17.10 Prematurity

Question 1

A 12-week-old male baby presents for a unilateral inguinal hernia repair. He was born at 30 weeks
gestation (30/40).

a) What are the specific perioperative concerns in this baby? (11 marks)

Answer 1

Airway:
» Complications of previous prolonged intubation:

tracheomalacia or subglottic stenosis.
Risk of difficult intubation or need
for smaller tube diameter.

Respiratory:

1. > > Bronchopulmonary dysplasia:
   alveoli and surfactant development still
   ongoing at the time of this baby’s birth and he may therefore have required ventilatory support.

More than four weeks ventilation/oxygen
treatment results in risk of bronchopulmonary dysplasia due to volutrauma, barotrauma, oxygen toxicity.

Outcome: reduced lung compliance, increased
oxygen requirement, obstructive lung disease with a reactive component.

2&raquo_space; Apnoeas:
risk of obstructive,
central and mixed apnoeas
(cessation of breathing of more than
20 seconds or loss of effective
breathing with bradycardia).

Central apnoeas occur due to reduced
chemoreceptor sensitivity,
reduced central response to hypoxaemia and hypercapnia, and change in the response to

hypoxaemia
(apnoea only instead of the
normal hyperventilation followed by apnoea).

Perioperative factors such as anaesthetic agents, opioids and hypoxia increase the risk,
as do stress and sepsis.
Risk persists until 60 weeks post-conception.
Common in the first 12 hours postoperatively,
may continue up to 72 hours postoperatively. Necessitates overnight admission for observation.

3. > > Respiratory fatigue: young babies can only increase minute ventilation by increasing respiratory rate.
   Hypoglycaemia and reduced proportion of
   type I muscle fibres in diaphragm make fatigue more likely.

Cardiovascular:
1.&raquo_space; Increased risk of all cardiac defects
and delayed closure of ductus arteriosus.

2. > > Difficulty cannulating due to
   multiple previous cannulations

Neurological:
» Premature babies are at
significant risk of intraventricular haemorrhage –
this baby may suffer the consequences of this such as cerebral palsy or hydrocephalus.

Endocrine:
» Reduced glycogen stores in
conjunction with preoperative starvation
may result in hypoglycaemia.

Excessive starvation must be avoided and
consideration given to glucose supplementation.

Pharmacology:
» Altered liver and renal handling
of drugs due to immaturity.

Gastrointestinal:
» Reflux is common due to underdevelopment of gastro-oesophageal sphincter, thus increasing the risk of aspiration and apnoeas.

Haematological:
» Risk of anaemia related to previous
frequent blood sampling.

Metabolic:
» All babies have high risk of hypothermia,
but an ex-premature baby
is at even greater risk due to paucity of subcutaneous fat, immature thermogenesis due to reduced brown fat, and increased surface-areato- volume ratio. The consequences may be greater, too, with risk of
apnoeas and hypoglycaemia.

Question 2

b) What are the options for anaesthesia? (4 marks)

Answer 2

General anaesthesia:

> > Rapid sequence induction
(rarely indicated) or standard intubation.

Gas induction may offer better control
and reduced risk of desaturation over
intravenous induction.

Positive pressure ventilation to reduce fatigue.

> > Caudal analgesia or local infiltration by surgeons may reduce opioid requirements,
thus reducing the risks of apnoeas and unpredictable
effects due to immaturity of liver and kidneys.

Spinal anaesthesia:
» Caudal analgesia in addition may increase postoperative analgesia.

> > Ideally, sedatives should be avoided.

Caudal anaesthesia:
» Rarely used alone, short duration of anaesthesia.

Question 3

c) Discuss the advantages and disadvantages of general anaesthesia for this baby. (5 marks)

Answer 3

Advantages:
» Regional anaesthesia may produce suboptimal operating conditions in moving baby.

> > Use of sedatives to improve operating conditions when using regional anaesthesia may increase the risk of postoperative apnoeas in an ex-premature baby.

________________________________________________

Disadvantages:
» Possible difficult airway due to previous intubations.

> > Increased risk of periods of desaturation such as at induction, with consequent risks of hypoxaemia.

> > Ideally, general anaesthesia to be avoided in an oxygen-dependent baby with severe lung disease.

> > General anaesthesia does not have the inherent postoperative analgesic effects of a regional technique.

> > Some evidence suggests increased risk of postoperative apnoeas after general anaesthesia.

> > Excessive positive pressure ventilation may result in exacerbation of right to- left shunt or further barotrauma in already damaged lungs.