[88] Prematurity Flashcards
What common problems are associated with prematurity?
- Respiratory distress syndrome
- Necrotising enterocolitis
- Infection-
- Hypoglycaemia
- Temperature control
- Retinopathy of prematurity
- Intraventricular haemorrhage
What is the problem in RDS?
Deficiency of surfactant
What is the role of surfactant?
Lowers surface tension
What is surfactant made up of?
A mixture of phospholipids and proteins
What excretes surfactant?
Type 2 pneumocytes of the alveolar epithelium
What does surfactant deficiency lead to?
Widespread alveolar collapse and inadequate gas exchange
What happens to the incidence of RDS with increasing prematurity?
Increases
Who is RDS common in?
Infants born before 28 weeks
In what gender does RDS tend to be more severe in?
Boys
Can you get surfactant deficiency at term?
Rare, but can occur in diabetic mothers
How can RDS be avoided?
Glucocorticoids given to mother antenatally if preterm delviery is anticipated
How does maternal administration of glucocorticoids help in RDS?
Stimulates foetus to produce surfactant
What has been a major advancement in the treatment of RDS?
Development of surfactant therapy
What is surfactant therapy made from?
Extracts of calf or pig lung
How is surfactant therapy administered?
Instilled directly into lung via tracheal tube
How effective is surfactant therapy in RDS?
Shown to reduce mortality from RDS by 40% without increasing morbidity rate
When do symptoms of RDS begin?
At birth or within 4 hours of birth
What are the clinical signs of RDS?
- Tachypnoea >60breaths/min
- Laboured breathing with chest wall recession and nasal flaring
- Expiratory grunting
- Cyanosis if severe
What causes expiratory grunting in RDS?
It is to try and create positive airway pressure during expiration and maintain functional residual capacity
What does the CXR shown in RDS?
Diffuse granular or ‘ground glass’ appearance of lungs
Air bronchogram
Heart border becomes indistinct or completely obscured with severe disease
How is RDS treated?
Raised ambient oxygen, may need to be supplemented with CPAP or artificial ventilation via tracheal tube
What do the ventilation requirements need to be adjusted on the basis of in RDS?
According to infants oxygenation, chest wall movements, and blood gas analysis
What can be used to wean infants from added oxygen therapy in RDS?
High-flow humidified oxygen therapy via nasal cannulae
What is necrotising enterocolitis?
A serious illness associated with bacterial invasion of ischaemic bowel wall
Who does necrotising enterocolitis affect?
Mainly preterm infants in first few weeks of life
How does the feed of an infant affect their risk of necrotising enterocolitis?
Preterm infants fed on cow’s milk formula are more likely to develop this condition than if they are fed only on breast milk
How does necrotising enterocolitis present?
- Stops tolerating feeds
- Milk aspirated from stomach
- May be bile-stained vomiting
- Abdomen becomes distended
- Stool sometimes contains fresh blood
How might the presentation of necrotising enterocolitis progress?
Infant may rapidly become shocked and require artificial ventilation due to abdominal distention and pain
What are the characteristic x-ray features of necrotising enterocolitis?
- Distended loops of bowel
- Thickening of bowel wall with intramural gas
What might complicate necrotising enterocolitis?
Bowel perforation
How can bowel perforation in necrotising enterocolitis be detected?
- X-ray
- Transillumination of abdomen
What is the treatment for necrotising enterocolitis?
- Stop oral feeding
- Broad spectrum antibiotics
- Parenteral nutrition
- Artificial ventilation and circulatory support if required
What do the antibiotics given in necrotising enterocolitis need to cover?
Aerobic and anaerobic organisms
What treatment is required for bowel perforation caused by necrotising enterocolitis?
Surgery
What is the mortality of necrotising enterocolitis?
20%
What are the long-term complications of necrotising enterocolitis?
- Development of strictures
- Malabsorption if extensive bowel resection was necessary
Why do preterm infants have an increased risk of infection?
- IgG is mostly transferred across placenta in last trimester, and no IgA and IgM transferred - Infection in or around cervix is often reason for preterm labour, and may cause infection shortly after birth
When do most infections in pre-term infants occur?
After several days
What are infections in pre-term infants often associated with?
