Neonatology ||| Flashcards
What is the pathophysiology of hypoxic-ischaemic encephalopathy (3)?
- Perinatal asphyxia occurs, as gas exchange (placental or pulmonary) are compromised or ceases, resulting in cardiorespiratory depression
- Hypoxia, hypercarbia (CO2 retention) and metabolic acidosis follow
- Compromised cardiac output diminishes tissue perfusion causing hypoxic-ischaemic injury to the brain and other organs
What are the 5 most common causes of HIE?
HIE usually follows a significant hypoxic event immediately before or during labour or delivery
- Failure of gas exchange across the placenta - excessive or prolonged uterine contractions, placental abruption, ruptured uterus
- Interruption of umbilical blood flow - cord compression including shoulder dystocia, cord prolapse
- Inadequate maternal placental perfusion, maternal hypotension or hypertension
- Compromised fetus - intrauterine growth restriction, anaemia
- Failure of cardiorespiratory adaptation at birth - failure to breathe
What are the 3 grades of the clinical manifestations of HIE?
Mild - infant is irritable, responds excessively to stimulation, may have staring of the eyes, hyperventilation, hypertonia and has impaired feeding
Moderate - marked abnormalities of movement, is hypotonic, cannot feed and may have seizures
Severe - No normal spontaneous movements or response to pain, tone in the limbs fluctuate between hypotonia and hypertonia, seizures are prolonged and often refractory to treatment, multi-organ failure is present
Under what principle does mild therapeutic hypothermia work?
Neuronal damage may be immediate from primary neuronal death or may be delayed from reperfusion injury causing secondary neuronal death from secondary energy failure. This delay offers the opportunity for neuroprotection with mild therapeutic hypothermia
What is the immediate management of HIE (5)?
- Respiratory support
- Treatment of clinical seizures with anticonvulsants
- Fluid restriction because of transient renal impairment
- Treatment of hypotension by volume and inotrope support
- Monitoring and treatment of hypoglycaemia and electrolyte imbalance, especially hypocalcaemia
How does therapeutic hypothermia work?
Infant wrapped in a cooling blanket to rectal temperature of 33 degrees for 72 hours, started within 6 hours of birth. Reduces brain damage
In what infants are therapeutic hypothermia used for?
Infants 36 weeks gestation and over with moderate or severe HIE
What are the long-term neurodevelopment risks of HIE (2)?
- Brain damage resulting in disability or death
2. Cerebral palsy
What is the pathophysiology of RDS?
- Deficiency of surfactant, which lowers surface tension
2. Leads to widespread alveolar collapse and inadequate gas exchange
What forms surfactant?
Type 2 pneumocytes of the alveolar epithelium
What is surfactant made of and what is its role?
Mixture of phospholipids and proteins
Lowers surface tension
Before what weeks gestation is RDS particularly common in?
Before 28 weeks gestation
What is the given to the mother if preterm delivery is anticipated to prevent RDS?
Glucocorticoids
What are 4 signs of RDS at delivery or within 4 hours of birth in babies?
- Tachypnoea over 60 breaths/min
- Laboured breathing with chest wall recession (especially sternal and subcostal indrawing) and nasal flaring
- Expiratory grunting to try to create positive airway pressure during expiration and maintain functional residual capacity
- Cyanosis if severe
What is the management of RDS after birth (3)?
- Raised ambient O2
- Surfactant therapy may be given by instilling surfactant directly into the lungs via a tracheal tube or catheter
- Additional respiratory support
- Non-invasive CPAP/high-flow nasal cannula (non-invasive preferred if possible)
- or invasively with mechanical ventilation
What 3 things are mechanical ventilation adjusted according to?
- Infants oxygenation
- Chest wall movements
- Blood gas analysis
What medical problems are preterm infants more likely to get (16)?
- Need for resus and stabilisation at birth
- Respiratory problems
- RDS
- pneumothorax
- apnoea and bradycardia - Hypotension
- Patent ductus arteriosus
- Temperature control
- Metabolic:
- hypoglycaemia
- hypocalcaemia
- electrolyte imbalance
- osteopenia of prematurity - Nutrition
- Infection
- Jaundice
- Intraventricular haemorrhage/periventricular leukomalacia
- Necrotising enterocolitis
- Retinopathy of prematurity
- Anaemia of prematurity
- Iatrogenic
- Bronchopulmonary dysplasia (BPD)
- Inguinal hernias
What weeks gestation are considered preterm?
23-37
What weeks gestation are considered term?
37-42
What is the clinical presentation of bradycardia and apnoea in preterm infants?
Bradycardia may occur when the infant stops breathing for over 20-30 seconds
or
When breathing but against a closed glottis
What is the most usual cause of apnoea and bradycardia in a preterm infant?
