title: Vagal sensory evoked potentials disappear under the neuromuscular block - an experimental study.
abstract: BACKGROUND
  Transcutaneous vagal nerve stimulation is a promising treatment modality in patients suffering mood disorders and chronic pain, however, the mechanisms are still to be elucidated. A recently developed technique of EEG responses to electrical stimulation of the inner side of the tragus suggests that these responses are far field potentials, generated in the vagal system - Vagal Sensory Evoked Potentials (VSEP).
  
  
  OBJECTIVE
  To reproduce the VSEP technique free from myogenic artifacts.
  
  
  METHODS
  Fourteen ASA I-II patients scheduled for elective surgery in standardized Total Intravenous Anesthesia (TIVA) were enrolled. Transcutaneous electrical stimulation was applied to the inner side of the right tragus. Averaged EEG responses were recorded from the electrode positions C4-F4 and T4-O2 before and after induction of TIVA, during the maximal effect of the non-depolarizing muscle relaxing agent, cis-atracurium (C-AR) and after recovery from C-AR under TIVA.
  
  
  RESULTS
  Typical response curves with P1, N1 and P2 peaks could be reproduced in all patients before and after anesthesia induction. The response curves disappeared during the C-AR action and re-appeared after recovery from C-AR under TIVA.
  
  
  CONCLUSIONS
  The disappearance of the scalp responses to electrical tragus stimulation under the neuromuscular block suggests a muscular origin of these potentials.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Medicine of Greifswald, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Leutzow
authors.forename: Jörn
authors.initials: J
authors.lastname: Lange
authors.forename: Andreas
authors.initials: A
authors.lastname: Gibb
authors.forename: Henry
authors.initials: H
authors.lastname: Schroeder
authors.forename: Andreas
authors.initials: A
authors.lastname: Nowak
authors.forename: Michael
authors.initials: M
authors.lastname: Wendt
authors.forename: Taras I
authors.initials: TI
authors.lastname: Usichenko
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000494:pharmacology; D019148:Neuromuscular Blockade; D004561:Transcutaneous Electric Nerve Stimulation; D055536:Vagus Nerve Stimulation
chemical_list: D009465:Neuromuscular Agents
keywords: Evoked potentials; Neuromuscular block; Transcutaneous vagal nerve stimulation