- Indwelling catheters
- Artificial ventilation
How long after birth is hypoglycaemia particularly likely?
24 hours of life
What can cause hypoglycaemia in the first 24 hours of life?
- Preterm
- IUGR
- Mothers with diabetes
- Large for gestational age
- Hypothermic
- Polycythaemic
- Ill for any reason
Why can premature and IUGR babies get hypoglycaemia?
Poor glycogen stores
What are the symptoms of neonatal hypoglycaemia?
- Irritability
- Apnoea
- Lethargy
- Drowsiness
- Seizures
Why can many babies tolerate low glucose?
Due to use of lactate and ketones
What glucose level is desirable in neonates?
> 2.6mmol/L
Why is glucose level >2.6mmol/L desirable?
For good neurodevelopment
How can neonatal hypoglycaemia be prevented?
Early and frequent feeding with breast milk
Regular monitoring if at risk
When should an infant be given IV glucose infusion?
2 levels <2.6 or one <1.6
How should high IV concentrations of glucose be administered?
Centrally
Why should high IV concentrations of glucose be administered centrally?
To avoid peripheral skin necrosis
Other than glucose, what else may be given in neonatal hypoglycaemia?
- Glucagon
- Hydrocortisone
Why is hypothermia a problem?
Causes increased energy consumption
What might the increased energy consumption in hypothermia lead to?
- Hypoxia
- Hypoglycaemia
- Failure to gain weight
- Increased mortality
Why are preterm infants vulnerable to hypothermia?
- Large surface area to weight ratio
- Skin is thin and heat permeable
- Little subcutaneous fat for insulation
- Often nursed naked and cannot conserve heat by curling up or generate heat by shivering
Why does a large surface area to weight ratio cause hypothermia?
Greater heat loss than heat generation
How is hypothermia avoided in preterm infants?
Temperature maintained in incubators or with overhead radiant heaters
How do incubators work?
They allow ambient humidity to be provided, which reduces transepidermal heat loss
What episodes are common in very low birthweight infants?
- Apnoea
- Bradycardia
- Desaturation
When are episodes of apnoea, bradycardia, and desaturation common until in preterm infants?
32 weeks gestation
When might apnoea of prematurity cause bradycardia?
When infant stops breathing for >20-30 seconds, or when breathing continues, but against closed glottis
What is the most common cause of apnoea in premature infants?
Immaturity of central respiratory control
What are the other possible causes of apnoea in premature infants?
- Hypoxia
- Infection
- Anaemia
- Electrolyte disturbance
- Hypoglycaemia
- Seizure
- Heart failure
- Aspiration due to GORD
What happens to breathing with gentle physical stimulation in apnoea of prematurity?
Will usually start again after gentle physical stimulation
What treatment may be used in apnoea of prematurity?
- Caffeine
- CPAP
How does caffeine work in apnoea of prematurity?
It is a resp stimulant
When might CPAP be required in apnoea of prematurity?
If episodes are frequency
What does retinopathy of prematurity affect?
Developing blood vessels at the junction of vascularised and non-vascularised retina
What happens to the developing blood vessels in retinopathy of prematurity?
There is vascular proliferation
What might retinopathy of prematurity progress too?
- Retinal detachment
- Fibrosis
- Blindness
What increases the risk of retinopathy of prematurity?
Uncontrolled use of high concentrations of oxygen
What % of very low birthweight infants is retinopathy of prematurity seen in?
35%
What reduces visual impairment in retinopathy of prematurity?
Laser therapy
How is retinopathy of prematurity detected?
The eyes of susceptible preterm infants (<1500g or <32 weeks) are screened every week by ophthalmologist
In what % of very low birth weight infants does severe bilateral visual impairment occur?
1%
Who is intraventricular haemorrhage very common in?
Very low birth weight infants (60-70% of 500-750g)
When does intraventricular haemorrhage present?
First few days of life
How does intraventricular haemorrhage present?
- Apnoea
- Lethargy
- Poor muscle tone
- Sleepiness
- May progress to coma and bulging fontanelle
How is intraventricular haemorrhage managed?
