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Neuroanaesthesia update

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Talk delivered in Adelaide, Australia in 2015 at a national ANZCA conference for anaesthestists

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Neuroanaesthesia update

  1. 1. UPDATE IN NEUROANAESTHESIA DOUGLAS FAHLBUSCH MBBS, FANZCA, GDM, GAICD WWW.PERIOPERATIVE.COM.AU Improving cost, risk and the healthcare experience MAY 2015 1
  2. 2. INTRODUCTION • Neuroscience underpins • Neuroanaesthesia and • Neurocritical care • ‘… advance the art and science of the care of the neurologically impaired patient through education, training and research in perioperative neuroscience’ 2 SNACC, RCOA
  3. 3. OVERVIEW PRACTICAL UPDATE • Brain: defines who we are • Loss of function defines death • Function routinely manipulated in anaesthesia • Critical considerations when operating on this target organ Gelb AW 2015 • What’s not new • Surgical trends • Cerebral oximetry • Intraoperative CT • Pursuit of excellence 3
  4. 4. RECURRENT ISSUES WHAT’S NOT NEW • Patient positioning • Neurophysiologic monitoring • Intravenous fluid management • Arterial blood pressure target • PaCO2 target • Hypothermia • Control of intracranial pressure/ brain relaxation • Use of steroids • Use of osmotherapy Miller 8th Edn, Ch 70 • Use of diuretics • Use of anticonvulsants • Pneumocephalus • Venous air embolism • Glucose management • Emergence from anaesthesia 4
  5. 5. WHAT’S NOT NEW CEREBRAL PHYSIOLOGY • Cerebral metabolic rate (CMR) is high: • 60% function, 40% cellular homeostasis • 15% of cardiac output • Cerebral blood flow (CBF) is ~50 mL/100 g/min • grey 80%, white 20% • CBF and local metabolism highly coupled over MAP 65- 150 mmHg (est), else passive 5Miller 8th Edn, Ch 17
  6. 6. WHAT’S NOT NEW CBF AUTOREGULATION • Chemical regulation • PaCO2 range of 25 to 70 mm Hg direct effect on CBF • PaO2 < 60 mm Hg CBF decreases dramatically • Temperature affects metabolic rate primarily, CBF secondarily • Systemic vasodilators affect the cerebral circulation and can, depending on the MAP, increase CBF • Vasopressors affect arterial blood pressure - CBF secondarily 6Miller 8th Edn, Ch 17
  7. 7. WHAT’S NOT NEW SELECTION OF ANAESTHETICS • Intravenous • Barbiturates, etomidate, and propofol decrease the CMR • Opiates and benzodiazepines effect minor decreases in CBF and CMR • Ketamine can significantly increase the CMR and therefore CBF • Volatiles reduce CMR • above 1 MAC increase CBF • reduce/ omit if brain ‘tight’ 7Miller 8th Edn, Ch 17
  8. 8. WHAT’S NOT NEW CEREBRAL ISCHAEMIA • Barbiturates, propofol, ketamine, volatile anaesthetics, xenon neuroprotective • animal models, mild ischaemic insult • not with moderate-to-severe injury (delays apoptosis) • Etomidate can decrease regional blood flow, can exacerbate ischaemia • Brain stores of O2/ substrates limited, extremely sensitive to decr CBF • Severe decreases in CBF = rapid neuronal death • early excitotoxicity, and delayed apoptosis 8Miller 8th Edn, Ch 17
  9. 9. CONTROL OF INTRACRANIAL PRESSURE/ BRAIN RELAXATION Miller 8th Edn, Table 70-1 & Box 70-3 (often overlooked) JVP -> AWP -> PCO2 & O2 -> ABP -> CMRO2 -> vasodilators -> mass lesions 10
  10. 10. SURGICAL TRENDS • Minimally invasive procedures • Transphenoidal • DBS • Intraventricular • Discectomy 11
  11. 11. GUIDELINES FOR PERCUTANEOUS ENDOSCOPIC SPINAL SURGERY • Lumbar, Thoracic, Cervical disc herniations • Lateral spinal canal/ foraminal stenoses • Degen facet joint cysts with radiculopathy • Symptomatic central stenosis (experienced hands) • C/I • Cauda equina • Instabilities/ deformities/ non-neural back pain • Very large herniations relatively C/I ISMISS 2010 12
  12. 12. TRANSFORAMINAL ENDOSCOPIC DISCECTOMY Michael Y Wang, MD FACS; Professor, Departments of Neurological Surgery & Rehab Medicine, University of Miami Miller School of Medicine 13
  13. 13. ENDOSCOPIC SPINAL SURGERY • Duration 45-80 mins, • LA 1.9 mg/kg • ‘Discomfort’ - ok if nerve roots avoided • Discharge < 24 hrs possible (Chan) 14 Surg Neurol Int. 2014; 5(Suppl 3): S62–S65
