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Anaesthesia for MEP use intraoperatively. R3 鄭淳心. Case: A 27y/o male was a case of C7-T1 intramedullary spinal tumor, and he was scheduled for spinal tumor excision via posterior approach. Transcranial stimulation motor evoked potentials was used intraoperatively.
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Case: A 27y/o male was a case of C7-T1 intramedullary spinal tumor, and he was scheduled for spinal tumor excision via posterior approach. Transcranial stimulation motor evoked potentials was used intraoperatively. Past history: nothing particular
Spinal surgery: • Intubation • Prone position • Monitor • Free from pressure: eyes, nose, ear, genitalia • Endo fixation
EP (Evoked potentials) • SSEP(somatosensory evoked potentials ) • Wake-up test • Motor evoked potentials • (false positive results)
Evoked potentials • Anesthetics • Temperature • Hypotension • Hypoxia • Anemia • Pre-existing neurological lesions
Temperature • EMG response decrease • 8.0%/C muscle • 4.1%/C skin • no correlation • keep the same temperature
Anesthetic agents • Inhalation agents • IV-agents Propofol Etomidate Methohexital Thiopental • Ketamine-based anesthesia • With or without propofol
Propofol inhibits motor-evoked potentials induced by transcranial electrical stimulation in a dose- dependent manner • If a train of pulses is used for transcranial stimulation, propofol can be effectively used as a supplement to ketamine- based anesthesia during intraoperative monitoring of myogenic motor-evoked potentials • Addiction of propofol significantly reduced the ketamine-induced psychedelic effect including unpleasant dreaming and hallucination.
Formula 1 • Ketamine 1-2 mg/kg/hr • Fentanyl • 50% nitrous oxide in oxygen • Vecuronium 0.04 mg/kg/hr • Propofol 1-3 mg/kg/hr • Nicardipine if SBP>150mmHg
Formula 2 (’96 BJA) • Methohexitone 2mg/kg for hypnosis 0.1mg/kg/min for 30 min 3-4.5 mg/kg/hr • Alfentanil 50 ug/kg 300ug/kg/hr for 15min 60ug/kg/hr • Ketamine 1.2 mg/kg/hr for 1hour 0.84 mg/kg/hr • muscle relaxant bolus
our formula • Ketamine 2mg/kg/hr • Alfentanil 20ug/kg/hr • Esmeron 6mg/hr • Propofol 75mg/hr (1.5mg/kg/hr)
Maintain anesthesia depth (microsurgery) • BP control: nicardipine