71. Problems of the premature baby Flashcards
A 10-week-old female infant weighing 3.5 kg is scheduled for inguinal
hernia repair. She was delivered prematurely at 34 weeks.
What would you enquire about specifically in your pre-operative assessment?
A detailed history from the parents and the notes is required,
particularly if the child spent any time on the neonatal ICU.
Details of any previous operations.
Time spent on a ventilator.
Any medical conditions or congenital problems diagnosed.
General health since leaving hospital – putting on weight, feeding
(associated breathlessness?).
Special precautions or procedures required eg NG feeding, handling.
Any medications, including oxygen therapy.
Premature babies
Premature babies are defined as those born before 37 weeks’ gestation
and account for about 13% of UK births.
They are susceptible to the following
- Increased risk of congenital abnormalities (especially ‘small for dates’ babies).
- Hyaline membrane disease
- Bronchopulmonary dysplasia
- Patent ductus arteriosus
Intra-ventricular (brain) haemorrhage
Retinopathy of prematurity
Hypoglycaemia
Anaemia
Increased susceptibility to infection
Lack of thermoregulation.
What potential problems are there in anaesthetising her?
- A
A difficult airway should be suspected if there has been prolonged
intubation.
This may be subglottic or be part of a congenital abnormality - B
Previously ventilated neonates can have poorly compliant lungs.
Adjust ventilation to minimise high airway pressures.
Avoid high FiO2.
3.CVS
Fluctuations in blood pressure should be avoided to minimise the risks of
hypoperfusion (and resultant ischaemia) and haemorrhagic cerebral injury.
Access
- Drug metabolism may be impaired due to immature liver and enzyme
systems.
Drug metabolism may be impaired due to immature liver and enzyme
systems.
- Hypoglycaemia should be avoided by:
Minimising the starvation time.
Administering glucose containing i.v. fluids.
Regular monitoring of the serum glucose concentration. - Meticulous attention should be paid to maintaining normothermia.
- The general problems of anaesthetising a baby also apply
What precautions would you take post-operatively?
Post-operative apnoea is a common problem.
Apnoea is significant if >15 seconds or if associated with cyanosis or bradycardia.
An apnoea alarm is mandatory in the post-operative period
CPAP may be helpful by distending the chest wall and triggering stretch
receptors.
How would you provide post-operative analgesia?
The principles of multimodal analgesia should be used.
However:
1. Avoid opioids if possible due to apnoea risk.
- NSAIDs should be used with caution as they reduce renal function by up
to 20% and may affect ductus arteriosus closure in the very young
neonate - Paracetamol dosing intervals are extended due to reduced metabolism.
Paracetamol is given at a dose of 15 mg/kg 8 hourly. - Use local anaesthetic infiltration where possible, e.g. Bupivicaine
2 mg/kg.
General considerations when anaesthetising a baby airway
Airway
The airway is prone to obstruction because the head is relatively large
with a prominent occiput and the tongue is large.
Infants and neonates breathe mainly through their nose.
The epiglottis is large, floppy and U-shaped.
The trachea is short (endobronchial intubation).
The glottis is more anterior and the narrowest part of the airway is at the cricoid ring
Respiratory
Ventilation is diaphragmatic and rate dependent.
Horizontal ribs reduce mechanical advantage.
Closing capacity encroaches into FRC during tidal breathing.
Increased airway resistance (50% nasal).
Cardiovascular
Rate-dependent cardiac output.
Poor ventricular compliance.
Low SVR.
High vagal tone.
Gastrointestinal
Immature enzyme systems until 12 weeks alter drug handling.
Prone to hypoglycaemia.
Renal
Poor thermoregulation
Functionally immature.
Altered sodium and drug excretion.
High surface area : volume ratio.
Minimal fat
Some other definitions . . .
Neonate First 44 weeks post-conceptual age
Premature infant Less than or equal to 37 weeks’ gestation
Neonates First month of life
Infants 1–12 months
Low birth wt Less than or equal to 2.5 kg