  14. 14. ENDOSCOPIC SPINAL SURGERY • LA/ sedation has been used since 1926 (Towne) • Well-tolerated (Hsien-Te Chen) • Indicated for multiple comorbidities (Khan), ASA I-IV, geriatrics • Intraop evaluation of surgical progress • Early discharge • The future ‘gold standard’ for discectomy? (Gibson 2012) 15
  15. 15. DBS STEREOTACTIC SCAN PREOP • > 50 cases (Matthew McDonald, Neurosurgeon Calvary Wakefield) • Propofol/ LA for placing frame (+/- opioid for tremor suppression) • Avoid benzo’s 16 Picture courtesy of A/Professor Wilcox, FMC
  16. 16. DBS THEATRE SETUP • Dexmedetomidine infusion • Propofol ceased once scalp reflected 17 Picture courtesy of A/Professor Wilcox, FMC
  17. 17. Picture courtesy of A/Professor Wilcox, FMC DBS INTRAOP 18
  18. 18. DBS BATTERY/ LEADS • LMA • Propofol • Fentanyl • Volatile • Battery most commonly right on men and left on women (seatbelts) 19
  19. 19. EQUIPMENT TRENDS • Cerebral oximetry • Intraoperative CT 20
  20. 20. INTRACRANIAL MONITORING Near-Infrared oximetry ICP (ventricular or parenchymal) Brain tissue oximetry Jugular venous oximetry Microdialysis 21
  21. 21. NEAR INFRARED SPECTROSCOPY • Two wavelengths • Substract superficial tissues • Left with deep tissue signal • Non-pulsatile • Ratio of arterial to venous blood dictates ‘saturation’ • Multiple sites (cerebral, kidneys, thigh) 22
  22. 22. NEAR INFRARED OXIMETRY • Relative indices of perfusion • Baseline set pre- induction (usu. 58-82) • Relative decline < 20% ok • Absolute thresholds • 50 intervene • 40 critical 23 up to 6 channels
  23. 23. NEAR INFRARED SPECTROSCOPY 24 • Perioperative morbidity not correlated with cerebral desaturation • Reassurance for • elderly, paeds • vasculopaths • ACDF, carotids Cowie et al 2014 (AIC)
  24. 24. INTRAOP CT ‘O-ARM’ 25
  25. 25. INTRAOP CT USES - DBS • Confirm stimulator placement & track • Exclude bleeding 26
  26. 26. INTRAOP CT USES - SPINAL FUSION • screw placement • alignment • bleeding 27
  27. 27. CONCLUSION • Interplay of CNS with other organ systems/ physiology/ pathology • Unit Excellence: • Staff training, retention • Cross-functional processes (breaking down the silos) • IT: increase reach and engagement • Closed loop delivery systems: anaesthesia, fluids … 28 Puri 2015
  28. 28. FURTHER INFORMATION • Neuroanaesthesia SIG - ANZCA/ ASA/ NZSA • Neuroanaesthesia Society of Great Britain and Ireland https://nasgbi.org.uk/ • Royal College of Anaesthetists http://www.rcoa.ac.uk/document- store/guidance-the-provision-of-services-neuroanaesthesia-and- neurocritical-care-2015 • Society for Neuroscience in Anesthesiology and Critical Care http://www.snacc.org/# • Perioperative Solutions www.perioperative.com.au • Dr Douglas Fahlbusch - drfahlbusch@perioperative.com.au 29
  29. 29. 1. Gelb AW. Actualización en neuroanestesia. Rev Colomb Anestesiol. 2015;43:1-2. 2. Gibson JNA, et al. Transforaminal endoscopic spinal surgery: The future ‘gold standard’ for discectomy? A review, The Surgeon (2012) 3. Hsien-Te Chen et al. Endoscopic discectomy of L5-S1 disc herniation via an interlaminar approach: Prospective controlled study under local and general anesthesia. Surg Neurol Int. 2011; 2: 93. 4. Khan MB et al. Thoracic and lumbar spinal surgery under local anesthesia for patients with multiple comorbidities: A consecutive case series. Surg Neurol Int. 2014; 5(Suppl 3): S62– S65. 5. Li ZZ et al. The strategy and early clinical outcome of full-endoscopic L5/S1 discectomy through interlaminar approach. Clin Neurol Neurosurg. 2015 Mar 14;133:40-45 6. Miller RD (Ed). Miller’s Anesthesia. 8 Edn. Reed Elsevier 2014 7. Peng CWB et al. Percutaneous endoscopic lumbar discectomy: clinical and quality of life outcomes with a minimum 2 year follow-up. Journal of Orthopaedic Surgery and Research 2009, 4:20 8. Puri et al. A Multicenter Evaluation of a Closed-Loop Anesthesia Delivery System: A Randomized Controlled Trial.Anesth Analg. 2015 Apr 21 9. Towne EB. Laminectomy and removal of spinal cord tumors under local anesthesia. Cal West Med. 1926;24:194. References 30

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