Indian expert consensus on intra-operative consciousness monitoring using processed electroencephalogram-based indices: A Delphi-based approach

Abstract

Background and Aims:

In India, depth of anaesthesia monitoring with processed electroencephalogram (pEEG) is not routinely implemented. During volatile-based anaesthesia, end-tidal anaesthetic gas concentrations and age-adjusted minimum alveolar concentration values are widely accepted surrogates of anaesthetic depth. However, these measures do not directly reflect cortical activity, and no equivalent objective surrogate exists during total intravenous anaesthesia (TIVA). pEEG monitoring provides a direct assessment of cerebral activity and may support optimised anaesthetic titration, particularly in TIVA and other high-risk scenarios. The primary objective of this Delphi consensus was to develop expert-based, India-specific recommendations for the use of pEEG-based indices in intra-operative anaesthesia practice.

Methods:

A modified Delphi approach was employed with 15 anaesthesiology experts (13 Indian and 2 international). A Preferred Reporting Items for Systematic Reviews and Meta-analyses-based literature review, covering studies from 2016 to 2025, was conducted to develop 27 draft statements across 10 themes, including indications, target ranges, interpretation, and integration of pEEG with existing monitoring. Through structured iterative rounds involving a steering committee meeting (March 2025), and two rounds of advisory board (May 2025), the statements were revised, eliminated, or accepted based on high (≥80%), moderate (60–80%), or low (<60%) consensus.

Results:

Of the 27 initial statements, 19 achieved consensus and were included in the final statements. The statements spanned key clinical domains, including the need for depth of anaesthesia monitoring, role of pEEG-based indices, clinical benefits, indications based on anaesthetic techniques (TIVA and inhalational anaesthesia), patient characteristics, surgical context, and practical usage guidance, including target ranges and interpretation. Overall, the consensus supports the use of pEEG monitoring as an adjunct to optimise anaesthetic delivery, reduce drug consumption, and improve recovery profiles, particularly in high-risk and TIVA settings.

Conclusion:

This Delphi-based consensus provides a clinically relevant framework for integrating pEEG monitoring into anaesthesia practice in India. These recommendations aim to support personalised anaesthetic titration, enhance patient safety, and align peri-operative care with evolving global standards while accounting for local practice variability.

INTRODUCTION

The brain is the primary target of anaesthetic drugs. Yet, intra-operative monitoring in most Indian operating rooms continues to rely predominantly on haemodynamic surrogates and clinical observation.[1,2] While volatile-based anaesthesia is commonly guided by end-tidal anaesthetic gas (ETAG) concentrations and age-adjusted minimum alveolar concentration (MAC), which are well-validated indicators of anaesthetic depth, these measures do not directly reflect cortical activity. In contrast, during total intravenous anaesthesia (TIVA), no equivalent objective surrogate exists, making processed electroencephalography (pEEG) monitoring particularly relevant in such settings. p-EEG-based monitors such as the bispectral index (BIS), patient state index (PSI), electromyography (EMG), and state entropy (SE) provide a direct measure of cortical activity and have been increasingly recognised by international societies [European Society of Anaesthesiology (ESA) (2017),[3] American Society of Anesthesiologists (ASA),[4] the National Institute for Health and Care Excellence (NICE),[5] the Anesthesia Patient Safety Foundation (APSF),[6] and the World Federation of Societies of Anaesthesiologists (2018)[7]] as valuable adjuncts for titrating anaesthesia.[2,8] Meta-analyses data indicate that pEEG guidance can reduce the risk of intra-operative awareness by up to 64% compared to clinical signs alone, particularly in TIVA settings and high-risk cases.[9]

In India, the adoption of pEEG monitoring remains inconsistent and largely centre-dependent, influenced by factors such as cost, training gaps, and device availability.[10,11] The primary objective of this Delphi consensus was to develop expert-based statements for the use of pEEG monitoring in anaesthesia practice in India. A secondary objective was to contextualise these statements for Indian healthcare settings, including resource variability and implementation feasibility.

METHODS

Study design

A modified Delphi method was employed to systematically gather expert opinions and achieve consensus through iterative rounds of structured feedback and voting. This method was selected over other consensus techniques (e.g., nominal group technique or informal expert panels) due to its ability to systematically capture diverse expert opinions, maintain anonymity during voting, and iteratively refine statements based on collective feedback, making it particularly suitable for developing national-level clinical guidance in a heterogeneous healthcare landscape like India.

Panel selection

A total of 15 experts (13 from India and 2 international) in anaesthesiology were invited via email to join the advisory board, each being a recognised leader in the field (list of experts presented in Appendix 1). Experts were selected through purposive sampling based on pre-defined criteria, including academic leadership, clinical experience (15–40 years), and contributions to anaesthesiology through publications, fellowships, and national/international roles. The core panel included six experts (Appendix 1).

To minimise selection bias, the panel included specialists in cardiac anaesthesia, neuroanaesthesia, transplant anaesthesia, and critical care, with representation across geographies and a broad spectrum of Indian healthcare institutions—including government hospitals, private multi-speciality centres, medical colleges, and allied health institutes. No financial incentives influenced panel selection.

Two international experts were included to provide perspectives on established practices in high-resource settings and to facilitate comparison with Indian anaesthesia practice. Their contribution focussed on highlighting differences in the adoption and utilisation of pEEG monitoring (including BIS) between Western and Indian settings, and on identifying practices that may be adaptable to the Indian context. This helped ensure that the recommendations were both locally relevant and informed by global standards.

Consensus Statement generation

A comprehensive literature review was performed across PubMed, Embase (Elsevier), and Cochrane Library for the period from 1 January 2016 to 1 March 2025 using the keywords: ‘bispectral index’, ‘electroencephalogram’, ‘anaesthesia’, ‘depth’, ‘consciousness monitoring’, intraoperative awareness’, ‘total intravenous anaesthesia’, ‘postoperative cognitive decline’, and ‘delirium’. The screening and selection of retrieved articles adhered to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The PRISMA flowchart is presented in Figure 1.[12] Studies were included if they evaluated the use of pEEG monitoring in high-risk surgical populations or patients with comorbidities or in scenarios such as TIVA, titration of anaesthesia, haemodynamic instability, drug-related complications, neurological outcomes, quality of life, and determination of optimal BIS ranges using different anaesthetic agents and monitoring indices.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) flowchart for identification of studies

Consensus voting procedure

A three-step modified Delphi process was implemented to develop and refine the consensus statements. A virtual steering committee meeting was held on 8 March 2025, in which seven core experts participated. This was followed by two rounds of in-person advisory boards conducted on 31 May 2025 and 1 June 2025, respectively, which included 13 experts. The steering committee supervised evidence synthesis, ensured adherence to methodology, and aligned draft statements for the consensus process; no voting was conducted during the steering committee meeting.

