title: Accuracy of the composite variability index as a measure of the balance between nociception and antinociception during anesthesia.
abstract: BACKGROUND
  The Composite Variability Index (CVI), derived from the electroencephalogram, was developed to assess the antinociception-nociception balance, whereas the Bispectral Index (BIS) was developed to assess the hypnotic state during anesthesia. We studied the relationships between these indices, level of hypnosis (BIS level), and antinociception (predicted remifentanil effect-site concentrations, CeREMI) before and after stimulation. Also, we measured their association with movement in response to a noxious stimulus.
  
  
  METHODS
  We randomized 120 patients to one of 12 groups targeting different hypnotic levels (BIS 70, 50, and 30) and various CeREMI (0, 2, 4, or 6 ng/mL). At pseudo-steady state, baseline values were observed, and a series of stimuli were applied. Changes in BIS, CVI, heart rate (HR), and mean arterial blood pressure (MAP) between baseline and response period were analyzed in relation to level of hypnosis, antinociception, and somatic response to the stimuli.
  
  
  RESULTS
  CVI and BIS more accurately correlate with somatic response to an Observer Assessment of Alertness and Sedation-noxious stimulation than HR, MAP, CeREMI, and propofol effect-site concentration (Tukey post hoc tests P < 0.01). Change in CVI is more adequate to monitor response to stimulation than changes in BIS, HR, or MAP (as described by the Mathews Correlation Coefficient with significance level set at P < 0.001). In contrast, none of the candidate analgesic state indices was uniquely related to a specific opioid concentration and is extensively influenced by the hypnotic state as measured by BIS.
  
  
  CONCLUSIONS
  CVI appears to correlate with somatic responses to noxious stimuli. However, unstimulated CVI depends more on hypnotic drug effect than on opioid concentration.
authors.affiliation: From the Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Demed, Temse, Belgium; Respiratory Monitoring Solutions, Covidien, Boulder, Colorado; and Department of Anesthesia, University of Ghent, Gent, Belgium.
authors.forename: Marco M
authors.initials: MM
authors.lastname: Sahinovic
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Eleveld
authors.forename: Alain F
authors.initials: AF
authors.lastname: Kalmar
authors.forename: Eleonora H
authors.initials: EH
authors.lastname: Heeremans
authors.forename: Tom
authors.initials: T
authors.lastname: De Smet
authors.forename: Chandran V
authors.initials: CV
authors.lastname: Seshagiri
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Absalom
authors.forename: Hugo E M
authors.initials: HEM
authors.lastname: Vereecke
authors.forename: Michel M R F
authors.initials: MMRF
authors.lastname: Struys
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D062186:Arterial Pressure / Q000187:drug effects; D001288:Attention / Q000187:drug effects; D003243:Consciousness / Q000187:drug effects*; D056805:Consciousness Monitors; D004569:Electroencephalography / Q000295:instrumentation; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage*; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D009426:Netherlands; D059225:Nociception / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects; D010880:Piperidines / Q000008:administration & dosage*; D011237:Predictive Value of Tests; D015742:Propofol / Q000008:administration & dosage; D000077208:Remifentanil; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol