Introduction

• Background: At the core of general anesthesia lies the critical objective of ensuring patient comfort while preventing awareness, not only to alleviate psychological distress but also to shield the anesthesiologist from potential legal repercussions⁽¹⁾. The consequence of inadequate sedation is the potential postoperative recollection of pain and sounds, underscoring the indispensable role of the Bispectral Index (BIS) in monitoring sedation depth through EEG signals, translated into an objective numerical value.⁽²⁾ Maintaining BIS values within the 40 to 60 range is imperative to guarantee optimal anesthesia, mitigate awareness, and diminish the likelihood of patient distress and legal entanglements for the anesthesiologist^(3,4). This significance is particularly accentuated in the intricate landscape of extensive neurosurgical brain and spine procedures.

1. Whitlock EL, Rodebaugh TL, Hassett AL, et al. Psychological sequelae of surgery in a prospective cohort of patients from three intraoperative awareness prevention trials. Anesth Analg. 2015;120(01):87–95.
2. Mashom, G., & Avidan, M. (2015). Intraoperative awareness: Controversies and Non-controversies. BJA, 115, 120-126.
3. Sinha P, Koshy T. Monitoring devices for measuring the depth of anesthesia - an overview. Indian J Anaesth. 2007;51(05):365–365.
4. Avidan MS, Zhang L, Burnside BA, et al. Anesthesia awareness and the bispectral index. N Engl J Med. 2008;358(11):1097–1108.
5. Akavipat P, Hungsawanich N, Jansin R. Alternative placement of bispectral index electrode for monitoring depth of anesthesia during neurosurgery. Acta Med Okayama. 2014;68(03):151–155.
6. Pandin, P., Van Cutsem, N., Tuna, T., & D’hollander, A. (2006). Bispectral Index Is a Topographically Dependent Variable in Patients Receiving Propofol Anaesthesia. British Journal of Anaesthesia, 97, 676-680. https://doi.org/10.1093/bja/ael523.
7. Konul Hajiyeva, Basak Ceyda Meco, Cigdem Yildirim Guclu, Dilek Yorukoglu, Beyza Doganay, Mehmet Oral. (2021). Comparison of Nasal and Frontal BIS Monitoring in Neurosurgery: Does the Site of Sensor Placement Affect the BIS Values? International Journal of Clinical Medicine, 12, 108-114. https://www.scirp.org/journal/ijcm ISSN Online: 2158-2882, ISSN Print: 2158-284X, DOI: 10.4236/ijcm.2021.123012 Mar. 22, 2021. 108 International Journal of Clinical Medicine.
8. 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(02):135–142.
9. Domino KB, Posner KL, Caplan RA, Cheney FW. Awareness during anesthesia: a closed claims analysis. Anesthesiology. 1999;90(04):1053–1061.
10. Lawrence Litt, Chapter 45, 290. Electroencephalography and Cerebral Function Monitoring, Essentials of Neuroanaesthesia and Neurointensive care. Arun K. Gupta, Adrian W. Gelb.
11. Roscow Cand Manberg P J: Bispectral Index Monitoring. Anesthesiol Clin North America. 2001;19:947-966, xi.
12. Medical Advisory Secretariat. (2004). Bispectral Index Monitor: An Evidence-Based Analysis. Ontario Health Technology Assessment Series, 4, 1-70.
13. Kelly S D: Monitoring Consciousness during Anaesthesia and Sedation: A Clinician’s guide to the Bispectral Index, Boston, Aspect Medical Systems, 2005, p. 2-2.
14. Lee, S. et al. (2004). Comparison of Bispectral Index Scores from the Standard Frontal Sensor Position with Those from an Alternative Mandibular Position. Anesthesia & Analgesia, 98, 1773-1775.
15. Dahaba, A. et al. (2006). BIS-Vista™ Occipital Montage in Patients Undergoing Neurosurgical Procedures during Propofol-Remifentanil Anesthesia. British Journal of Anaesthesia, 97, 676-680.
16. Sinha P K. Suneel P R, Unnikrishnan K P, Smita V, and Rathod R C: An alternative site for entropy sensor placement, Anaesth Analg. 2006;102:1291.
17. Shiraishi, T., Uchino, H., Sagara, T., & Ishii, N. (2004). A Comparison of Frontal and Occipital Bispectral Index. Anesthesia & Analgesia, 98, 1773-1775. https://doi.org/10.1213/01.ANE.0000121344.69058.09.
18. Jitendra K. Dubey, Nitesh Goel, Rajiv Chawla, Manish Gupta, Manoj Bhardwaj. (2022). Supralabial Site: An Alternative Site for Bispectral Index Monitoring: A Cross-sectional Study, J Neuroanaesthesiol Crit Care, 9, 149–154.
19. Ekman A, Lindholm ML, Lennmarken C, Sandin R. Reduction in the incidence of awareness using BIS monitoring. Acta Anaesthesiol Scand Journal. 2004;48(01):20–26.
20. Manberg P J: BIS monitoring requires proper electrode placement for optimum performance. Anesth Analg. 2003;97:1206: author reply.

Dr Roshni Cheema

MBBS, KEMH Mumbai; MD Anesthesiology BHIMS, Mumbai