During the advisory board rounds, voting was conducted anonymously using Slido (Cisco Systems Inc., California, US). No panelists dropped off between the rounds. The panelists were asked to indicate their agreement or disagreement with the proposed statements individually. Statements that failed to achieve consensus were revised or removed based on expert feedback and further discussion. The level of agreement was categorised as high (≥80%), moderate (60–80%), or low (<60%). Only statements that achieved a minimum of 80% agreement were accepted as consensus, consistent with the established standards in the Delphi-based consensus methodology. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess the level of evidence and strength of the recommendations [Table 1].[13] As the Delphi method involves only expert participants and not patient data, institutional review board (IRB) approval or informed consent was not required.

Table 1.

GRADE level of evidence and strength of recommendations

Strength of recommendation		Level of evidence
A	1a	Systematic review of RCTs, meta-analysis
	1b	Individual RCTs
B	2a	Systematic review of cohort studies
	2b	Individual cohort study (including low-quality RCT)
	3a	Systematic review of case-control studies
	3b	Individual case-control study
C	4	Case series (and poor-quality cohort and case-control studies)
D	5	Expert opinion

RCT: Randomised control trial; GRADE: Grading of Recommendations Assessment, Development and Evaluation

Reporting standards

The AGREE reporting checklist for consensus guidelines was used for qualitative development of this manuscript.

RESULTS

During the steering committee meeting held in March 2025, the expert panel (7 members) reviewed 27 draft statements spanning 10 thematic areas. Following initial evaluation, two statements were eliminated owing to redundancy, and three themes were removed owing to overlap or limited clinical relevance. This refinement resulted in 25 statements falling under seven themes that were used for consensus development.

In round 1 of the advisory board meetings (May 2025), which included 13 experts, five statements achieved unanimous consensus (100%) and were accepted without modification. The remaining 19 statements were revised based on expert feedback and carried forward to round 2. One statement was deleted because of lack of relevance. In round 2, 13 revised statements achieved 100% consensus, and one statement received 88% consensus and was accepted. Five statements were eliminated due to redundancy or thematic overlap. Statements that were modified or excluded during the consensus process are detailed in the Supplementary Tables 1–3.

Supplement Table 1.

Steering Committee meeting-statements and decisions

Statement Number	Statements	Decisions
Theme 1 - Need for monitoring Depth of Anaesthesia/Consciousness
Statement 1	Monitoring the depth of anaesthesia is recommended to support patient safety, reduce the risk of intraoperative awareness, and help minimize over-sedation and its associated side effects.
Statement 2	Intraoperative consciousness monitoring should be considered critical in high-risk populations as long-term alterations in brain function may occur following general anaesthesia which can significantly affect the quality of life.
Theme 2 - Current gaps in monitoring of anaesthesia
Statement 3	It is recommended that anaesthetic management should not rely solely on hemodynamic parameters as they are indirect and often unreliable indicators of anaesthetic depth.	Deleted
Statement 4	While conventional monitoring techniques provide valuable insights, they may not fully account for individual variability in pharmacokinetics and pharmacodynamics, which can influence anaesthetic drug concentrations. Incorporation of additional monitoring methods is recommended as it can support more precise anaesthetic management.	Merged with theme 1
Theme 3 - EEG based monitoring
Statement 5	EEG-based monitoring is recommended for assessing the depth of anaesthesia, as it offers a direct and objective measure of brain activity and may support more informed anaesthetic management.
Statement 6	It is suggested to use indices derived from EEG, such as the BIS, PSI, and Narcotrend Index, to guide anaesthetic titration. Among these, BIS is recommended as it is the most widely validated and clinically utilised tool due to its extensive evidence base and proven efficacy in optimising anaesthetic depth, reducing intraoperative awareness, and minimising postoperative complications.
Statement 7	BIS monitoring could be considered a standard of care for assessing the depth of anaesthesia due to its ability to provide real-time, objective measures of consciousness.
Theme 4 - Benefits of Intraoperative consciousness monitoring using BIS
Statement 8	BIS monitoring is recommended to help reduce the total dose of anaesthetics administered during surgery, which may lower the risk of haemodynamic instability, minimise drug-related complications, and support faster recovery.
Statement 9	Reduced Cognitive Dysfunction: BIS-guided anaesthesia is recommended to help reduce the incidence of postoperative delirium and cognitive dysfunction, particularly in elderly and high-risk patients. This may minimise the potential for long-term cognitive decline, which can impact quality of life.
Statement 10	Cost-effectiveness and improved quality of care: BIS monitoring should be considered as it optimises resource utilisation by reducing recovery time, minimising PACU stay, and decreasing anaesthetic wastage. This contributes to shorter overall hospital stays and earlier patient discharge, aligning with efforts to lower healthcare costs while maintaining high-quality care
Theme 5 - Benefits of Intraoperative consciousness monitoring using BIS
Statement 11	Total Intravenous Anaesthesia (TIVA): In the absence of measurable gas concentrations, BIS should be considered for monitoring brain activity and supporting precision sedation management.
Statement 12	Inhalational Anaesthesia: A combination of BIS and MAC should be considered as it enhances precision, reduces intraoperative awareness, and may help mitigate cognitive dysfunction, particularly in complex or high-risk cases.
Theme 6 - Indications for BIS monitoring – Based on ASA classification
Statement 13.a	In ASA I-II patients, BIS can be selectively used in surgeries where reduced anaesthetic doses, faster recovery is desirable or where precise anaesthesia monitoring is required.
Statement 13.b	Intraoperative consciousness monitoring should be considered critical in high-risk populations as long-term alterations in brain function may occur following general anaesthesia which can significantly affect the quality of life.
Theme 7 - Indications for BIS monitoring – Based on patient characteristics
Statement 14.a	BIS is recommended for patients of advanced age to reduce risks of postoperative complications such as delirium or cognitive dysfunction.
Statement 14.b	BIS is recommended for patients with significant comorbidities, including cardiovascular, respiratory, or metabolic conditions by supporting safer anaesthetic management through precise depth monitoring.
Statement 14.c	BIS is recommended for individuals with pre-existing neurological conditions or those requiring intraoperative neurological assessments to help balance sedation and functional monitoring, supporting the optimisation of anaesthetic depth.
Statement 14.d	BIS monitoring is useful in fine-tuning anaesthesia depth in young children, who cannot report awareness or discomfort, helping to achieve adequate sedation without overmedication.
Theme 8 - Indications for BIS monitoring – Based on Type of surgery
Recommendation 15.1.a	BIS is crucial for maintaining an optimal balance between sedation and real-time neurological assessments, enhancing both precision and safety during delicate procedures.
Recommendation 15.1.b	BIS is recommended for extensive cancer procedures to help minimise risks of hemodynamic instability and postoperative complications.
Recommendation 15.1.c	BIS is recommended in cardiac patients as it may be useful in predicting poor neurological outcomes in cardiac patients.
Recommendation 15.1.d	BIS may help support stable anaesthesia and smoother recovery during prolonged and high-risk procedures, providing better control over anaesthetic requirements.
Recommendation 15.1.e	BIS is indicated for trauma, obstetric, and emergency surgeries requiring precise anaesthetic depth management, contributing to improve overall patient safety.
Outpatient and day-care surgeries (15.2)
Recommendation 15.2	BIS monitoring facilitates rapid recovery and early discharge in short-duration surgeries, optimising patient flow and satisfaction.
Theme 9- Need for monitoring Depth of Anaesthesia/Consciousness
Statement 16	Implementation: BIS monitoring should be used as a complementary tool alongside other monitoring methods, such as haemodynamic parameters, to support comprehensive anaesthesia management and promote precise, individualised care.
Statement 17	Target BIS Range: A target BIS range of 40–60 is recommended during general anaesthesia to help balance adequate sedation and patient safety, aiding in the optimisation of the anaesthetic dose required for the procedure.
Statement 18	Special Considerations: In cases of hypothermia, muscle relaxant use, or neurological conditions, BIS values should be interpreted cautiously and correlated with clinical findings to maintain precise and tailored anaesthesia management.
Theme 10- Need for monitoring Depth of Anaesthesia/Consciousness
Statement 19	High-frequency activity in the DSA may indicate inadequate sedation, while excessive low-frequency activity suggests over-sedation.
Statement 20	Prolonged burst suppression should be avoided, as it is associated with increased risks of postoperative cognitive dysfunction and delayed recovery.
Statement 21	Clinical Correlation: BIS and DSA values should always be interpreted in conjunction with clinical parameters, including haemodynamic stability and patient-specific factors, to support optimal anaesthesia management and precision in anaesthetic delivery.

