Influence of Isoflurane on Myogenic Motor Evoked Potentials to Single and Multiple Transcranial Stimuli during Nitrous Oxide/Opioid Anesthesia

Influence of Isoflurane on Myogenic Motor Evoked Potentials to Single and Multiple Transcranial... AbstractOBJECTIVE:Transcranial motor evoked potentials (tc-MEPs) are used to monitor the spinal cord intraoperatively. Volatile anesthetics considerably depress amplitudes of tc-MEPs. This study was undertaken to determine whether multipulse stimulation might overcome this depressant effect.METHODS:In 10 patients undergoing spinal surgery, incremental doses of isoflurane were added to a nitrous oxide/opioid anesthetic regimen and maintained constant at 0.2, 0.4, and 0.6% end tidal for at least 15 minutes. tc-MEP responses to single-pulse and trains of three and five (interstimulus interval, 2 ms) transcranial electrical stimuli were recorded from the tibialis anterior muscles.RESULTS:Before the addition of isoflurane, tc-MEPs were recordable in all patients, even with single-pulse stimuli (median amplitude, 428 μV). With 0.2% end-tidal isoflurane, tc-MEPs were recordable in eight patients with single-pulse stimulation and in all patients with three and five successive stimuli. At 0.4% isoflurane, responses were recordable in only one patient using single-pulse stimuli and in all patients using three and five stimuli. With 0.6% isoflurane, tc-MEPs to trains of three and five stimuli were recordable in all patients except one. The amplitude of the responses obtained with 0.2, 0.4, and 0.6% end-tidal isoflurane was significantly smaller than that of control responses (P < 0.05).CONCLUSION:These data suggest that despite the powerful depressant effects of isoflurane on myogenic motor responses, tc-MEP monitoring during isoflurane anesthesia may be feasible, provided that multipulse stimulation paradigms are used and the concentration of isoflurane does not exceed 1 minimal anesthetic concentration unit. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Neurosurgery Oxford University Press

Influence of Isoflurane on Myogenic Motor Evoked Potentials to Single and Multiple Transcranial Stimuli during Nitrous Oxide/Opioid Anesthesia

Influence of Isoflurane on Myogenic Motor Evoked Potentials to Single and Multiple Transcranial Stimuli during Nitrous Oxide/Opioid Anesthesia

TECHNIQUE EVALUATION Influence of Isoflurane on Myogenic Motor Evoked Potentials to Single and Multiple Transcranial Stimuli during Nitrous Oxide/Opioid Anesthesia Leon H. Ubags, M.D., Cor J. Kalkman, M.D., Ph.D., Henk D. Been, M.D., Ph.D. Departments of Anesthesiology (LH U , CJK) and Orthopaedics (H D B), Academ ic Hospital, University of Amsterdam, The Netherlands O BJECTIVE: Transcranial motor evoked potentials (tc-MEPs) are used to monitor the spinal cord intraoperatively. Volatile anesthetics considerably depress amplitudes of tc-MEPs. This study was undertaken to determine whether multipulse stimulation might overcome this depressant effect. M ETH O D S: In 10 patients undergoing spinal surgery, incremental doses of isoflurane were added to a nitrous oxide/opioid anesthetic regimen and maintained constant at 0.2, 0.4, and 0 .6 % end tidal for at least 15 minutes. tc-MEP responses to single-pulse and trains of three and five (interstimulus interval, 2 ms) transcranial electrical stimuli were recorded from the tibialis anterior muscles. RESULTS: Before the addition of isoflurane, tc-MEPs were recordable in all patients, even with single-pulse stimuli (median amplitude, 428 /mV). With 0 .2 % end-tidal isoflurane, tc-MEPs were recordable in eight patients with single-pulse stimulation and in all patients with three and five successive stimuli. At 0 .4 % isoflurane, responses were recordable in only one patient using single-pulse stimuli and in all patients using three and five stimuli. With 0.6% isoflurane, tc-MEPs to trains of three and five stimuli were recordable in all patients except one. The amplitude of the responses obtained with 0.2, 0.4, and 0 .6 % end-tidal isoflurane was significantly smaller than that of control responses (P < 0.05). C O N C L U S IO N : These data suggest that despite the powerful depressant effects of isoflurane on myogenic motor responses, tc-MEP monitoring during isoflurane anesthesia may be feasible, provided that...
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Publisher
Oxford University Press
Copyright
© Published by Oxford University Press.
ISSN
0148-396X
eISSN
1524-4040
D.O.I.
10.1097/00006123-199807000-00058
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Abstract

AbstractOBJECTIVE:Transcranial motor evoked potentials (tc-MEPs) are used to monitor the spinal cord intraoperatively. Volatile anesthetics considerably depress amplitudes of tc-MEPs. This study was undertaken to determine whether multipulse stimulation might overcome this depressant effect.METHODS:In 10 patients undergoing spinal surgery, incremental doses of isoflurane were added to a nitrous oxide/opioid anesthetic regimen and maintained constant at 0.2, 0.4, and 0.6% end tidal for at least 15 minutes. tc-MEP responses to single-pulse and trains of three and five (interstimulus interval, 2 ms) transcranial electrical stimuli were recorded from the tibialis anterior muscles.RESULTS:Before the addition of isoflurane, tc-MEPs were recordable in all patients, even with single-pulse stimuli (median amplitude, 428 μV). With 0.2% end-tidal isoflurane, tc-MEPs were recordable in eight patients with single-pulse stimulation and in all patients with three and five successive stimuli. At 0.4% isoflurane, responses were recordable in only one patient using single-pulse stimuli and in all patients using three and five stimuli. With 0.6% isoflurane, tc-MEPs to trains of three and five stimuli were recordable in all patients except one. The amplitude of the responses obtained with 0.2, 0.4, and 0.6% end-tidal isoflurane was significantly smaller than that of control responses (P < 0.05).CONCLUSION:These data suggest that despite the powerful depressant effects of isoflurane on myogenic motor responses, tc-MEP monitoring during isoflurane anesthesia may be feasible, provided that multipulse stimulation paradigms are used and the concentration of isoflurane does not exceed 1 minimal anesthetic concentration unit.

Journal

NeurosurgeryOxford University Press

Published: Jul 1, 1998

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