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Anesthesia and Intraoperative
Neurological MonitoringDavid Ferson, M.D.
Department of AnesthesiologyDepartment of NeurosurgeryM. D. Anderson Cancer Center
Lecture Outline
� Neuroanatomy and neurophysiology
� Modern imaging and navigation techniques
� Anesthetic agents and their effects on neurological monitoring
� Future directions
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Modern Imaging - Tractography
Modern Imaging - Tractography
Preoperative Surgical Planning
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Constant current generator producing a train of square wave, biphasic pulses of 1 ms phase duration at frequency of 60 Hz.
Ojemann stimulator (bipolar electrode with 5mm spacing).
SSEPs and CMEPs
Upper extremity
Lower extremity
Intraoperative EP Monitoring Gold Standard for Functional Mapping
Childs Nerv Syst. 2002 Jul;18(6-7):264-87. Epub 2002 Jun 13.Intraoperative neurophysiological monitoring in pediatric neurosurgery: why, when, how?Sala F, Krzan MJ, Deletis V.
sensory
motor
Cortical Mapping
motor sensory
TIBIAL SSEP – KNEE STIMULATION
contact 1 contact 5
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motor sensory
TIBIAL SSEP – ANKLE STIMULATION
Childs Nerv Syst. 2002 Jul;18(6-7):264-87. Epub 2002 Jun 13.Intraoperative neurophysiological monitoring in pediatric neurosurgery: why, when, how?Sala F, Krzan MJ, Deletis V.
Anesthetic Agents� Intravenous
� Benzodiazepins [Midazolam]� Barbiturates [Sodium Thiopental]� Opiods [Morphine, Fentanyl, Sufentanil, Remifentanil ]� Propofol� Etomidate� Ketamine� Dexmetetomidine� Neuromuscular Blocking Agents (NMBA)
� Inhalational� Halogenated agents� Nitrous oxide
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Insensitive to Anesthetics/Insensitive to
NMBA
BAEP, D WAVES, ?SUBCORTICAL SSEP
Agent Notes
Inhalational agents Little effectHigh doses suppresses subcortical SSEP
Intravenous agents Little effect
Sensitive to Anesthetics/Sensitive to NMBA
CORTICAL SSEP, MUSCLE MEP
Agent Notes
Inhalational agents Reduce amplitude even at low doses, MEP> SSEP
Midazolam, Thiopental At low dose reduce MEP amplitudeAt moderate doses reduce SSEP amplitude
Propofol Slight reduction of MEP/SEP amplitude (dose dependent)
Opioids No significant affect
Ketamine, Etomidate
Dexmetetomidine
Increase amplitude
BAEP, Cortical (P25-N35) – no effect,� Amplitude median nerve P15-N20
NMBA Obliterate MEPLow dose may allow monitoring (TOF 2/4)
Sensitive to Anesthetics/Insensitive to
NMBACORTICAL SSEP
Agent Notes
Inhalational agents ProblematicRestricted to < 0.5 MACDesflurane and Sevoflurane better
Nitrous oxide ProblematicMay be combined with intravenous anesthetic
Midazolam, Thiopental Amplitude suppression (0.2 µg/kg)
Propofol, Thiopental Mild amplitude suppression
Opioids No significant affect
Ketamine, Etomidate
Dexmetetomidine
Increase amplitude
BAEP, Cortical (P25-N35) – no effect,
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Insensitive to Anesthetics/Sensitive to NMBA
EMG
Agent Notes
Inhalational agents Little effect
Intraveneous agents Little effect
NMBA Obliterate EMGLow dose may allow monitoring (TOF 2/4)
Anesthetic Paradigmsfor Neuromonitoring
SSEP Monitoring
Halogenated inhalational agents (<0.5 MAC)
Opioid (Remifentanil 0.05-2mcg/kg/min)
±Ketamine or EtomidateDexmetetomidine (0.1-0.7 mcg/kg/hr)
± NMBA
SSEP/MEP Monitoring
Propofol infusion (<150 mcg/kg/min)Dexmetetomidine (0.1-0.7 mcg/kg/hr)
Opioid (Remifentanil 0.05-2mcg/kg/min)
±Ketamine or etomidate
EMG Monitoring
Inhalational agent
Intravenous anesthetic agents
± NMBA (maintain at least TOF 2/4)
EEG Monitoring
Halogenated inhalational agents (<0.5 MAC)
Nitrous/narcotic technique
± NMBA
BAEP Monitoring
Inhalational agent
Intravenous anesthetic agents
Future Directions� New imaging techniques
� Intraoperative MRI
� Intraoperative Navigation
� Intraoperative stimulation and correlation of neurological function
� Great research opportunities
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Stereotactic and Functional Neurosurgery, 2009
THANK YOU