Immaturity of central respiratory control
What is the treatment of apnoea and bradycardia in a preterm infant (3)?
- Breathing usually starts again after gentle physical stimulation
- Respiratory stimulant caffeine
- CPAP or mechanical ventilation if apnoeic episodes are frequent
What are the consequences of hypothermia in a preterm infant (3)?
- Hypothermia causes increased energy consumption
- This can result in hypoxia and hypoglycaemia, failure to gain weight
- It is an independent risk factor for mortality soon after birth
What are 4 reasons that preterm infants are particularly vulnerable to hypothermia?
- Large surface area relative to their mass so there is greater heat loss than heat generation
- Skin is thin and heat permeable, so transepidermal water loss is important in the 1st week of life
- They have little subcutaneous fat for insulation
- Often nursed naked and cannot conserve heat by curling up or generate heat by shivering
What is the management/prevention of hypothermia in preterm infants (2)?
- Incubators
or - Overhead radiant heaters
Why is it important to provide adequate nutrition to preterm infants (3)?
- They have a high nutritional requirement because of their rapid growth
- Avoid poor bone mineralisation (osteopenia of prematurity) as a result of inadequate phosphate, calcium and vitamin D - treated with supplementation of milk
- Avoid low iron stores and iron deficiency as iron is transferred to fetus during the last trimester - treated with iron supplements
At how many weeks gestation are infants mature enough to suck and swallow milk?
35-36 weeks gestation
How are less mature infants fed?
Via an orogastric or nasogastric tube
What are preterm infants fed to ensure adequate nutrition (2)?
- Breast milk supplemented with phosphate and sometimes protein and calories and calcium
- Special infant formulas designed to meet the increased nutritional requirements of preterm infants (if formula feeding required)
What are some extremely preterm infants initially fed on if maternal breast milk is not available?
Donor breast milk
How are very immature or sick infants (typically <1kg birthweight) fed?
Paraenteral nutrition via a peripherally inserted central line (PIC or long line) or an umbilical venous catheter
Why is breast milk better than formula milk?
- Infants (2)
- Mother (1)
- Both (1)
Infant:
- Protection against infection
- Lowers risk of SIDS, diabetes, obesity etc in future
Mother:
1. Lowers risk of ovarian/breast cancer, CVD disease, obesity etc
Both:
1. Promotes bonding
Why are preterm infants at an increased risk of infection?
IgG is mostly transferred across the placenta in the last trimester and no IgA or M is transferred
What are 3 causes of infection in preterm infants?
- Infection in or around cervix which causes preterm labour and can cause infection shortly after birth
- Associated with indwelling catheters
- Associated with mechanical ventilation
When does the infection usually present in a preterm infant?
After several days of age
What are consequences of infection (3)?
- Death
- Bronchopulmonary dysplasia
- Brain injury -> disability
What is necrotising enterocolitis?
A serious illness occurring in preterm infants, where the bowel becomes inflamed and necrosed
At what age does NE usually present?
First few weeks of life
What are the 3 key risk factors for NE in preterm infants?
- Bowel of preterm infant is vulnerable to ischaemic injury
- Bowel of preterm infant is vulnerable to bacterial invasion
- More likely if fed cows milk than only breast milk
What are early (4) and late (3) signs of NE?
Early:
- Feed intolerance
- Vomiting -> may be bile stained
- Distended abdomen
- Fresh blood in stools
Later:
- Infant goes into shock
- Requires mechanical ventilation due to abdominal distension and pain
- Bowel perforation
What are the characteristic X-ray features of NE (2)?
- Distended loops of bowel
2. Thickening of bowel wall with intramural gas
How would you confirm a bowel perforation (2)?
- X-ray
2. Transillumination of the abdomen
What is the treatment of NE (6)?
- Stop oral feeding
- Give broad-spectrum Abx for aerobic and anaerobic
- Parenteral nutrition always needed
- Mechanical ventilation may be needed
- Circulatory support may be needed
- Surgery for bowel perforation
What is the long-term sequelae of NE (2)?
- Strictures
2. Malabsorption in extensive bowel resection
What % of very low birthweight infants develop a haemorrhage?
20%
What scan is best used to detect a brain haemorrhage in a preterm infant?
Cranial ultrasound scans
Where do the brain haemorrhages in the preterm infant usually occur?
The germinal matrix above the caudate nucleus, which contains a fragile network of blood vessels
- Small haemorrhages in the germinal matrix
- Larger haemorrhages extend into the ventricles
How many hours after birth does an intraventricular haemorrhage (IVH) occur in a preterm infant?
72 hours
What are 3 risk factors for IVH in preterm infants (3)?
- Perinatal asphyxia
- Severe RDS
- Pneumothorax
What is the most severe type of haemorrhage in preterm infants?
