Update on Paediatric Neuroanaesthesia
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Transcript of Update on Paediatric Neuroanaesthesia
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Update on Paediatric Neuroanaesthesia
Andrew DavidsonAnaesthetist, Royal Children’s
Hospital
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No more anaesthetists!
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• Common conditions• Anaesthesia issues • Future issues
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Paediatric neurosurgery
• Hydrocephalus – shunts• “Tumours”• Trauma • Vascular malformations• Epilepsy• Encephalocoeles, myelodysplasia• Chiari malformations• Craniosynostosis
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Tumours
• Brain tumours are the most common solid tumours in children
• Majority are infratentorial (60%)– Medulloblastomas, cerebellar astrocytomas,
brainstem gliomas, 4th ventricle ependymomas
• Midbrain (15%)– Craniopharyngiomas, optic gliomas, pituitary
adenomas, hypothalamic tumours
• Hemispheric tumours (25%)– Astrocytomas, oligodendrogliomas, ependymomas,
glioblastomas
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Ganglioglioma
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Posterior fossa craniotomy
• Narrow window from symptoms to death – early surgery
• Often curative, so aim for total resection rather than just debulking
• Prone position– Airway!
• Surgery close to the brainstem
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Epilepsy surgery
• Increasing frequency with better localisation
• Temporal lobectomy• Hemispherotomy • Lesionectomy
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Electrocorticography
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before
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Electrocorticography
• “Normal” conditions– Temperature
– CO2
– Anaesthetic agent: remifentanil and low dose isoflurane
• Be consistent!
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Hemispherotomy
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Hemispherotomy
• Long • Lots of blood loss• Slow to wake up
• Not as bloody as hemispherectomy
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Vagal nerve stimulator
• Indication– not candidates for resection
• Outcome– 50% >50% seizure reduction– <10% seizure freedom– replace battery 5yrs
• Anaesthesia – bradycardia
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Anaesthesia for craniotomy in children
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Access
• Once draped almost impossible to reach most of the child
• Lines must be perfect • At least 2 IV access points• Tend to “over monitor” • Separate TIVA line• Meticulous airway positioning
• Don’t start till your happy
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Blood loss
• Blood loss can be substantial – avoid the “cycle of death”
Blood loss
Rapid transfusion
Hyperkalaemia
Death
Acidosis & hypothermia
Coagulopathy
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Blood loss
Rapid transfusion
Hyperkalaemia
Death
Acidosis & hypothermia
Coagulopathy
“Permissive anaemia”
Hypovolaemia
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Transfusion • Avoiding blood is “good”, but • Anaemia is bad for injured brain
• Theoretical risk versus the big issues– Biggest risk of transfusing is incompatibility
error– Biggest risk from avoiding blood is “getting
behind”
• Ideal transfusion trigger is unknown for paediatric neurosurgery/ neurotrauma
• Transfuse early
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Temperature
• Cold is good in theory • Cold worsens coagulopathy • Cold children are hypotensive
• Children get cold quickly, and get hot quickly
• Hypothermia and trauma – possible benefit if cool early enough and long enough
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Blood pressure
• Hypotension– Reduced CPP– Reduced perfusion – Ischaemia
• Hypertension– Increased flow – Oedema– Increased interstitial fluid – increased gradient
from capillary to neuron
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0 50 100 150 200
Perf
usi
on
Mean blood pressure
Adult
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0 50 100 150 200
Perf
usi
on
Mean blood pressure
Child
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Blood pressure
• Ideal perfusion pressure unknown for children
• Low threshold for blood pressure support
• Noradrenaline or Metaraminol • Avoid excessive propofol or volatile anaesthesia • Beware remifentanil • Beware hypothermia • Optimal filling
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Central lines
• Poor IV access– Intra operative and post operative
• If need frequent post operative bloods (DI risk)• Vasopressors for blood pressure support• Central pressure estimate • ? VAE diagnosis and treatment
• Jugular or femoral
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Which anaesthetic?