Supplement Table 3.

Advisory board round 2-statements and consensus.

Statement Number	Statements	Consensus (%)	Decisions
Theme 1 - Need for monitoring Depth of Anaesthesia/Consciousness
Statement 1	Monitoring the depth of anaesthesia is recommended to support patient safety, reduce the risk of intraoperative awareness, and help minimise over-sedation and its associated side effects.	100%	-
Statement 2	Intraoperative consciousness monitoring should be considered critical in high-risk populations as long-term alterations in brain function may occur following general anaesthesia which can significantly affect the quality of life.	100%	-
Statement 3	While conventional monitoring techniques provide valuable insights, they may not fully account for individual variability in pharmacokinetics and pharmacodynamics, which can influence anaesthetic drug concentrations. Incorporation of additional monitoring methods is recommended as it can support more precise anaesthetic management.	100%	-
Theme 2 - EEG based monitoring
Statement 4	EEG-based monitoring is recommended for assessing the depth of anaesthesia, as it offers a direct and objective measure of brain activity and may support more informed anaesthetic management.	100%	-
Statement 5	Various indices derived from EEG, such as the BIS, PSI, and Narcotrend Index, are available to guide anaesthetic titration. Among these, BIS is recommended as it is the most extensively validated and supported by a strong evidence base.	100%	-
Theme 3 - Benefits of Intraoperative consciousness monitoring using BIS
Statement 6	BIS monitoring is recommended to help reduce the total dose of anaesthetics administered during surgery, which may lower the risk of hemodynamic instability, minimize drug-related complications, and support faster recovery.	100%	-
Statement 7	Reduced Cognitive Dysfunction: BIS-guided anaesthesia is recommended to help reduce the incidence of postoperative delirium and cognitive dysfunction, particularly in elderly and high-risk patients. This may minimize the potential for long-term cognitive decline, which can impact quality of life.	100%	-
Statement 8	Cost-effectiveness and improved quality of care: BIS monitoring should be considered as it optimises resource utilisation by reducing recovery time, minimising PACU stay, and decreasing anaesthetic usage. This contributes to shorter overall hospital stays and earlier patient discharge, aligning with efforts to lower healthcare costs while maintaining high-quality care.	100%	-
Theme 4 – Indications for BIS monitoring- Based on type of anesthesia
Statement 9	Total Intravenous Anaesthesia (TIVA): In the absence of measurable gas concentrations, BIS is strongly recommended for monitoring brain activity and supporting precision sedation management.	100%	-
Statement 10	Inhalational Anaesthesia: BIS monitoring may be incorporated in addition to ETAG and MAC, as it enhances precision, reduces the risk of intraoperative awareness, and helps mitigate postoperative cognitive dysfunction in high-risk cases.	100%	-
Theme 5 - Indications for BIS monitoring – Based on patient characteristics
Statement 11.a	BIS is recommended for patients of advanced age to reduce risks of postoperative complications such as delirium or cognitive dysfunction.	100%	-
Statement 11.b	BIS is recommended for patients with significant comorbidities, including cardiovascular, respiratory, or metabolic conditions by supporting safer anaesthetic management through precise depth monitoring.	100%	-
Statement 11.c	BIS monitoring is useful in fine-tuning anaesthesia depth in young children, who cannot report awareness or discomfort, helping to achieve adequate sedation without overmedication.	88%	-
Theme 6 - Indications for BIS monitoring – Based on Type of surgery
High-risk surgeries (13.1)
Statement 12.1.a	BIS monitoring is recommended in neurosurgical procedures to ensure optimal anaesthesia (light), enabling real-time neurological assessments or evoked potential measurements while minimising the risks of over-sedation.	100%	-
Statement 12.1.b	BIS monitoring is recommended to optimise anaesthesia in extensive cancer procedures to help minimise risks of haemodynamic instability and postoperative complications.	-	Deleted
Statement 12.1.c	BIS monitoring is recommended in cardiac surgeries to ensure optimal anaesthetic depth, reduce the risk of neurological complications such as stroke and seizures, and minimise postoperative cognitive dysfunction.	100%
Statement 12.1.d	BIS monitoring is recommended for surgeries lasting over 2 hours, as maintaining the appropriate depth of anaesthesia becomes challenging, and the risk of anaesthetic overuse is higher.		Deleted
Statement 12.1.e	BIS monitoring is indicated for trauma, obstetric, and emergency surgeries requiring precise anaesthetic depth management, contributing to improving overall patient safety.	100%	-
Outpatient and day-care surgeries (13.2)
Statement 12.2	BIS monitoring facilitates rapid recovery and early discharge in short-duration surgeries, optimising patient flow and satisfaction.	-	Deleted
Theme 7- Usage Guidelines for BIS monitoring
Statement 13	Target BIS Range: A target BIS range of 40–60 is recommended during general anaesthesia to help balance adequate sedation and patient safety, aiding in the optimisation of the anaesthetic dose required for the procedure.	100%	-
Statement 14	Special Considerations: In cases of hypothermia, muscle relaxant use, or neurological conditions, BIS values should be interpreted cautiously and correlated with clinical findings to maintain precise and tailored anaesthesia management.	100%	-
Statement 15	EEG DSA may be recommended as an additional parameter to complement BIS as it enhances its value by providing more precise sedation monitoring. (personalised anaesthesia)	-	Deleted
Statement 16	BIS monitoring along with DSA may be recommended to enhance delirium screening and help helps mitigate post operative delirium, especially in high-risk patients.	-	Deleted
Statement 17	Prolonged burst suppression should be avoided, as it is associated with increased risks of postoperative cognitive dysfunction and delayed recovery.	100%

Supplement Table 2.

