75. Squint surgery Flashcards
A 4-year-old boy is on your theatre list for squint surgery. You visit the
ward pre-operatively and find the mother by the bed and the child
playing in the playroom.
How do you approach your assessment?
It is important to establish a rapport with both the child and the mother. The
mother, in particular, is likely to be extremely anxious. It is an opportunity to
assess the child for anaesthesia, answer questions and address any anxieties.
The options for induction of anaesthesia and post-operative analgesia should
also be discussed.
Do you go and see the child or leave him playing?
Most of the information can be obtained from the mother, but a useful
assessment of the child can be gained from a distance, observing how he
interacts and whether his behaviour and physical skills are appropriate for his
stage of development.
It is important to directly interact with the child at
some point and to perform a physical examination.
If the child is happier in
the playroom, then take the mother to the playroom. The child is not
disturbed, but still gets some contact with you. Getting down to the child’s
level is also important.
What associations are there with squint
Cerebral palsy
Noonan’s syndrome (key points: cardiac defects, difficult intubation, platelet
and coagulation defects, renal dysfunction).
Down’s syndrome
Hydrocephalus
Malignant hyperpyrexia.
What information do you want from mum?
The usual medical and anaesthetic history, including details of
Gestational age
Birth and neonatal problems
Milestones
Recent vaccinations
Any recent coughs or colds
Try to get an idea of whether a sedative pre-med will be needed.
Obtain consent for and explain rectal analgesia
What information do you give her?
Brief explanation of ‘the journey’ through the theatre complex.
Include an explanation of what will happen if
The child gets upset
Failed cannulation.
Who will escort the parent from the anaesthetic room.
Details of post-operative analgesia (including suppositories) are important
to allay anxiety.
What other methods are there of explaining anaesthesia?
Optimum choice depends on the intellectual ability of the child.
Leaflets
Videos
Pre-op visits and clinics.
Tell me about fasting times for children prior to surgery?
Solids – 6 hours
Formula milk – 6 hours
Breast milk – 4 hours
Clear fluids – 2 hours
Breast milk is more easily absorbed (4 hours fasting time).
Formula milk should be considered as a solid, as should sweets and chewing
gum (6 hours fasting time).
Children and fasting
Children are positively encouraged to have clear fluids right up to
2 hours before surgery.
Rapid fluid turnover and high metabolic rate makes dehydration and
hypoglycaemia more likely in the fasting child than potential
aspiration.
Children who have had unrestricted clear fluids until 2 hours prior to
surgery have residual gastric volumes equal to or less than those fasted
overnight.
Good hydration may reduce post-operative nausea and vomiting.
How would you anaesthetise him?
Unless the history pointed towards one particular technique, describe your
chosen method. For example:
Establish routine monitoring.
i.v. access following prior use of EMLA cream.
Induction with i.v. fentanyl 1 mcg/kg and propofol 3 mg/kg.
Maintain an airway with an appropriate LMA.
Maintenance: spontaneously breathing in oxygen, air and sevoflurane.
Can your anaesthetic influence the surgery?
Suxamethonium increases the ocular tone for up to 20 minutes.
This can make surgical correction difficult.
Controlling CO2 helps control the intra-ocular pressure.
Reducing the ET CO2 reduces the incidence and severity of the oculocardiac reflex.
Ensure sufficient depth of anaesthesia to achieve neutral gaze.
What potential complications are associated with the surgery?
Bradycardia via the oculocardiac reflex (Aschner phenomenon). Not helped
by high vagal tone in children.
High incidence of post-operative nausea and vomiting (PONV).
The oculocardiac reflex
Traction on the extra-ocular muscles or pressure on the eyeball results
in arrhythmias, in particular bradycardia but VEs, sinus arrest or VF
may also occur.
Afferents via ophthalmic division of trigeminal nerve (V) to reticular
formation and visceral motor nucleus of vagus nerve (X).
Efferents via the vagus nerve (X) to sino atrial node.
Do anticholinergics given prophylactically prevent the oculocardiac
reflex?
Atropine and glycopyrrolate both obtend the oculocardiac reflex if given
prophylactically.
How would you avoid PONV?
General measures
Haemodynamic stability
Control of oxygenation
Adequate hydration.
Technique
Avoidance of paralysis and neostigmine
Avoidance of nitrous oxide (controversial)
Avoid intubation
Avoid opioids.
Prophylaxis
Combination therapy with agents such as ondansetron 0.1 mg/kg and
dexamethasone 0.1 mg/kg.
It has been suggested that the oculocardiac reflex predisposes to PONV and
preventing its occurrence reduces the incidence of PONV.
How would you treat post-operative pain?
This is usually mild and treated with a combination of local anaesthetic
drops and simple analgesics.
Paracetamol 40 mg/kg rectally or 20 mg/kg orally to load
Brufen or voltarol
Opioids can usually be avoided
Regular paracetamol and NSAID post-operatively.
Topical NSAID drops may also be used.
