Advertisement

The effect of addition of nitrous oxide to a sevoflurane anesthetic on BIS, PSI, and entropy

  • Roy G. Soto
  • Robert A. Smith
  • Amy L. Zaccaria
  • Rafael V. Miguel
Article

Abstract

Objective. N2O is a commonly used anesthetic that has amnestic and analgesic properties. Recently, devices that estimate depth of consciousness have been introduced in an attempt to better titrate anesthesia, however the effect of N2O on these monitors is unclear. Methods. General anesthesia was induced and titrated to maintain normal blood pressure and pulse in healthy adults. Data were collected in three 10 minute intervals (Sevo, Sevo + N2O, Sevo). In Phase A, sevoflurane concentration was held constant during the N2O trial in 60 subjects monitored with either BIS, PSI, or Entropy. In Phase B, sevoflurane concentration was reduced as N2O was added, maintaining a constant overall “MAC” in 20 subjects monitored concurrently with BIS and Entropy. Sample size for both phases was designed to detect a 10 unit change in measure of processed EEG with alpha = .05 and statistical power = .80. Results. In Phase A, supplementing sevoflurane with > 65% N2O increased MAC from 1.3 ± 0.05 to 2.2 ± 0.10, but did not significantly alter BIS nor PSI (p-value for differential MAC is < 0.05). Entropy, however, dropped significantly, with a change in state entropy (SE) from 31.1 ± 7.3 to 18.9 ± 3.7 and a corresponding rise when N2O was discontinued. In Phase B, supplementing sevoflurane with > 65% N2O with a concomitant reduction in sevoflurane resulted in an increase in both BIS (from 34 ± 5 to 53.9 ± 11.5) and SE (from 32 ± 8.2 to 55.4 ± 21.3). Conclusion. Supplementing sevoflurane with > 65% N2O did not result in a significant change in either BIS or PSI when sevoflurane concentration was kept constant. Entropy, however, significantly decreased as anesthetic depth increased. When sevoflurane concentration was reduced during N2O administration, both BIS and Entropy rose despite maintenance of anesthetic depth, indicating a variable concentration effect between volatiles and N2O.

