Anaesthesia for paediatric neurosurgery

Question 1

Infant Fontanelle closure

Answer 1

Anterior- 12-18months
Posterior- 2-3months

Question 2

Cerebral Perfusion Pressure in paediatrics

Answer 2

CPP= MAP - ICP (or CVP whichever is higher)

ICP values
Paediatrics <15mmHg
Neonates 2-6mmHg

Question 3

Cerebral blood flow of neonate, infant, child and adult (ml/min/100g)

Answer 3

Neonate: 40-42ml/min/100g
Infant: 90ml/min/100g
Child: 100ml/min/100g
Adult: 50ml/min/100g

Question 4

CFx of raised ICP in paediatrics

Answer 4

• Increasing head circumference
• Bulging fontanelle
• N&V
• Papilledema
• Headaches
• Lethargy
• Reduced GCS
• Changes in pupils
• Loss of upward gaze

Question 5

Pre-operative assessment of paediatric patients undergoing neurosurgery

Answer 5

• CV Examination- any cardiac anomalies that may increase the risk of VAE
• If vomiting beware dehydration and deranged electrolytes
• FBC, U&Es
• LFTs and coag (esp if on anticonvulsants)

Question 6

Induction and maintenance options for paediatric neurosurgery

Answer 6

• Any technique that reduces the risk of a distressed child causing spikes in ICP is acceptable therefore Gas and IV induction is fine
• Avoid N2O as it increases cerebral blood volume
• Sevoflurane has the least effect on autoregulation of CPP
• TIVA is ideal for cases where neuromonitoring is required

Question 7

Recommended intraoperative monitoring for paediatric neurosurgery

Answer 7

• SpO2, ECG, BP, ETCO2
• CVP not routinely required- if using consider where to put it as may impede venous drainage
• Temperature monitoring
• Urethral catheter- most procedures long, need to monitor for risk of DI
• Depth of anaesthesia monitoring- if able

Question 8

Why are children more at risk of venous air embolism

Answer 8

• Larger heads, often above the level of the heart
• The head has a greater proportion of body surface area
• Diploic veins and venous sinuses are less collapsible making it easier for air to be entrained

Question 9

Dose of hypertonic saline to reduce ICP

Answer 9

3ml/kg of 3% NaCl

Question 10

Causes of paediatric hydrocephalus

Answer 10

Congenital
- Chiari malformation
- Meningomyelocele
- Aqueduct stenosis

Acquired
- Following SAH, intraventricular haemorrhage
- Tumours- especially in the posterior fossa
- Infections- meningitis

Question 11

Anaesthetic considerations for paediatric patients having posterior fossa surgery

Answer 11

• Usually due to tumours causing obstruction and hydrocephalus
• Normally done prone but can be done sitting- in sitting position VAE risk is high, tube displacement risk high, patients also often have head flexed which can cause issues with venous drainage
• Rapid changes in HR and BP or arrhythmia intra-op should warn surgeon they are working near critical brainstem nuclei
• ## Bulbar dysfunction can occur post-op so an NG tube may be necessary

Question 12

Surgical options for controlling epilepsy

Answer 12

• Vagal nerve stimulator
• Resection of mapped epileptic foci
• Hemispherectomy
• Corpus callosotomy (disconnection of the two hemispheres)
• Temporal lobe resection