title: Influence of age on hypnotic requirement, bispectral index, and 95% spectral edge frequency associated with sedation induced by sevoflurane.
abstract: BACKGROUND
  Aging is associated with a reduction in anesthetic requirements. The effects of age on the electroencephalographic response to inhalational anesthesia have not been well documented. The objective of the present study was to determine the influence of age on hypnotic requirement and electroencephalographic derivatives such as bispectral index and 95% spectral edge frequency associated with sedation induced by sevoflurane.
  
  
  METHODS
  Ninety-six patients were randomly allocated into one of three age groups A, B, and C, ranging in age from 18-39 yr, 40-64 yr, and 65-85 yr, respectively. Patients in each group were sedated with sevoflurane at two predetermined concentrations ranging between 0.45% and 0.85%. The relationship between sevoflurane concentration and response to a verbal command, as well as the relationships between response and bispectral index and 95% spectral edge frequency, was determined.
  
  
  RESULTS
  Multiple regression analysis showed that end-tidal sevoflurane concentration and age significantly affected both bispectral index and 95% spectral edge frequency. ED50 values of sevoflurane concentration for loss of consciousness, defined as no response to verbal command, were different between groups A and C: 0.72 (95% confidence interval: 0.68-0.75) versus 0.59 (95% confidence interval: 0.56-0.62). However, the same effective values of bispectral index and 95% spectral edge frequency at this same clinical end point did not differ.
  
  
  CONCLUSIONS
  Increasing age reduced sevoflurane requirements to suppress responses to a verbal command but did not change bispectral index and 95% spectral edge frequency associated with this end point, and in a population with a wide age range, bispectral index would predict depth of sedation better than end-tidal sevoflurane concentration.
authors.affiliation: Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, Japan. tackatoh@hama-med.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Katoh
authors.forename: H
authors.initials: H
authors.lastname: Bito
authors.forename: S
authors.initials: S
authors.lastname: Sato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D016292:Procedural Sedation; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D011336:Probability; D011897:Random Allocation; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane