71. Problems of the premature baby

Question 1

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?

Answer 1

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.

Question 2

Premature babies

Answer 2

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

1. Increased risk of congenital abnormalities (especially ‘small for dates’ babies).
2. Hyaline membrane disease
3. Bronchopulmonary dysplasia
4. Patent ductus arteriosus

Intra-ventricular (brain) haemorrhage

Retinopathy of prematurity

Hypoglycaemia

Anaemia

Increased susceptibility to infection

Lack of thermoregulation.

Question 3

What potential problems are there in anaesthetising her?

Answer 3

1. A
   A difficult airway should be suspected if there has been prolonged
   intubation.
   This may be subglottic or be part of a congenital abnormality
2. 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

4. Drug metabolism may be impaired due to immature liver and enzyme
   systems.

Drug metabolism may be impaired due to immature liver and enzyme
systems.

5. Hypoglycaemia should be avoided by:
   Minimising the starvation time.
   Administering glucose containing i.v. fluids.
   Regular monitoring of the serum glucose concentration.
6. Meticulous attention should be paid to maintaining normothermia.
7. The general problems of anaesthetising a baby also apply

Question 4

What precautions would you take post-operatively?

Answer 4

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.

Question 5

How would you provide post-operative analgesia?

Answer 5

The principles of multimodal analgesia should be used.
However:
1. Avoid opioids if possible due to apnoea risk.

2. 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
3. Paracetamol dosing intervals are extended due to reduced metabolism.
   Paracetamol is given at a dose of 15 mg/kg 8 hourly.
4. Use local anaesthetic infiltration where possible, e.g. Bupivicaine
   2 mg/kg.

Question 6

General considerations when anaesthetising a baby airway

Airway

Answer 6

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

Question 7

Respiratory

Answer 7

Ventilation is diaphragmatic and rate dependent.

Horizontal ribs reduce mechanical advantage.

Closing capacity encroaches into FRC during tidal breathing.

Increased airway resistance (50% nasal).

Question 8

Cardiovascular

Answer 8

Rate-dependent cardiac output.

Poor ventricular compliance.

Low SVR.

High vagal tone.

Question 9

Gastrointestinal

Answer 9

Immature enzyme systems until 12 weeks alter drug handling.

Prone to hypoglycaemia.

Question 10

Renal

Poor thermoregulation

Answer 10

Functionally immature.
Altered sodium and drug excretion.

High surface area : volume ratio.
Minimal fat

Question 11

Some other definitions . . .

Answer 11

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