This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by van Dongen, E. P. Articles by Boezeman, E. H. Search for Related Content PubMed PubMed Citation Articles by van Dongen, E. P. Articles by Boezeman, E. H.

---

CARDIOVASCULAR ANESTHESIA

Within-Patient Variability of Myogenic Motor-Evoked Potentials to Multipulse Transcranial Electrical Stimulation During Two Levels of Partial Neuromuscular Blockade in Aortic Surgery

Eric P. van Dongen, MD^*, Huub T. ter Beek, MD^*, Marc A. Schepens, MD, PhD, Wim J. Morshuis, MD, PhD, Han J. Langemeijer, MD, PhD^*, Anthonius de Boer, MD, PhD, and Eduard H. Boezeman, MD, PhD

Departments of *Anesthesiology and Intensive Care, Clinical Neurophysiology, Cardiothoracic Surgery, St. Antonius Hospital, Nieuwegein; and Department of Pharmacoepidemiology and Pharmacotherapy, Faculty of Pharmacy, University of Utrecht, Utrecht, The Netherlands

Address correspondence and reprint requests to Eric P. van Dongen, Department of Anesthesiology and Intensive Care, St. Antonius Hospital, Koekoekslaan 1, 3435 CM Nieuwegein, The Netherlands.

Intraoperative recording of myogenic motor responses evoked by transcranial electrical stimulation (tcMEPs) is a method of assessing the integrity of the motor pathways during aortic surgery. To identify conditions for optimal spinal cord monitoring, we investigated the effects of manipulating the level of neuromuscular blockade (T1 response of the train-of-four (TOF) stimulation 5%–15% versus T1 response 45%–55% of baseline), as well as the number of transcranial pulses (two versus six stimuli) on the within-patient variability and amplitude of tcMEPs. Ten patients (30–76 yr) scheduled to undergo surgery on the thoracic and thoracoabdominal aorta were studied. After achieving a stable anesthetic state and before surgery, 10 tcMEPs were recorded from the right extensor digitorum communis muscle and the right tibialis anterior muscle in response to two-pulse and six-pulse transcranial electrical stimulation with an interstimulus interval of 2 ms during two levels of neuromuscular blockade. The right thenar eminence was used for recording the level of relaxation. The tcMEP amplitude using the six-pulse paradigm was larger (P < 0.01; leg and arm) compared with the amplitude evoked by two-pulse stimulation during both levels of relaxation. The within-patient variability, expressed as median coefficient of variation, was less when six-pulse stimulation was used. At a T1 response of 45%–55% of baseline, larger, less variable tcMEPs were recorded than at a T1 response of 5%–15%. Our results suggest that the best quality of tcMEP signals (tibialis anterior muscle) is obtained when the six-pulse paradigm is used with a stable level of muscle relaxation (the first twitch of the TOF—thenar eminence—at 45%–55% of baseline).

Implications: This study shows that six-pulse (rather than two-pulse) transcranial electrical stimulation during a stable anesthetic state and a stable neuromuscular blockade aimed at 45%–55% (rather than 5%–15%) of baseline provides reliable and recordable muscle responses sufficiently robust for spinal cord monitoring in aortic surgery.

This article has been cited by other articles:

				Y. Yamamoto, M. Kawaguchi, H. Hayashi, T. Horiuchi, S. Inoue, H. Nakase, T. Sakaki, and H. Furuya The Effects of the Neuromuscular Blockade Levels on Amplitudes of Posttetanic Motor-Evoked Potentials and Movement in Response to Transcranial Stimulation in Patients Receiving Propofol and Fentanyl Anesthesia Anesth. Analg., March 1, 2008; 106(3): 930 - 934. [Abstract] [Full Text] [PDF]

				E. C. Lases, M. A. Schepens, F. J. Haas, L. P. Aarts, H. T. ter Beek, E. P. van Dongen, H. P. Siegers, I. van der Tweel, and E. H. Boezeman Clinical prospective study of biochemical markers and evoked potentials for identifying adverse neurological outcome after thoracic and thoracoabdominal aortic aneurysm surgery Br. J. Anaesth., November 1, 2005; 95(5): 651 - 661. [Abstract] [Full Text] [PDF]