title: Etomidate activates epileptic high frequency oscillations.
abstract: OBJECTIVE
  The short acting anesthetic etomidate has been shown to provoke epileptic spikes and rarely seizures. Influence of etomidate on the occurrence of epileptic HFO (high frequency oscillations) however is unknown. An HFO inducing effect of etomidate would allow further validation of the substance as a provocation measure in presurgical evaluation as well as provide insights into the common mechanisms of HFO, spike and seizure generation.
  
  
  METHODS
  We retrospectively analyzed EEG data from four patients who underwent etomidate activation during invasive video-EEG monitoring with subdural strip electrodes. Spikes were manually selected in raw data, HFO in band pass filtered data (80-250Hz). Rate and spatial distribution of HFO and spikes in three segments were compared: immediately after etomidate administration, as well as during slow wave sleep and while awake.
  
  
  RESULTS
  Rates of HFO and spikes increased significantly after etomidate administration: Overall average rates of spikes were 9.7/min during sleep, 10/min while awake and 61.4/min after etomidate. Average HFO rates were 9.5/min during sleep, 8.3/min while awake and 24.4/min after etomidate (p<0.001, non-parametric ANOVA). Spatial distributions of HFO and spikes after administration of etomidate were consistent with the seizure onset zone (SOZ) and area of resection when available (SOZ: two patients; resection: one patient; no information: one patient). Except for spurious events, no additional HFO and spike foci were seen with activation.
  
  
  CONCLUSIONS
  Etomidate administration activates spikes and HFO. Spatial distributions do not extend beyond electrodes showing spikes and HFO without Etomidate and seem consistent with the epileptic network.
  
  
  CONCLUSIONS
  Etomidate activation is a safe procedure to provoke not only epileptic spikes but also HFO, which were shown to have a high specificity for the SOZ.
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany. Electronic address: stefan.rampp@uk-erlangen.de.
authors.forename: S
authors.initials: S
authors.lastname: Rampp
authors.affiliation: Department of Anesthesiology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Schmitt
authors.affiliation: Ruhr-Epileptology/Department of Neurology, University Hospital Knappschaftskrankenhaus Bochum, Bochum, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Heers
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schönherr
authors.affiliation: Department of Neurology, University Hospital Magdeburg, Magdeburg, Germany.
authors.forename: F C
authors.initials: FC
authors.lastname: Schmitt
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Hopfengärtner
authors.affiliation: Epilepsy Center, Department of Neurology, University Hospital Erlangen, Erlangen, Germany; Interdisciplinary Epilepsy Center, Neurological Clinic, University Hospital Giessen and Marburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Stefan
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000328:Adult; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000503:physiopathology* / Q000601:surgery; D005045:Etomidate / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012640:Seizures / Q000503:physiopathology* / Q000601:surgery; D012890:Sleep / Q000502:physiology; D013355:Subdural Space; D014851:Wakefulness
chemical_list: D018686:Anesthetics, Intravenous; D005045:Etomidate
keywords: Activation; Epilepsy; Etomidate; High frequency oscillations; Presurgical workup