Advisory board round 1-statements, consensus and decisions

Statement Number	Statements	Consensus (%)	Decisions
Theme 1 - Need for monitoring Depth of Anaesthesia/Consciousness
Statement 1	Monitoring the depth of anaesthesia is recommended to support patient safety, reduce the risk of intraoperative awareness, and help minimise over-sedation and its associated side effects.	100%	-
Statement 2	Intraoperative consciousness monitoring should be considered critical in high-risk populations as long-term alterations in brain function may occur following general anaesthesia which can significantly affect the quality of life.	100%	-
Statement 3	While conventional monitoring techniques provide valuable insights, they may not fully account for individual variability in pharmacokinetics and pharmacodynamics, which can influence anaesthetic drug concentrations. Incorporation of additional monitoring methods is recommended as it can support more precise anaesthetic management.	100%	-
Theme 2 - EEG based monitoring
Statement 4	EEG-based monitoring is recommended for assessing the depth of anaesthesia, as it offers a direct and objective measure of brain activity and may support more informed anaesthetic management.	100%	-
Statement 5	Various indices derived from EEG, such as the BIS, PSI, and Narcotrend Index, are available to guide anaesthetic titration. Among these, BIS is recommended as it is the most extensively validated and supported by a strong evidence base.	-	Modified
Statement 6	BIS monitoring could be considered a standard of care for assessing the depth of anaesthesia due to its ability to provide real-time, objective measures of consciousness.	-	Deleted
Theme 3 - Benefits of Intraoperative consciousness monitoring using BIS
Statement 7	BIS monitoring is recommended to help reduce the total dose of anaesthetics administered during surgery, which may lower the risk of haemodynamic instability, minimise drug-related complications, and support faster recovery.	-	Modified
Statement 8	Reduced Cognitive Dysfunction: BIS-guided anaesthesia is recommended to help reduce the incidence of postoperative delirium and cognitive dysfunction, particularly in elderly and high-risk patients. This may minimise the potential for long-term cognitive decline, which can impact quality of life.	-	Modified
Statement 9	Cost-effectiveness and improved quality of care: BIS monitoring should be considered as it optimises resource utilisation by reducing recovery time, minimising PACU stay, and decreasing anaesthetic usage. This contributes to shorter overall hospital stays and earlier patient discharge, aligning with efforts to lower healthcare costs while maintaining high-quality care	-	Modified
Theme 4 – Indications for BIS monitoring- Based on type of anesthesia
Statement 10	Total Intravenous Anaesthesia (TIVA): In the absence of measurable gas concentrations, BIS is strongly recommended for monitoring brain activity and supporting precision sedation management.	-	Modified
Statement 11	Inhalational Anaesthesia: BIS monitoring may be incorporated in addition to ETAG and MAC, as it enhances precision, reduces the risk of intraoperative awareness, and helps mitigate postoperative cognitive dysfunction in high-risk cases.	100%	-
Theme 5 - Indications for BIS monitoring – Based on patient characteristics
Statement 12.a	BIS is recommended for patients of advanced age to reduce risks of postoperative complications such as delirium or cognitive dysfunction.	-	Modified
Statement 12.b	BIS is recommended for patients with significant comorbidities, including cardiovascular, respiratory, or metabolic conditions by supporting safer anaesthetic management through precise depth monitoring.	-	Modified
Statement 12.c	BIS monitoring is useful in fine-tuning anaesthesia depth in young children, who cannot report awareness or discomfort, helping to achieve adequate sedation without overmedication.	-	Modified
Theme 6 - Indications for BIS monitoring – Based on Type of surgery
High-risk surgeries (13.1)
Statement 13.1.a	BIS monitoring is recommended in neurosurgical procedures to ensure optimal anaesthesia (light), enabling real-time neurological assessments or evoked potential measurements while minimising the risks of over-sedation.	-	Modified
Statement 13.1.b	BIS monitoring is recommended to optimise anaesthesia in extensive cancer procedures to help minimise risks of haemodynamic instability and postoperative complications.	-	Modified
Statement 13.1.c	BIS monitoring is recommended in cardiac surgeries to ensure optimal anaesthetic depth, reduce the risk of neurological complications such as stroke and seizures, and minimise postoperative cognitive dysfunction	-	Modified
Statement 13.1.d	BIS monitoring is recommended for surgeries lasting over 2 hours, as maintaining the appropriate depth of anaesthesia becomes challenging, and the risk of anaesthetic overuse is higher.	-	Modified
Statement 13.1.e	BIS monitoring is indicated for trauma, obstetric, and emergency surgeries requiring precise anaesthetic depth management, contributing to improving overall patient safety.	-	Modified
Outpatient and day-care surgeries (13.2)
Statement 13.2	BIS monitoring facilitates rapid recovery and early discharge in short-duration surgeries, optimising patient flow and satisfaction.	-	Modified
Theme 7- Usage Guidelines for BIS monitoring
Statement 14	Target BIS Range: A target BIS range of 40–60 is recommended during general anaesthesia to help balance adequate sedation and patient safety, aiding in the optimisation of the anaesthetic dose required for the procedure.	-	Modified
Statement 15	Special Considerations: In cases of hypothermia, muscle relaxant use, or neurological conditions, BIS values should be interpreted cautiously and correlated with clinical findings to maintain precise and tailored anaesthesia management.	-	Modified
Statement 16	EEG DSA may be recommended as an additional parameter to complement BIS as it enhances its value by providing more precise sedation monitoring. (personalised anaesthesia)	-	Modified
Statement 17	BIS monitoring along with DSA may be recommended to enhance delirium screening and help helps mitigate post operative delirium, especially in high-risk patients	-	Modified
Statement 18	Prolonged burst suppression should be avoided, as it is associated with increased risks of postoperative cognitive dysfunction and delayed recovery.	-	Modified

Of the original 27 statements, 19 met the pre-defined consensus threshold (≥80% agreement) and were accepted. Eight statements were eliminated during this process [process illustrated in Figure 2]. The final set of themes and consensus statements is presented in Table 2.

Figure 2.

Consensus process flow chart. Adboard: Advisory board

Table 2.

