title: Effects of propofol, sevoflurane, remifentanil, and (S)-ketamine in subanesthetic concentrations on visceral and somatosensory pain-evoked potentials.
abstract: BACKGROUND
  Although electroencephalographic parameters and auditory evoked potentials (AEP) reflect the hypnotic component of anesthesia, there is currently no specific and mechanism-based monitoring tool for anesthesia-induced blockade of nociceptive inputs. The aim of this study was to assess visceral pain-evoked potentials (VPEP) and contact heat-evoked potentials (CHEP) as electroencephalographic indicators of drug-induced changes of visceral and somatosensory pain. Additionally, AEP and electroencephalographic permutation entropy were used to evaluate sedative components of the applied drugs.
  
  
  METHODS
  In a study enrolling 60 volunteers, VPEP, CHEP (amplitude N2-P1), and AEP (latency Nb, amplitude Pa-Nb) were recorded without drug application and at two subanesthetic concentration levels of propofol, sevoflurane, remifentanil, or (s)-ketamine. Drug-induced changes of evoked potentials were analyzed. VPEP were generated by electric stimuli using bipolar electrodes positioned in the distal esophagus. For CHEP, heat pulses were given to the medial aspect of the right forearm using a CHEP stimulator. In addition to AEP, electroencephalographic permutation entropy was used to indicate level of sedation.
  
  
  RESULTS
  With increasing concentrations of propofol, sevoflurane, remifentanil, and (s)-ketamine, VPEP and CHEP N2-P1 amplitudes decreased. AEP and electroencephalographic permutation entropy showed neither clinically relevant nor statistically significant suppression of cortical activity during drug application.
  
  
  CONCLUSIONS
  Decreasing VPEP and CHEP amplitudes under subanesthetic concentrations of propofol, sevoflurane, remifentanil, and (s)-ketamine indicate suppressive drug effects. These effects seem to be specific for analgesia.
authors.affiliation: Department of Anesthesiology, Helios Clinic Wuppertal, Witten/Herdecke University, Wuppertal, Germany.
authors.forename: Gisela
authors.initials: G
authors.lastname: Untergehrer
authors.forename: Denis
authors.initials: D
authors.lastname: Jordan
authors.forename: Sebastian
authors.initials: S
authors.lastname: Eyl
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schneider
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000778:Anesthetics, Dissociative / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects; D019277:Entropy; D005071:Evoked Potentials / Q000187:drug effects*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D006801:Humans; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D010880:Piperidines / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D000077208:Remifentanil; D000077149:Sevoflurane; D059265:Visceral Pain / Q000503:physiopathology*
chemical_list: D000701:Analgesics, Opioid; D000778:Anesthetics, Dissociative; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D010880:Piperidines; D000077149:Sevoflurane; D007649:Ketamine; D000077208:Remifentanil; D015742:Propofol