- Correction of acidosis, anaemia, and hypotension
- Fluid treatment
- Reduction of ICP
What is the definitive treatment for intraventricular haemorrhage?
qVentriculoperitoneal shunt
Why do preterm infants have high nutritional requirements?
Because of their rapid growth
Describe the growth of an infant born at 28 weeks?
Double weight in 6 weeks and treble it in 12 weeks (compared to term infants who dont treble until a year)
At what gestational age can infants suck and swallow milk?
35-36 weeks
How will infants under 35-36 weeks gestation need to be fed?
Oro- or nasogastric tube
When should enteral feeds be introduced in preterm babies?
As early as possible
What feed is given in preterm infants?
Breastmilk is preferable, but needs to be supplemented with phosphate and may need supplementation with proteins, calories, and calcium
What might extremely preterm infants be fed on if maternal breast milk is not available in some centres?
Donor breast milk
What is available for preterm babies if formula feeding is required?
Special infant formulas designed to meet the increased nutritional requirements of preterm infants
What is the limitation of formula feeding preterm babies?
Do not provide protection against infection or other benefits of breast milk
What is often required for nutrition in the very immature or sick infant?
Parenteral nutrition
How is parenteral nutrition usually given in the very immature or sick infant?
Through a central venous catheter inserted peripherally (PICC line)
How is infection prevented when using a PICC line for nutrition?
Should pay strict attention to aseptic technique both during insertion and when fluids are changed
What is the risk of PICC lines?
- Significant risk of septicaemia
- Thrombosis of major vein
What is the limitation of giving parenteral nutrition via a peripheral vein?
Extravasation into skin may cause scarring
What is osteopenia of prematurity?
Poor bone mineralisation
Why is osteopenia of prematurity no longer common?
It is prevented with provision of adequate phosphate, calcium, and vitamin D
Why are preterm babies at risk of iron deficiency?
- Iron is mostly transferred to the foetus during the last trimester
- Loss of blood from sampling
- Inadequate erythropoietin response
Describe the use of iron supplements in preterm babies?
They are started at several weeks of age, and continued after discharge home
What are the advantages of breastmilk in the premature infant?
- Provides ideal nutrition for infants during first 4-6 months of life
- Life saving in developing countries
- Reduces risk of GI infection and necrotising enterocolitis
- Enhances mother child relationship
- Reduces risk of diabetes, hypertension, and obesity later in life
- More easily digested than other sources
When is an infant described as having bronchopulmonary dysplasia?
If they still have an oxygen requirement at a post-gestational age of 36 weeks
What causes the lung damage in bronchopulmonary dysplasia?
Pressure and volume trauma from artifical ventilation, oxygen toxicity, and infection
What does the CXR show in bronchopulmonary dysplasia?
Widespread areas of opacification, sometimes with cystic changes
How are babies weaned off artificial ventilation?
CPAP to additional ambient oxygen, sometimes over several months
What may facilitate earlier weaning from the ventilator in premature babies?
Corticosteroid therapy
What is the addition benefit of corticosteroids in premature babies?
May reduce oxygen requirements in short term
What is the limitation of corticosteroids in premature babies?
Concern about increased risk of abnormal neurodevelopment, including CP, limits use to those at highest risk and only short courses are given
What can cause death in RDS?
- Intercurrent infection
- Pulmonary hypertension
- Pneumothorax
What infections are common in RDS?
- Pertussis
- RSV
What % of infants ventilated for RDS develop pneumothorax?
10%
How does ventilation for RDS cause pneumothorax?
Air from overdistended alveoli may track into interstitum, resulting in pulmonary interstital emphysema, or leak into pleural cavity, causing pneumothorax
How is pneumothorax avoided in RDS?
Infants are ventilated at lowest pressure to achieve good oxygenation
How is pneumothorax in premature babies treated?
Chest drain
What % of very low birthweight infants develop CP?
5-10%
What are the most common long term neurodevelopment impairments in premature infants?
Learning difficulties
When does long term neurodeveleopmental issues in premature infants become increasingly evident?
When individual child is compared to peers at nursery or school
What long-term neurodevelopmental issues may arise in premature babies?
Problems with;
- Fine motor skills
- Concentration
- Behaviour problems
- Abstract reasoning
- Processing several tasks simultaneously