Final set of themes and statements

Number	Statement	Consensus (%)	Level of Evidence	Strength of recommendation
Theme 1: Need for monitoring Depth of Anaesthesia/Consciousness
Statement 1	Monitoring the depth of anaesthesia is recommended to support patient safety, reduce the risk of intra-operative awareness, and help minimise oversedation and its associated side effects.	100	Level 2	High
Statement 2	Intra-operative consciousness monitoring should be considered critical in high-risk populations* as long-term alterations in brain function may occur following general anaesthesia which can significantly affect the quality of life.	100	Level 2	High
Statement 3	While conventional monitoring techniques† provide valuable insights, they may not fully account for individual variability in pharmacokinetics and pharmacodynamics, which can influence anaesthetic drug concentrations.	100	Level 1	High
Theme 2: Processed EEG Monitoring in Anaesthetic Practice
Statement 4	EEG-based monitoring is recommended for assessing the depth of anaesthesia as it offers a direct and objective measure of brain activity and may support more informed anaesthetic management.	100	Level 3	High
Statement 5	Various indices derived from EEG, such as the BIS, PSI, and Narcotrend Index, are available to guide anaesthetic titration. Among these, BIS is the most widely studied, adopted in clinical practice, and frequently referenced in the literature and guidelines.	100	Level 2	High
Theme 3 – Benefits of Intra-operative consciousness monitoring using pEEG
Statement 6	pEEG monitoring (such as BIS) is recommended to help reduce the total dose of anaesthetics administered during surgery, which may lower the risk of haemodynamic instability, minimise drug-related complications, and support faster recovery.	100	Level 1	High
Statement 7	pEEG-guided anaesthesia is recommended to help reduce the incidence of post-operative delirium, cognitive dysfunction, and post-operative nausea and vomiting (PONV), particularly in elderly and high-risk patients	100	Level 2	Moderate
Statement 8	pEEG monitoring may be considered to optimise resource utilisation by reducing recovery time, minimising PACU stay, and decreasing anaesthetic usage. However, its cost effectiveness in the Indian healthcare setting remains to be established and warrants further investigation.	100	Level 3	High
Theme 4 – Indications for pEEG monitoring – Based on type of anaesthesia
Statement 9	In TIVA, pEEG is strongly recommended for precisely titrating anaesthesia and helps prevent intra-operative awareness.	100	Level 2	High
Statement 10	Inhalational Anaesthesia: pEEG monitoring may be incorporated in addition to ETAG and MAC as it enhances precision, reduces intra-operative awareness risk, and helps mitigate post-operative cognitive dysfunction in high-risk cases.	100	Level 3	High
Theme 5 – Indications for pEEG monitoring – Based on patient characteristics
Statement 11. A	pEEG may be beneficial for geriatric patients to reduce risks of post-operative complications such as delirium, cognitive dysfunction.	100	Level 1	High
Statement 11. B	pEEG may be beneficial in titrating anaesthesia for patients with significant comorbidities, including cardiovascular, respiratory, or metabolic conditions by supporting safer anaesthetic management.	100	Level 1	High
Statement 11.C	pEEG monitoring requires further evaluation to establish its value in monitoring the depth of anaesthesia in paediatric patients.	88	Level 2	Moderate
Theme 6 – Indications for pEEG monitoring – Based on Type of surgery
Statement 12. A	pEEG monitoring is recommended in neurosurgical procedures performed under TIVA (particularly with IONM) to ensure optimal hypnotic depth.	100	Level 3	High
Statement 12. B	pEEG monitoring is recommended in complex cardiac surgeries to reduce the risk of neurological complications.	100	Level 3	High
Statement 12. C	pEEG monitoring may be considered in obstetric surgical procedures under general anaesthesia; however, its role requires further evaluation.	100	Level 3	High
Theme 7 – Usage Guidelines for BIS monitoring
Statement 13	The target BIS range of 40–60 should be evaluated along with waveform analysis (raw EEG/DSA) to determine optimal depth of anaesthesia.	100	Level 2	High
Statement 14	Special conditions in which BIS values should be interpreted cautiously and correlated with clinical findings and waveform analysis to maintain optimal anaesthesia are (not limited to): a. Hypothermia, b. NMB use, and c. drugs-Ketamine and Dexmedetomidine.	100	Level 2	High
Statement 15	Inadvertent prolonged burst suppression should be avoided.	100	Level 2	High

EEG: Electroencephalogram; BIS: Bispectral index; PSI: Patient state index; pEEG: Processed electroencephalogram; PACU: Post-anaesthesia care unit; TIVA: Total intravenous anaesthesia; ETAG: End-tidal anaesthetic gas; MAC: Minimum alveolar concentration; IONM: Intra-operative neuromonitoring; DSA: Density spectral array; NMB: Neuromuscular blockade

Multi-part statements addressing related clinical scenarios within a single domain are presented using sub-lettering (e.g., 11.a–c) for clarity and grouping.

*High-risk population here is defined by one or more of the following factors based on review of multiple papers:

1. Patient-related factors
   • Advanced age (≥65 years)
   • Significant comorbidities (American Society of Anesthesiologists Physical Status III or higher)
   • Cardiovascular, respiratory, hepatic, or renal dysfunction
   • Neurological disorders affecting brain responsiveness (e.g., stroke, epilepsy)
   • Extremes of body weight or metabolic abnormalities
   • Known or suspected difficult airway or risk of aspiration
2. Procedure-related factors
   • Major surgery (cardiac, thoracic, neurosurgical, vascular, upper abdominal)
   • Emergency or trauma surgery
   • Prolonged operative duration (>3 hours)
   • High blood loss or fluid shifts anticipated
   • Use of potent anaesthetic or sedative combinations
3. Anaesthetic-related factors
   • Use of total intravenous anaesthesia (TIVA) where end-tidal monitoring is unavailable
   • Previous history of intraoperative awareness
   • Anticipated need for precise titration of anaesthetic depth (e.g., in elderly or haemodynamically unstable patients)
     ^†Conventional monitoring techniques implies to conventional indicators of physiological and motor responses, such as:

• Non-invasive or invasive blood pressure monitoring
• Pulse oximetry (SpO₂) – for arterial oxygen saturation
• Capnography – for ventilation and end-tidal carbon dioxide (EtCO₂)
• Temperature monitoring
• Respiratory rate and airway pressure monitoring
• End-tidal anaesthetic gas concentration (for volatile agents)
• Clinical signs such as lacrimation, movement, muscle tone, and haemodynamic responses as indirect indicators of anaesthetic depth

International bodies recommend the use of pEEG or depth of anaesthesia monitoring in high-risk settings, particularly during TIVA and in patients at risk of awareness or post-operative cognitive complications.[5,6,7,8,9] The statements of our study are aligned with international guidance while being contextualised to address Indian practice settings.

DISCUSSION

Theme 1: Need for monitoring Depth of Anaesthesia/Consciousness

Consensus Statements:

1. Monitoring the depth of anaesthesia is recommended to support patient safety, reduce the risk of intra-operative awareness, and help minimise oversedation and its associated side effects.

2. Intra-operative consciousness monitoring should be considered critical in high-risk populations as long-term alterations in brain function may occur following general anaesthesia, which can significantly affect the quality of life.

3. While conventional monitoring techniques provide valuable insights, they may not fully account for individual variability in pharmacokinetics and pharmacodynamics, which can influence anaesthetic drug concentrations.