• Stable blood pressure• Preserve autoregulation (coupling between flow
and oxygen need) • Wake up quickly and smoothly
• Reduce CMRO2
• Neuroprotection
• Allow electrocorticography
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• The evidence is patchy and contradictory in adults• The evidence is very sparse in children
• Do children really need to wake up quickly? • Avoid emergence delirium
• None are perfect
• Focus on the important and practical, rather than the theoretical fine print
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• Sevoflurane: – good for autoregulation and possibly neuroprotection – but slow awakening after long procedures and bad for
electrocorticography
• Desflurane: – good for awakening – but perhaps not so good for autoregulation
• Isoflurane: – neither good nor bad
• Avoid volatile > MAC
• Nitrous oxide: – mixed evidence but generally bad for autoregulation
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• Propofol: – Good for autoregulation and neuroprotection – But, TIVA algorithms are less accurate in
children, so easier to overdose – hypotension, disrupted autoregulation and slow awakening
• Ketamine: – Traditionally thought to be bad for every reason – But new evidence is contradictory – Good choice for the quick CT scan???
• Remifentanil – Stable & Rapid smooth awakening– Hypotension and rebound pain and hypertension
on awakening
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Fluids
• Renal function has less capacity to adjust• Children are more susceptible to cerebral
oedema with hyponatraemia • 0.9% saline
– Good for tonicity – But rapidly leads to hyperchloraemic acidosis
• Post operative– Beware Diabetes Insipidus– Beware increased antidiuretic hormone secretion
– never use hyptonic fluids, check the electrolytes daily
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Pain• Neurosurgery is painful – but do children need opioids and
are they “safe”
• Audit at RCH • 50 children post craniotomy
• 71% of children received parenteral morphine, • No episodes of significant respiratory depression were noted
• Over the 72 hours the median pain score was 1.3• For most of the time children had little or no pain • However, 42% of children had at least one episode of a pain
score >3
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Post craniotomy pain
• Highly variable • Perhaps worse with posterior fossa craniotomies
• Most children have PCA or continuous morphine initially
• Wide variety of adjunct analgesics
• “Low” incidence of sedation or respiratory depression
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Awake craniotomy
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midline
sylvian
fron
tal
parietal
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hipflexion(1.75)
R trunk flexion& shoulderdepression
(2.5)
thumb ext & wrist
flexion(2.0)
wrist ulnar dev. &
pronation(1.75)
elbow & wristflexion
(2.0)
finger (MCP)flexion(1.75)
finger (MCP)flexion & wrist
ulnar dev.(1.5)
finger (MCP)flexion &
thumb opp.(2.0)
wrist sup.& finger (IP)
flexion(1.25)
wrist extension &
ulnar dev.(1.5)
finger extension &supination
(2.5)
lip & face(2.0)
finger(F2)
sensory
finger(F2,3)
sensory
fingersensory
finger(F4,5)
sensory
sensorimotor mapping midline
sylvian
fron
tal
parietal
MF1 = ankle dorsiflexion + hip/trunk/head movement (2.5)MF2 = hip, trunk & head movement to R (2.5)
elbowflexion &
shoulder abd. (3.0)
elbowsensory
armsensory
shoulder depression
& head turn R(3.0)
elbow flexion & shoulderposterior
(3.5)
R trunk flexion
(3.0)
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undercut
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Awake craniotomy in children
• Mature & motivated children
• Familiarization with environment and the team• Favourite music• Use the parents
• Asleep for lines, urinary catheter, scalp blocks and pins• Wide awake to get comfortable on table then fix mayfield• Remifentanil & very low dose propofol sedation
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Intraoperative MRI
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Summary – key messages
• Secure everything before they drape• Low threshold for central lines• Ideal anaesthetic unknown • Ideal blood pressure unknown, but avoid
hypotension • Ideal transfusion trigger unknown, but
transfuse early