Keywords

Processed EEG consciousness sedation 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Johansen J, Sebel P. Development and clinical application of electroencephalographic bispectrum monitoring. Anesthesiology 2000; 93: 1335–1344.CrossRefGoogle Scholar
  2. 2.
    Prichep L, Gugino L, John E, Chabot R, Howard B, Merkin H, Tom M, Wolter S, Rausch L, Kox W. The Patient State Index as an indicator of the level of hypnosis under general anaesthesia. Br J Anaesth 2004; 92: 393–399.PubMedCrossRefGoogle Scholar
  3. 3.
    Vakkuri A, Yli-Hankala A, Talja P, Mustola S, et al. Time-frequency balanced spectral entropy as a measure of anesthetic drug effect in central nervous system during sevoflurane, propofol, and thiopental anesthesia. Acta Anaesth Scand 2004; 48: 145–153.PubMedCrossRefGoogle Scholar
  4. 4.
    Eger EI II, Saidman LJ, Brandstater B. Minimum alveolar anesthetic concentration: A standard of anesthetic potency. Anesthesiology 1965; 26: 756–763.PubMedCrossRefGoogle Scholar
  5. 5.
    Rampil IJ, Mason P, Singh H. Anesthetic potency (MAC) is independent of forebrain structures in the rat. Anesthesiology 1993; 78: 707–712.PubMedCrossRefGoogle Scholar
  6. 6.
    Sebel PS, Lang E, Rampil IJ, White PF, Cork R, Jopling M, Smith NT, Glass PSA, Manberg P. A Multicenter Study of Bispectral Electroencephalogram Analysis for Monitoring Anesthetic Effect. Anesthesia & Analgesia 1997; 84: 891–899.CrossRefGoogle Scholar
  7. 7.
    Saidman L, Eger E. Effect of nitrous oxide and of narcotic premedication on the alveolar concentration of halothane required for anesthesia. Anesthesiology. 1964; 25: 302–306.PubMedCrossRefGoogle Scholar
  8. 8.
    Torri G, Damia G, Fabiani M. Effect of nitrous oxide on the anaesthetic requirement of enflurane. Br J Anaesth 1974; 46: 468–472.PubMedCrossRefGoogle Scholar
  9. 9.
    Stevens W, Dolan W, Gibbons R, White A, Eger E, Miller R, De Jong R, Elashoff .: Minimum alveolar concentrations (MAC) of isoflurane with and without nitrous oxide in patients of various ages. Anesthesiology 1975; 42: 197–200.PubMedGoogle Scholar
  10. 10.
    Rampil I, Kim J, Lenhardt R, Negishi C, Sessler D. Bispectral EEG index during nitrous oxide administration. Anesthesiology 1998; 89: 671–677.PubMedCrossRefGoogle Scholar
  11. 11.
    Barr G, Jakobsson J, Owall A, Anderson R. Nitrous oxide does not alter bispectral index: Study with nitrous oxide as sole agent and as an adjunct to IV. anaesthesia. Br J Anaesth 1999; 82: 827–830.PubMedGoogle Scholar
  12. 12.
    Anderson R, Jakobsson J. Entropy of EEG during anaesthetic induction: A comparative study with propofol or nitrous oxide as sole agent. Br J Anaesth 2004; 92: 167–170.PubMedCrossRefGoogle Scholar
  13. 13.
    Johansen J, Sebel P. Development and clinical application of electroencephalographic bispectrum monitoring. Anesthesiology 2000; 93: 1335–1344.CrossRefGoogle Scholar
  14. 14.
    Vanluchene A, Vereecke H, Thas O, Mortier E, Shafer S, Struys M. Spectral entropy as an electroencephalographic measure of anesthetic drug effect: A comparison with bispectral index and processed midlatency auditory evoked response. Anesthesiology 2004; 101: 34–42.PubMedCrossRefGoogle Scholar
  15. 15.
    Röpcke H, Lier H, Hoeft A, Schwilden H. Isoflurane, nitrous oxide, and fentanyl pharmacodynamic interactions in surgical patients as measured by effects on median power frequency. J Clin Anesth 1999; 11: 555–562.PubMedCrossRefGoogle Scholar
  16. 16.
    Röpcke H, Schwilden H, Interaction of isoflurane and nitrous oxide combinations similar for median electroencephalographic frequency and clinical anesthesia. Anesthesiology 1996; 84: 782–788.PubMedCrossRefGoogle Scholar
  17. 17.
    Röpcke H, Wirz S, Bouillon T, Bruhn J, Hoeft A. Pharmacodynamic interaction of nitrous oxide with sevoflurane, desflurane, isoflurane, and enflurane in surgical patients: Measurements by effects on EEG median power frequency. Eur J Anesth 2001; 18: 440–449.CrossRefGoogle Scholar
  18. 18.
    Bruhn J, Ropcke H, Hoeft A. Approximate entropy as an electroencephalographic measure of anesthetic drug effect during desflurane anesthesia. Anesthesiology 2000; 92: 715–726.PubMedCrossRefGoogle Scholar
  19. 19.
    Rampil I, Laster M. No correlation between quantitative electroencephalographic measurements and movement response to noxious stimuli during isoflurane anesthesia in rats. Anesthesiology 1992; 77: 920–925.PubMedCrossRefGoogle Scholar
  20. 20.
    Hans P, Dewandre P, Brichant J, Bonhomme V. Effects of nitrous oxide on spectral entropy of the EEG during surgery under balanced anaesthesia with sufentanil and sevoflurane. Acta Anaesthesiol Belg 2005; 56: 37–43.PubMedGoogle Scholar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Roy G. Soto
    • 1
  • Robert A. Smith
    • 2
  • Amy L. Zaccaria
    • 3
  • Rafael V. Miguel
    • 4
  1. 1.Department of AnesthesiologyUniversity at Stony BrookStony BrookUSA
  2. 2.Division of Lung DiseasesNational Heart, Lung and Blood Institute, National Institutes of HealthBethesdaUSA
  3. 3.College of MedicineUniversity of South FloridaTampaUSA
  4. 4.Department of AnesthesiologyUniversity of South FloridaTampaUSA

Personalised recommendations