Evidence supporting the consensus/evidence-based scientific rationale

Intra-operative awareness is a serious and well-documented complication associated with general anaesthesia.[14] It occurs when anaesthetic depth is insufficient to induce unconsciousness, leaving patients vulnerable to awareness.[15] Indian studies report definite awareness rates ranging from 0.33% to 1.4% and possible awareness between 0.1% and 0.3%.[16,17] A meta-analysis by Gao et al. (N = 34,174) found that BIS-guided intravenous anaesthesia significantly reduced intra-operative awareness compared to conventional monitoring [odds ratio (OR) = 0.20, 95% confidence interval (CI) = 0.08–0.49, P = 0.0004].[14] In an Indian study [number of patients (N) = 100], BIS monitoring reduced awareness from 8% to 2%, reflecting a 75% relative reduction.[18] Oversedation is another critical concern during anaesthesia. BIS provides a reliable tool for titrating sedation depth and avoiding excessive anaesthetic dosing.[19] BIS-guided sedation using target-controlled propofol infusion achieved a plasma concentration of ≤1.2 μg/mL in 85% of patients (N = 107) undergoing elective surgeries under neuraxial anaesthesia, supporting its utility in maintaining safe and effective sedation.[20]

Aging brains are particularly vulnerable to anaesthetic exposure, which may lead to long-lasting neurological effects due to neurotoxicity and neuroapoptosis. Long-lasting impairments in cognitive function may occur in adult patients following general anaesthesia, particularly in those with pre-existing vulnerabilities or undergoing high-risk procedures.[21] BIS monitoring has been shown to help reduce emergence delirium by up to 22.3% (35.1% in the non-BIS group and 12.8% in the BIS group; P = 0.001; N = 163, aged 3–8 years) in high-risk populations[22] and also mitigate emergence agitation,[23] thereby preventing complications to the brain function, and improving patient quality of life.

Preventing intra-operative awareness in patients undergoing general anaesthesia can be challenging because the awareness recall can be identified only post-operatively by obtaining information directly from the patient. Conventional indicators of physiological and motor responses, such as high blood pressure, rapid heart rate, or movement, are often masked by concurrent administration of other drugs such as beta-blockers, calcium channel blockers, and neuromuscular blockers.[24] Pharmacokinetic (PK) studies in Indian adults show systematically different propofol disposition (lower volume of distribution and clearance compared with many Western cohorts), and attempts to validate population PK models in Indian patients demonstrate residual between-patient variability that models cannot predict for an individual.[25] Compared to conventional techniques, BIS-guided anaesthesia is associated with improved recovery metrics, including reduced eye opening time [mean difference (MD) = -1.34; P < 0.01], recovery time (MD = -1.99, P = 0.02), extubation time (MD = -2.54, P < 0.01), and hospital stays (MD = -7.11, P = 0.01).[26]

Theme 2: Processed EEG Monitoring in Anaesthetic Practice

Consensus Statements:

• 4. Electroencephalogram (EEG)-based monitoring is recommended for assessing the depth of anaesthesia as it offers a direct and objective measure of brain activity and may support more informed anaesthetic management.

• 5. Various indices derived from EEG, such as the BIS, PSI, and Narcotrend Index, are available to guide anaesthetic titration. Among these, BIS is most widely studied, adopted in clinical practice, and frequently referenced in the literature and guidelines.

Evidence supporting the consensus/evidence-based scientific rationale

EEG monitoring, although technically complex, offers valuable insights into hypnotic depth by capturing anaesthesia-induced changes in cerebral activity, including shifts in frequency and amplitude.[27] Evidence suggests that EEG-guided anaesthesia reduces the risk of intra-operative awareness and demonstrates comparable efficacy of end-tidal ETAG.[28] A study of 135 patients (aged 0–80 years) reported a statistically significant correlation between BIS values and raw EEG (R² = 0.063, P < 0.01),[27] indicating the accuracy of BIS in supporting clinical judgment. A 2022 prospective comparative study demonstrated that dexmedetomidine provided more stable BIS values and haemodynamic parameters during the intra-operative period compared to propofol and isoflurane (P < 0.05), supporting the role of BIS monitoring in guiding a more informed anaesthetic monitoring.[29]

While BIS is the most widely recognised and utilised pEEG-based index, alternatives like PSI and Narcotrend also offer utility in depth of anaesthesia monitoring.[30] Studies have indicated that PSI and Narcotrend can guide anaesthetic titration and depth assessment, although comparative data remain limited.[30,31,32] A prospective, parallel-group, single-centre study reported that PSI and BIS had similar clinical efficacy in terms of time of eye opening and recovery profile in patients undergoing elective spine surgery under neuromonitoring.[33] Nonetheless, BIS remains the most extensively studied and clinically adopted pEEG-based monitoring index. A PubMed search (2020–2025) using the keywords ‘bispectral index’ and ‘anaesthesia’ yielded a total of 251 articles on BIS. Eleven articles were retrieved for PSI, and 19 for Narcotrend, respectively [Table 3]. The predominance of BIS-related evidence reflects publication trends rather than exclusive superiority. Future studies should expand comparative evaluation across modalities, particularly in Indian settings.

Table 3.

Types and number of articles retrieved from the PubMed database for different EEG-based monitors.

Type of manuscript	BIS	PSI	Narcotrend
Systematic review and Meta-analysis	10	0	4
RCT	160	5	8
Observational studies	55	4	6
Review articles	5	2	1
Case studies/reports	21	0	0

RCT: Randomised control trial. BIS: Bispectral index; PSI: Patient state index

Theme 3: Benefits of Intra-operative Consciousness Monitoring Using pEEG

Consensus statements:

• 6. pEEG monitoring (such as BIS) is recommended to help reduce the total dose of anaesthetics administered during surgery, which may lower the risk of haemodynamic instability, minimise drug-related complications, and support faster recovery.

• 7. pEEG-guided anaesthesia is recommended to help reduce the incidence of post-operative delirium, cognitive dysfunction, and post-operative nausea and vomiting (PONV), particularly in elderly and high-risk patients.

• 8. pEEG monitoring may be considered to optimise resource utilisation by reducing recovery time, minimising post-anaesthesia care unit (PACU) stay, and decreasing anaesthetic usage. However, its cost-effectiveness in the Indian healthcare setting remains to be established and warrants further investigation.

Evidence supporting the consensus/evidence-based scientific rationale

BIS-guided anaesthesia can improve the patient’s quality of life by optimising the delivery of anaesthetics.[34] A meta-analysis by Gu Y et al. reported a significant reduction in anaesthetic drug usage with BIS monitoring compared to conventional methods [standardised mean difference (SD) = -0.39, P < 0.01].[26] In a retrospective study involving 3,819 patients on sevoflurane and 1,192 on desflurane, BIS monitoring was associated with a significant reduction of consumption of both drugs as compared to conventional monitoring (10.5 mL/h vs. 11.4 mL/h for sevoflurane; 17.4 mL/h vs. 20.2 mL/h for desflurane).[34] In a study of patients undergoing breast cancer surgery, sevoflurane consumption was significantly lower in the BIS group than in the control group (N = 25 per group; P = 0.019). These findings suggest that BIS monitoring may contribute to the reduced consumption of volatile anaesthetics. It is important to note that pEEG indices primarily reflect the hypnotic component of anaesthesia and do not directly assess analgesia; therefore, balanced anaesthesia with appropriate multimodal analgesic strategies remains essential. Additionally, BIS-guided anaesthesia was associated with faster recovery, including reduced time to eye opening (P = 0.001), motor response (P = 0.0001), and extubation (P = 0.085).[35] Goyal et al., in their prospective randomised controlled trial, reported that the recovery period was shorter with entropy use.[36]