Unilateral haemorrhagic infarction involving the parenchyma of the brain, usually resulting in CP hemiplegia
What are the consequences of brain haemorrhages in preterm infants (2)?
- Unilateral haemorrhagic infarction involving parenchyma of brain -> hemiplegia
- A large IVH can impair drainage and reabsorption of CSF, causing build-up under pressure.This can resolve spontaneously or lead to hydrocephalus
What are the clinical features of hydrocephalus (3)?
- Cranial sutures separate
- Head circumference increases rapidly
- Anterior fontanelle becomes tense
How is hydrocephalus managed (2)?
- Symptomatic relief by removal of CSF by LP or ventricular tap
- Some may require a VP shunt
What is retinopathy of prematurity?
Vascular proliferation of the bv at the junction of the vascularised and non-vascularised retina
May progress to retinal detachment, fibrosis and blindness
What is a risk factor for retinopathy of prematurity?
Uncontrolled use of high concentrations of O2
What are the 2 treatment options for retinopathy of prematurity to reduce visual impairment?
- Laser therapy
2. Intravitreal anti-VEGF therapy
What is bronchopulmonary dysplasia?
Chronic lung disease - infants who still have an oxygen requirement at a post gestational age of 36 weeks
What is the pathophysiology of bronchopulmonary dysplasia?
Lung damage due to delay in lung maturation, also from pressure and volume trauma from artificial ventilation, oxygen toxicity and infection
What does the chest x-ray show for bronchopulmonary dysplasia?
Widespread areas of opacification, sometimes with cystic changes
What is the course of bronchopulmonary dysplasia (3)?
- Some infants need prolonged artificial ventilation
- Most are weaned onto CPAP or high-flow nasal cannula therapy followed by additional ambient oxygen
- Some with severe disease may die of itnercurrent infection or pulmonary hypertension
What are the neurodevelopmental complications of prematurity (4)?
- 5-10% of very low birthweight infants develop CP
- Most have learning difficulties
- A small proportion have hearing impairment
- A small proportion have visual impairment (1% blind in both eyes)
Why is hypoglycaemia common in the first 24 hours of life in a preterm infant?
They have poor glycogen stores
What are 6 symptoms of hypoglycaemia in a neonate?
- Jitteriness
- Irritablity
- Apnoea
- Lethargy
- Drowsiness
- Seizures
What is the suggested adequate level of blood glucose level for optimal neurodevelopmental outcome in a neonate?
Glucose levels above 2.6 mmol/l
What is the consequence of prolonged, symptomatic hypoglycaemia in a neonate?
Permanent neurological disability
How can hypoglycaemia be prevented in a neonate (2)?
- Early and frequent milk feeding
2. Blood glucose regularly monitored at the bedside
In an infant with 2 low glucose values (2.6mmol/l)in spite of adequate feeding, or one very low value (<1.6mmol/l), or becomes symptomatic, what is given?
Glucose by iv infusion aiming to maintain glucose level over 2.6 mmol/l via a central venous catheter
If there is difficulty or delay in starting an infusion, or a satisfactory response is not achieved in a neonate with hypoglycaemia, what can be given?
Glucagon
What area the 4 signs of respiratory distress in an infant?
- Tachypnoea (>60 breaths/min)
- Laboured breathing, with chest wall recession (particularly sternal and subcostal indrawing) and nasal flaring
- Expiratory grunting
- Cyanosis if severe
What is the general management of an infant with respiratory distress (4)?
- Admitted to neonatal unit for monitoring of heart and respiratory rates, oxygenation and circulation
- Chest x-ray will be needed to identify cause
- Additional ambient oxygen
- Respiratory support that may be non-invasive e.g. CPAP or high-flow cannula therapy
What are the causes of respiratory distress in an infant?
- Common (1)
- Less common (4)
- Rare (3)
- non-pulmonary (4)
Common
1. Transient tachypnoea of the newborn
Less common
- Meconium aspiration
- Pneumonia
- RDS
- Persistent pulmonary hypertension of the newborn
Rare
- Diaphragmatic hernia
- Tracheo-oesophageal fistula
- Pulmonary hypoplasia
Non-pulmonary
- Congenital heart diseaes
- Hypoxic-ischaemic/neonatal encephalopathy
- Severe anaemia
- Metabolic acidosis
What is the pathophysiology of transient tachypnoea of the newborn? What is its course?
Caused by a delay in resorption of lung liquid causing respiratory distress. It usually settles within 1st day of life but can take several days to resolve completely
What is a risk factor for transient tachypnoea of the newborn?
C-section
What would chest x-ray show for transient tachypnoea of the newborn?
Fluid in the horizontal fissure
How is transient tachypnoea of the newborn managed?
