Anesthesia depth monitoring using alternative placement of entropy sensors: a prospective study

  • David I. Vachnadze
  • Boris A. Akselrod
  • Denis A. Guskov
  • Alevtina V. Goncharova
Original Research


Spectral entropy is based on analysis of variations in electroencephalography and frontal electromyography, and is a safe and reliable method for anesthesia depth monitoring. However, standard frontal positioning of entropy electrodes in patients undergoing cardiac surgery is sometimes challenging. The present study aimed to compare standard entropy sensor placement with an alternative (infraorbital) site. This prospective study included 20 patients who underwent cardiovascular surgery at the authors’ center. Monitoring was performed with standard and alternative entropy electrode positions from patient admission to surgery to transfer to the intensive care unit. Data were recorded every 15 s; all data were analyzed and compared using Bland–Altman, scatter plot with Pearson correlation coefficient, and sensitivity/specificity analyses. Overall, 20,784 pairs of response entropy (RE) and state entropy (SE) indexes were collected. Bland–Altman analysis revealed a mean difference in RE of 0.37 (95% LOA − 7.09, 7.88) and SE 0.69 (95% LOA − 5.95, 7.31); with 3.46% (720/20,784) RE and 3.40% (706/10,790) SE values lying outside of the limits of agreement. Correlation analysis revealed strong positive correlation in both cases: RE, r = 0.983, p < 0.05; SE, r = 0.984; p < 0.05. Sensitivity/specificity analysis revealed 98.1% sensitivity, 93.3% specificity and 97.1% test efficiency for RE, and 99.2%, 95.1% and 98.5% for SE, respectively. Infraorbital entropy sensor placement in patients undergoing cardiovascular surgery is reliable and effective. The strong positive correlation between the two methods of registration enables alternative entropy measurement when frontal placement is not possible.


Entropy Spectral entropy Anesthesia depth Neuromonitoring 



This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. 1.
    Arutyunyan OM, Yavorovsky AG, Seleznev MN, Guleshov VA, Bunyatyan AA. Entropy monitoring of anesthetic depth at cardiac surgery. Vestnik Anestesiologii I Reanimatologii. 2011;6:17–23.Google Scholar
  2. 2.
    Chhabra A, Subramaniam R, Srivastava A, Prabhakar H, Kalaivani M, Paranjape S. Spectral entropy monitoring for adults and children undergoing general anaesthesia. Cochrane Database Syst Rev. 2016;3:CD010135.Google Scholar
  3. 3.
    Dahaba AA, Xue JX, Zhao GG, et al. BIS-vista occipital montage in patients undergoing neurosurgical procedures during propofol remifentanil anesthesia. Anesthesiology. 2010;112:645–51.CrossRefGoogle Scholar
  4. 4.
    Hall JD, Lockwood GG. Bispectral index: comparison of two montages. Br J Anaesth. 1998;80:342–4.CrossRefGoogle Scholar
  5. 5.
    Nelson P, Nelson JA, Chen AJ, Kofke WA. An alternative position for the BIS-Vista montage in frontal approach neurosurgical cases. J Neurosurg Anesthesiol. 2013;25:135–42.CrossRefGoogle Scholar
  6. 6.
    Viertiö-Oja H, Maja V, Särkelä M, Talja P, Tenkanen N, Tolvanen-Laakso H, et al. Description of the entropy algorithm as applied in the Datex-Ohmeda S/5 entropy module. Acta Anaesthesiol Scand. 2004;48:154–61.CrossRefGoogle Scholar
  7. 7.
    Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;1:307–10.CrossRefGoogle Scholar
  8. 8.
    Jiahai M. Spectral entropy monitoring reduces anesthetic dosage for patients undergoing off-pump coronary artery bypass graft surgery. J Cardiothorac Vasc Anesth. 2012;26:818–21.CrossRefGoogle Scholar
  9. 9.
    Shepherd J, Jones J, Frampton G, Bryant J, Baxter L, Cooper K. Clinical effectiveness and cost-effectiveness of depth of anaesthesia monitoring (E-Entropy, Bispectral Index and Narcotrend): a systematic review and economic evaluation. Health Technol Assess. 2013;17(34):1–264.CrossRefGoogle Scholar
  10. 10.
    Leon S. Awareness in cardiac anesthesia. Curr Opin Anesthesiol. 2010;23:103–8.CrossRefGoogle Scholar
  11. 11.
    Yu H, Wu D. Effects of different methods of general anesthesia on intraoperative awareness in surgical patients. Medicine (Baltimore). 2017;96(42):e6428.CrossRefGoogle Scholar
  12. 12.
    Messina AG, Wang M, Ward MJ, Wilker CC, Eggers M, Miller DB, et al. The effectiveness of anaesthetic interventions for prevention of wakefulness and awareness during and after surgery. Cochrane Database Syst Rev. 2008;3:803–8.Google Scholar
  13. 13.
    Shiraishi T, Uchino H, Sagara T, et al. A comparison of frontal and occipital bispectral index values obtained during neurosurgical procedures. Anesth Analg. 2004;98:1773–5.CrossRefGoogle Scholar
  14. 14.
    Singh S, Bansal S, Kumar G, Gupta I, Thakur JR. Entropy as an indicator to measure depth of anaesthesia for laryngeal mask airway (LMA) insertion during sevoflurane and propofol anaesthesia. J Clin Diagn Res. 2017;11(7):1–3.Google Scholar
  15. 15.
    Messina AG, Wang M, Ward MJ, Wilker CC, Smith BB, Vezina DP, Pace NL. Anaesthetic interventions for prevention of awareness during surgery. Cochrane Database Syst Rev. 2016;10.Google Scholar
  16. 16.
    Akavipat P, Hungsawanich N, Jansin R. Alternative placement of bispectral index electrode for monitoring depth of anesthesia during neurosurgery. Acta Med Okayama. 2014;68:151–5.Google Scholar
  17. 17.
    Lee SY, Kim YS, Lim BG, Kim H, Kong MH, Lee IO. Comparison of bispectral index scores from the standard frontal sensor position with those from an alternative mandibular position. Korean J Anesthesiol. 2014;66:267–73.CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.FSBSI «Petrovsky NRCS»MoscowRussia

Personalised recommendations