in HIE?
Sarnat staging
What are the 3 stages of Sarnat Staging for HIE?
1) Mild
2) Moderate
3) Severe
Features of ‘mild’ HIE?
1) Poor feeding, generally irritability and hyper-alert
2) Resolves within 24 hours
3) Normal prognosis
Features of ‘moderate’ HIE?
- Poor feeding, lethargic, hypotonic and seizures
- Can take weeks to resolve
- Up to 40% develop cerebral palsy
Features of ‘severe’ HIE?
- Reduced consciousness, apnoeas, flaccid and reduced or absent reflexes
- Up to 50% mortality
- Up to 90% develop cerebral palsy
What long term complication is HIE associated with?
Cerebral palsy
Management of HIE?
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
What is the role of therapeutic hypothermia in HIE?
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.
What happens in therapeutic hypothermia in suspected HIE?
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.
When should HIE be suspected?
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.
Which neonates does respiratory distress syndrome (RDS) affect?
Premature neonates, born before the lungs start producing adequate surfactant.
Commonly occurs <32 weeks gestation.
CXR findings in neonate RDS?
‘Ground glass’ appearance.
Pathophysiology behind RDS in premature neonates?
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.
What is given to mothers with suspected or confirmed preterm labour to increase the production of surfactant?
Antenatal steroids e.g. dexamethasone
What support may premature neonates need to reduce RDS?
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
Short term complications of RDS in premature neonates?
- Pneumothorax
- Infection
- Apnoea
- Intraventricular haemorrhage
- Pulmonary haemorrhage
- Necrotising enterocolitis
Long term complications of RDS in premature neonates?
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
Clinical features of neonatal RDS?
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
Investigations in neonatal RDS?
1) ABG
2) pulse ox
3) CXR
What is meconium?
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.
What is meconium aspiration syndrome (MAS)?
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.
What happens in MAS?
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.
What are some risk factors for MAS?
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.
Clinical features of MAS?
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
What common features are seen with MAS-related respiratory distress of the newborn?
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.
What is effect of meconium on the respiratory system?
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
Bedside investigations in MAS?
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
Lab investigations in MAS?
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
1st line imaging in MAS?
CXR
CXR findings in MAS?
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
Give 3 differentials for MAS
1) Transient tachypnoea of the newborn
2) Surfactant deficiency
3) Persistent pulmonary hypertension
What is transient tachypnoea of the newborn?
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.
What intrapartum preventative measures may be taken to avoid meconium aspiration syndrome?
1) prevention of foetal hypoxia
2) prevention of postdates gestation
For infants who are born through meconium-stained liquor, what preventative measures for MAS may be taken?
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.
What is the Apgar score?
Score used to assess the health of a newborn baby.
When is the Apgar score assessed?
1 and 5 minutes of age.
If the score is low then it is again repeated at 10 minutes.
What does the Apgar scores indicate?
0-3: very low (bad)
4-6: moderately low
7-10: baby in a good state
What makes up the Apgar score?
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
What Apgras score indicates the need for additional monitoring after birth?
≤8
Management of MAS?
1) supportive e.g. O2, ventilation
2) surfactant therapy
3) Abx - usually started whilst awaiting blood cultures result
Complications of MAS?
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.
What is neonatal abstinence syndrome (NAS)?
Refers to the withdrawal symptoms that happens in neonates of mothers that used substances in pregnancy.
What substances can cause neonatal abstinence syndrome (NAS)?
1) Opiates
2) Methadone
3) Benzodiazepines
4) Cocaine
5) Amphetamines
6) Nicotine or cannabis
7) Alcohol
8) SSRI antidepressants
When does NAS occur with withdrawal from most opiates, diazepam, SSRIs and alcohol?
3-72 hours after birth
When does NAS occur with withdrawal from methadone and other benzos?
Between 24 hours and 21 days
Features of NAS?
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
General approach to management of NAS?
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.
What is the medical treatment option for moderate to severe symptoms for opiate withdrawal?
Oral morphine sulphate
What is the medical treatment option for moderate to severe symptoms for non-opiate withdrawal?
Oral phenobarbitone
Does NAS from SSRI withdrawal require medical treatment?
Typically no
What pregnancy risks does smoking cause?
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
What pregnancy risks does alcohol cause?
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
Maternal risks of cocaine use during pregnancy?
1) HTN in pregnancy including pre-eclampsia
2) Placental abruption
Foetal risks of cocaine use during pregnancy?
1) prematurity
2) neonatal abstinence syndrome