Additional ambient oxygen
How is transient tachypnoea of the newborn diagnosed?
Diagnosis of exclusion
What % of babies pass meconium before birth?
Why may it be passed?
8-20% - increasingly occurs with greater gestational age
May be in response to asphyxia
What are the consequences of meconium aspiration (3)?
- Meconium is a lung irritant and results in both mechanical obstruction and a chemical pneumonitis, as well as predisposing to infection
- May lead to persistent pulmonary hypertension of the newborn
- There is high incidence of air leak, which can lead to pneumothorax and pneumomediastinum
What does the chest x-ray show for meconium aspiration (3)?
- Lungs overinflated
- Areas of collapse
- Patches of colsolidation
What is the management of meconium aspiration?
Some may need mechanical ventilation
What is persistent pulmonary hypertension of the newborn?
A life-threatening condition usually associated with birth asphyxia, meconium aspiration, septicaemia or RDS
What is the pathophysiology of persistent pulmonary hypertension of the newborn?
High pulmonary vascular resistance means there is right-to-left shunting within the lungs and at atrial and ductal levels.
What signs are absent in persistent pulmonary hypertension of the newborn (2)?
- Signs of heart failure
2. Heart murmurs
What signs occur with persistent pulmonary hypertension of the newborn (2)?
- Cyanosis
2. Pulmonary oligaemia
What investigations are done for persistent pulmonary hypertension of the newborn and what do they show/what are they for (2)?
- Chest x-ray
- heart is of normal size
- pulmonary oligaemia - Urgent echocardiogram
- exclude congenital heart disease
- signs of pulmonary hypertension such as raised pulmonary pressures and tricuspid regurgitation
What is the management of persistent pulmonary hypertension of the newborn (3)?
- Mechanical ventilation
- Circulatory support
- Inhaled nitric oxide, a potent vasodilator is often beneficial
What is a diaphragmatic hernia?
When there is a hole in the diaphragm as it is not formed properly so bowel contents can enter the chest
How are diaphragmatic hernias diagnosed?
On antenatal ultrasound screening
How do diaphragmatic hernias present in the newborn period?
Failure to respond to resuscitation or respiratory distress
Where does the hole in the diaphragm usually occur in a diaphragmatic hernia?
Left side through the posterolateral foramen of the diaphragm
What are the signs of diaphragmatic hernias in a newborn (2)?
- Apex beat and heart sounds are displaced to the right side of the chest
- Poor air entry in left chest
How is the diagnosis of diaphragmatic hernia confirmed?
X-ray of chest and abdomen
What is the immediate and then management following stabilisation of a diaphragmatic hernia?
Immediate
- Once diagnosis is suspected, a large nasogastric tube is passed and suction applied to prevent distension of the intrathoracic bowel
Following stabilisation
- Diaphragmatic hernia is repaired surgically
What is the main problem of diaphragmatic hernias?
Pulmonary hypoplasia
- compression by the herniated viscera throughout pregnancy has prevented development of the lung in the fetus
- mortality is high in this case
What 3 things predispose to pneumonia?
- Prolonged rupture of the membranes
- Chorioamnionitis
- Low birthweight
How is congenital pneumonia managed?
Broad-spectrum abx started early until the results of the infection screen are available
What is early-onset infection?
Early-onset sepsis (<48 hours after birth)
How do bacteria and viruses infect the fetus in early-onset infection (2)?
- Bacteria have ascended from the birth canal and invaded the amniotic fluid, which is in direct contact with the fetal lungs. This leads to pneumonia and secondary bacteraemia/septicaemia
- Congenital viral infections and early-onset infection with Listeria monocytogenes, is acquired via the placenta following maternal infection
What is the presentation of neonatal septicaemia (9)?
- Respiratory distress
- Temperature instability
- Poor feeding
- Vomiting
- Apnoea and bradycardia
- Abdominal distension
- Jaundice
- Neutropenia
- Shock
Plus others
What are the investigations done for neonatal septicaemia (5)?
- Chest x-ray
- Septic screen
- FBC -> detect neutropenia
- Blood cultures
- CRP (but takes 12-24 hours to rise)
What is the treatment of neonatal septicaemia?
Abx started immediately without waiting for culture results
-iv abx given to cover group B strep, L. monocytogenes and other gram-positive organisms (usually benzylpenicillin or amoxicillin)
plus
-cover for gram-negative organisms (usually aminoglycoside such as gentamicin)
What is late-onset infection in a neonate?
> 48 hours after birth
What is the source of infection in late-onset infection in a neonate (3)?
Infant’s environment
- Indwelling central venous catheters for parenteral nutrition
- invasive procedures that break the protective barrier of the skin
- tracheal tubes