Post-operative cognitive decline (POCD) is a significant yet poorly understood complication in elderly patients that often impacts recovery and quality of life.[37] A study conducted among 81 patients (65–75 years) who underwent anaesthesia with propofol and remifentanil reported that delirium was significantly lower in the BIS group (N = 41) compared to the non-BIS group (N = 40) (17.5% vs. 27.5%; P < 0.001).[38] Titrating anaesthetic agents using BIS has been shown to reduce the incidence of POCD across multiple anaesthetics.[37,39] Similarly, the aetiology of PONV in the early post-operative period includes exposure to volatile anaesthetics with a dose–response relationship.[40] In a 2017 systematic review and meta-analysis, the risk of PONV after surgery was reduced by 12% in patients monitored with BIS.[41] While several studies suggest a reduction in post-operative delirium and cognitive dysfunction with pEEG-guided anaesthesia, findings remain heterogeneous and population-dependent. Large trials such as ENGAGES (Effect of Electroencephalography-Guided Anesthetic Administration on Postoperative Delirium Among Older Adults Undergoing Major Surgery)[42] have reported mixed outcomes of EEG monitoring for the prevention of post-operative delirium among adults undergoing major surgery. Therefore, pEEG monitoring may be considered a supportive tool, rather than a definitive intervention in certain populations, to prevent these complications.

The cost-effectiveness of BIS monitoring remains a subject of debate. Despite the upfront costs, international studies have demonstrated that BIS monitoring may offer economic benefits by reducing anaesthetic usage, shortening hospital stay, and lowering complication rates.[43,44,45] In a prospective randomised comparative double-blinded study, patients monitored with BIS had faster awakening and less consumption of desflurane. Lower consumption of anaesthetic agents can lead to decreased cost.[46] The magnitude of economic benefits of BIS in India remains to be quantified, but according to our expert panel, it was recognised that the potential value of pEEG monitoring in India is mainly to enhance patient safety and improve the quality of care peri-operatively. It was discussed that inappropriate anaesthetic settings could lead to significant physical, psychological, and medico-legal implications, and monitoring techniques such as BIS lead to more efficient resource utilisation and improved recovery. The expert panel recommends that pEEG monitoring be considered a tool that supports individualised, safe, and sound clinical practice within the Indian context.

Also, enhanced recovery after surgery (ERAS) protocols have become important for encompassing the patient’s entire journey throughout the peri-operative period by combining modalities and treatments using an evidence-based approach.[47] ERAS society has suggested recommendations for optimum anaesthesia care for patients undergoing surgeries. In a prospective cross-sectional survey in India, it was reported that 89.4% of anaesthesiologists were aware of the concept of ERAS, and 32.2% anaesthesiologists did not monitor depth of anaesthesia routinely, and 11% used BIS.[47] Various ERAS pathways have incorporated BIS monitoring to enable continuous customisation of anaesthetic depth to individual patient needs and mostly a BIS index between 40 and 60 is recommended for maintenance of general anaesthesia.[28,48,49] In a 2023 prospective, randomised study, maintaining BIS between 40 and 60 resulted in a significantly shorter median time to eye-opening (4 min) compared with the MAC-guided group (5 min; P < 0.001). Similarly, the time to extubation was 8 min in the BIS group, compared to 11 min in MAC (p < 0.001).[50]

Theme 4 – Indications for pEEG monitoring – Based on type of anaesthesia

Consensus Statements:

• 9. In TIVA, pEEG monitoring is strongly recommended for precisely titrating anaesthesia and to help prevent intra-operative awareness.

• 10. Inhalational Anaesthesia: pEEG monitoring may be incorporated in addition to ETAG and MAC as it enhances precision, reduces intra-operative awareness risk, and helps mitigate post-operative cognitive dysfunction in high-risk cases.

Evidence supporting the consensus/evidence-based scientific rationale

Unlike inhalational anaesthesia, where ETAG and MAC provide validated surrogates of anaesthetic depth, TIVA lacks a direct measurable indicator of drug effect, increasing reliance on clinical signs and highlighting the role of pEEG monitoring.[51]

TIVA is popular owing to the favourable PK profiles of agents such as propofol and short-acting opioids such as remifentanil, along with the availability of target-controlled infusion (TCI) systems.[52] However, PK parameters may vary across patient populations, and available data from Indian cohorts are limited and derived from specific clinical settings; therefore, these findings may not be generalisable to all patient groups. Unlike inhalational anaesthesia, TIVA lacks a real-time measure of exhaled drug concentration, making reliance on clinical sign monitoring alone insufficient, particularly under neuromuscular blockade.[53]

In a large multi-centre, double blind randomised trial involving 5,220 patients receiving propofol-based TIVA, the incidence of confirmed awareness was 0.14% in the BIS-guided group compared with 0.65% in the control group (p = 0.002; OR 0.21), representing a 78% reduction in intra-operative awareness with BIS monitoring.[54] pEEG monitoring serves as a critical safety measure against accidental awareness under general anaesthesia (AAGA), especially during TIVA. Comparative studies evaluating BIS, PSI, and entropy monitoring have demonstrated similar effectiveness in predicting anaesthetic depth.[55,56] Since some patient subgroups are particularly vulnerable to inappropriate anaesthetic dosing and not all at-risk populations are easily identifiable, routine use of pEEG in TIVA provides both precision and an additional safeguard against awareness.[57]

To improve intra-operative monitoring of the depth of anaesthesia, BIS, ETAG, and MAC monitoring can be used along with clinical monitoring.[58] Anaesthesia with volatile anaesthetics guided by BIS can reduce intra-operative awareness by optimising anaesthesia delivery.[34] In a prospective, randomised, double-blinded study of patients undergoing lumbar spine surgeries, anaesthesia was guided by BIS values of 45–55 and allowed 20% variation in cardiovascular parameters from the baseline. Both BIS and ETAG-guided anaesthesia resulted in a significant reduction in emergence time, extubation time, and time to name recall. Specifically, the mean emergence time in ETAG (5.1 ± 1.53 min) and BIS (5.0 ± 2.12 min) guided groups was significantly lower than that in the standard group (7.5 ± 2.90 min). The extubation time in the ETAG (6.3 ± 2.22 min) and BIS-guided group (6.5 ± 1.78 min) was significantly lower than that in the standard group (9.0 ± 3.20 min) (p < 0.001). The time to achieve a fast track score of more than 12 was significantly less in the BIS-guided group (13.12 ± 2.59 min), facilitating earlier discharge.[59] In another study among 163 children undergoing inhalational anaesthesia, randomised to the BIS group (n = 86) and control group (n = 77; anaesthesia based on MAC and ETAG), the BIS group had a significantly reduced emergence delirium (12.8%) compared to the control group (35.1%) (P < 0.001).[22]

Theme 5 – Indications for pEEG monitoring – Based on patient characteristics

Consensus Statements:

• 11.a. pEEG may be beneficial for geriatric patients to reduce risks of post-operative complications such as delirium or cognitive dysfunction.

• 11.b. pEEG may be beneficial in titrating anaesthesia for patients with significant comorbidities, including cardiovascular, respiratory, or metabolic conditions, by supporting safer anaesthetic management.

