title: Identification of sensory blockade by somatosensory and pain-induced evoked potentials.
abstract: BACKGROUND
  To date, the anesthesia-induced blockade of nociceptive inputs is insufficiently reflected by commercially available electroencephalographic depth-of-anesthesia monitors. The aim of the current study was to evaluate the potential of somatosensory (SSEP) and intracutaneous pain evoked (iSEP) potentials during remifentanil and propofol anesthesia as electroencephalographic indicators of the nociceptive blockade.
  
  
  METHODS
  Ten healthy men were investigated in a double-blind crossover design during three sessions with remifentanil, propofol, and placebo administration. All dosages were increased in a step-by-step mode. SSEP and iSEP recordings were performed followed by subjective pain ratings and measurement of level of sedation (modified Observer's Assessment of Alertness and Sedation Scale). Changes from baseline in evoked potential components, pain ratings, and sedation scale were assessed by Bonferroni-Holms-corrected Wilcoxon tests.
  
  
  RESULTS
  Pain ratings were significantly reduced by remifentanil. Sedation scale was significantly reduced by propofol. Early SSEP components were not affected by medication. The amplitudes of the long latency SSEP components increased significantly with remifentanil, decreased with propofol, and did not change with placebo. The amplitudes of long latency components of the iSEP decreased significantly with both remifentanil and propofol and did not change with placebo.
  
  
  CONCLUSIONS
  Long latency components of the SSEP are differently affected by remifentanil and propofol administration. Further studies are needed to clarify whether they can serve as a specific indicator of the nociceptive blockade during anesthesia.
authors.affiliation: Department of Anesthesiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. guschmid@uke.uni-hamburg.de
authors.forename: Gunter N
authors.initials: GN
authors.lastname: Schmidt
authors.forename: Eckehard
authors.initials: E
authors.lastname: Scharein
authors.forename: Markus
authors.initials: M
authors.lastname: Siegel
authors.forename: Jakob
authors.initials: J
authors.lastname: Müller
authors.forename: Stefan
authors.initials: S
authors.lastname: Debener
authors.forename: Rainer
authors.initials: R
authors.lastname: Nitzschke
authors.forename: Andreas
authors.initials: A
authors.lastname: Engel
authors.forename: Petra
authors.initials: P
authors.lastname: Bischoff
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000494:pharmacology*; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010880:Piperidines / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D000077208:Remifentanil
chemical_list: D000701:Analgesics, Opioid; D006993:Hypnotics and Sedatives; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol