Update on Paediatric Neuroanaesthesia

1. Update on Paediatric Neuroanaesthesia Andrew Davidson Anaesthetist, Royal Children’s Hospital

2. No more anaesthetists!

3. Common conditions • Anaesthesia issues • Future issues

4. Paediatric neurosurgery • Hydrocephalus – shunts • “Tumours” • Trauma • Vascular malformations • Epilepsy • Encephalocoeles, myelodysplasia • Chiari malformations • Craniosynostosis

5. 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

6. Ganglioglioma

7. 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

8. Epilepsy surgery • Increasing frequency with better localisation • Temporal lobectomy • Hemispherotomy • Lesionectomy

9. Electrocorticography

10. before

11. Electrocorticography • “Normal” conditions • Temperature • CO2 • Anaesthetic agent: remifentanil and low dose isoflurane • Be consistent!

13. Hemispherotomy

14. Hemispherotomy • Long • Lots of blood loss • Slow to wake up • Not as bloody as hemispherectomy

15. Vagal nerve stimulator • Indication • not candidates for resection • Outcome • 50% >50% seizure reduction • <10% seizure freedom • replace battery 5yrs • Anaesthesia • bradycardia

16. Anaesthesia for craniotomy in children

17. 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

18. Rapid transfusion Hyperkalaemia Acidosis & hypothermia Blood loss Coagulopathy Death Blood loss • Blood loss can be substantial – avoid the “cycle of death”

19. “Permissive anaemia” Hypovolaemia Rapid transfusion Hyperkalaemia Acidosis & hypothermia Blood loss Coagulopathy Death

20. 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

21. 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

22. Blood pressure • Hypotension • Reduced CPP • Reduced perfusion • Ischaemia • Hypertension • Increased flow • Oedema • Increased interstitial fluid – increased gradient from capillary to neuron

23. Adult Perfusion Mean blood pressure

24. Child Perfusion Mean blood pressure

25. 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

26. 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

27. Which anaesthetic? • Stable blood pressure • Preserve autoregulation (coupling between flow and oxygen need) • Wake up quickly and smoothly • Reduce CMRO2 • Neuroprotection • Allow electrocorticography

28. 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

29. 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

30. 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

31. 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

32. 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

34. 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

35. Awake craniotomy

37. midline frontal parietal sylvian

39. sensorimotor mapping midline MF1 = ankle dorsiflexion + hip/trunk/head movement (2.5) MF2 = hip, trunk & head movement to R (2.5) R trunk flexion& shoulderdepression(2.5) hipflexion(1.75) shoulder depression & head turn R(3.0) R trunk flexion(3.0) elbow flexion & shoulderposterior (3.5) elbowflexion &shoulder abd. (3.0) thumb ext & wristflexion(2.0) elbow & wristflexion(2.0) frontal wrist ulnar dev. &pronation(1.75) wrist extension & ulnar dev.(1.5) finger (MCP)flexion(1.75) elbowsensory finger extension &supination(2.5) finger (MCP)flexion & thumb opp.(2.0) finger (MCP)flexion & wristulnar dev.(1.5) wrist sup.& finger (IP) flexion(1.25) finger(F4,5)sensory armsensory parietal finger(F2)sensory finger(F2,3)sensory fingersensory lip & face(2.0) sylvian

40. undercut

41. 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

43. Intraoperative MRI

44. 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