title: Intraoperative motor-evoked potential monitoring in scoliosis surgery: comparison of desflurane/nitrous oxide with propofol total intravenous anesthetic regimens.
abstract: METHODS
  A prospective, randomized study in a large general hospital setting.
  
  
  BACKGROUND
  During spinal surgery, monitoring motor-evoked potentials (MEPs) is a means of assessing the intraoperative integrity of corticospinal pathways. However, MEPs are known to be sensitive to the effects of anesthetic agents.
  
  
  OBJECTIVE
  To compare the use of desflurane or total intravenous anesthetic regimens (TIVA) with multipulse cortical stimulation for intraoperative monitoring (IOM).
  
  
  METHODS
  Twenty consecutive patients (10 in each arm) undergoing scoliosis correction surgery were randomly assigned to 2 equal groups receiving desflurane or TIVA. Inhalational anesthesia was maintained using 66% nitrous oxide in oxygen and a mean end-tidal desflurane concentration of 3.4%. For TIVA, continuous intravenous infusion of propofol was used. For analgesia, fentanyl and morphine were given when required for both groups. Cortical stimulation was achieved with 2 bipolar direct current stimulators connected in parallel by jumper cables. Five equivalent pulses 0.5 ms in duration at 4 ms intervals were delivered at C1C2 positions. MEP recordings were made in the abductor hallucis (AH) and tibialis anterior (TA) with needle electrodes.
  
  
  RESULTS
  Reproducible MEPs were obtained throughout the operation in all 20 cases, with up to 80 mA per stimulator. Before insertion of pedicle screws, mean MEP amplitudes (SD) obtained were 85 (19) and 21.7 (10.8) mV for AH and TA, respectively, using desflurane. With TIVA, amplitudes were 56.7 (28.4) and 59.1 (24.5) mV, respectively. Both muscle MEP amplitudes were significantly different using different anesthetic regimens (P < 0.05 for all). AH MEP amplitudes obtained with desflurane were significantly larger than TA amplitudes (P < 0.0001). No complications were reported intraoperatively and postoperatively.
  
  
  CONCLUSIONS
  This is the first study comparing the use of desflurane and TIVA showing that both anesthetic regimens allowed successful intraoperative monitoring useage throughout the procedures. For MEP recording, the AH was the preferred muscle with a desflurane anesthetic regimen.
authors.affiliation: Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Singapore. gnrlyl@sgh.com.sg
authors.forename: Yew-Long
authors.initials: YL
authors.lastname: Lo
authors.forename: Yang-Fang
authors.initials: YF
authors.lastname: Dan
authors.forename: Y E
authors.initials: YE
authors.lastname: Tan
authors.forename: Siti
authors.initials: S
authors.lastname: Nurjannah
authors.forename: Seang-Beng
authors.initials: SB
authors.lastname: Tan
authors.forename: Chong-Tein
authors.initials: CT
authors.lastname: Tan
authors.forename: Sitaram
authors.initials: S
authors.lastname: Raman
mesh_terms: D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D000077335:Desflurane; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives*; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D009609:Nitrous Oxide; D015742:Propofol; D011446:Prospective Studies; D012600:Scoliosis / Q000601:surgery*; D050781:Transcranial Magnetic Stimulation
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D000077335:Desflurane; D007530:Isoflurane; D009609:Nitrous Oxide; D015742:Propofol