• 11.c. pEEG monitoring requires further evaluation to establish its value in monitoring the depth of anaesthesia in paediatric patients.

Evidence supporting the consensus/evidence-based scientific rationale

Post-operative delirium (POD) affects 15–53% of surgical patients over 65 years of age,[60] with intensive care unit (ICU) admission, increasing the incidence to 70–87%.[61] A meta-analysis of patients aged >60 years undergoing surgery found that BIS monitoring significantly reduced the incidence of POD (OR = 1.32; 95% CI: 1.11–1.57; P = 0.001) compared to conventional monitoring.[62] A randomised controlled trial of 921 patients >60 years, with BIS guidance (BIS 40–60), had delirium rates of 15.6% versus 24.1% in routine care, with an absolute reduction of nearly 9% (p = 0.01). The same study reported reduced POCD rates at 3 months of 10.2% in the BIS group versus 14.7% in routine care.[63] In every 1,000 elderly patients undergoing major surgery, titrating anaesthetic delivery to maintain a BIS range of 40–60 could prevent approximately 23 cases of POCD and 83 cases of delirium.[63] A Cochrane review of six randomised controlled trials (N = 2,929) concluded that pEEG monitoring likely reduces POD within 7 days [risk ratio (RR) = 0.71] and POCD at 12 weeks post-operatively (RR = 0.71).[64]

BIS facilitates individualised anaesthetic titration, particularly in patients with haemodynamic instability, comorbidities (e.g., cardiovascular, respiratory, metabolic), trauma, and old age.[65,66] In a randomised study of 40 patients undergoing off-pump coronary artery bypass grafting, BIS-guided anaesthesia (BIS 50) resulted in a 35.2% reduction in isoflurane and 32% reduction in propofol usage (P < 0.05), contributing to reduced myocardial depression and improved haemodynamic stability.[66]

The ‘Anaesthetic Depth and Complications After Major Surgery’ trial randomised patients aged ≥60 years with ASA class III–IV to BIS-guided light (BIS 50) or deep (BIS 35) anaesthesia. While the 1-year mortality was similar, the lighter group received ~30% less volatile anaesthetic and maintained higher mean arterial pressures, supporting the safety of lighter pEEG-guided depths in comorbid patients.[65] High-quality trials summarised in Cochrane reviews revealed that BIS-guided anaesthesia reduces anaesthetic consumption (propofol by 1.44 mg/kg/h, volatile agents by 0.14 MAC) and shortens recovery time (e.g., extubation by 2.87 min, eye opening by 2.14 min), along with fewer episodes of intra-operative awareness in higher-risk patients with somatosensory evoked potentials (SSEPs).[67]

Due to rapid neurodevelopment, anaesthetic requirements in children vary across age groups. EEG monitoring provides a non-invasive method to assess cerebral activity and anaesthetic depth during these transitions.[68] However, the limitations in accuracy and reliability across paediatric age groups highlight the need for further evaluation of pEEG monitoring in children.[69]

Evidence from a prospective, double-blind randomised controlled trial in 3–8-year-old patients undergoing adenoidectomy reported that targeting anaesthesia depth via BIS significantly reduced the incidence of emergence delirium from 35.1% (MAC-guided) to 12.8% (BIS-guided), with lower Pediatric Anaesthesia Emergence Delirium (PAED) scores at 10 and 30 minutes post-operatively (p = 0.001).[22] In contrast, a randomised trial in healthy children aged 2–12 years undergoing ambulatory surgery showed no significant difference in sevoflurane exposure (mean end-tidal 1.8%), BIS values, recovery times, or emergence agitation when BIS values were visible versus concealed, with time to meet discharge criteria remaining similar between the groups.[69]

Since BIS algorithms are based on adult EEG patterns, their reliability in infants (<6 months) is limited due to immature EEG features and poor correlation with anaesthetic depth.[70] Additionally, greater inter-individual variability in BIS values and inconsistent relationships with end-tidal anaesthetic concentration further challenge its reliability across paediatric ages.[69]

Theme 6 – Indications for pEEG monitoring – Based on Type of surgery

Consensus Statements:

• 12.a. pEEG monitoring is recommended in neurosurgical procedures performed under TIVA (particularly with intra-operative neuromonitoring (IONM)) to ensure optimal hypnotic depth.

• 12.b. pEEG monitoring is recommended in complex cardiac surgeries to reduce the risk of neurological complications.

• 12.c. pEEG monitoring may be considered in obstetric surgical procedures under general anaesthesia; however, its role requires further evaluation.

Evidence supporting the consensus/evidence-based scientific rationale

Based on institutional protocols and evidence from a large series of 3,112 neurosurgical and spinal procedures with IONM, EEG changes, including burst suppression or excessive lighting, prompted timely anaesthetic adjustments in 90% of alerts and 80% of notifications, with subsequent restoration of IONM signals to baseline in most cases.[71] In a prospective study of 120 idiopathic scoliosis surgeries, BIS-guided TIVA enabled “real-time” IONM, optimal recording conditions, reduced surgery time by 1 hour, and improved intra-operative communication, while maintaining safety.[72]

Although SSEPs and EEG provide strong prognostic value post-cardiac arrest, their use is time-intensive, and the early prediction of neurological deficits remains challenging. BIS offers a rapid, standardised assessment with automated suppression ratio analysis.[73] In a retrospective study of 292 adult patients undergoing major aortic surgery, a decrease in BIS by >25% from baseline was strongly associated with increased rates of POD and neurological events, significantly longer ICU stay, and prolonged intubation.[74] Furthermore, BIS and suppression ratio (SR) monitoring within the first four hours after resuscitation predicted unfavourable neurological outcomes with 89.5% specificity and 85.7% sensitivity. Each 1-point increase in BIS reduced the risk of poor outcome by 7.9%, while each 1-point increase in SR increased the risk by 8.1%.[73]

Caesarean sections pose a risk of inadequate anaesthesia due to rapid induction, limited use of opioids/benzodiazepines, and restricted volatile agent dosing.[59] A 2004 study reported an awareness risk with sevoflurane ranging from 20% to 45%.[75] Studies have shown that up to 20% of participants may exhibit BIS values above 60, which is associated with an increased risk of intra-operative awareness despite standard anaesthetic protocols.[76] A 2021 randomised trial in 80 elective caesarean sections found that 7 mg/kg thiopental produced lower BIS values from skin incision to delivery (36.9 ± 4.4 vs. 39.7 ± 6.8; P = 0.02) and fewer isolated forearm technique (IFT) responses, indicating deeper hypnosis, but at the cost of lower 1 min Apgar scores (≤ 7 in 47.5% vs. 5%; P < 0.001) and poorer neonatal neurobehavioural outcomes. Although BIS effectively assessed anaesthetic depth, adequate BIS values did not consistently prevent positive IFT responses, indicating the need for complementary monitoring in obstetric anaesthesia.[77]

Theme 7 – Usage Guidelines for BIS monitoring

Consensus Statements:

• 13. The target BIS range of 40–60 should be evaluated along with waveform analysis [raw EEG/density spectral array (DSA)] for guiding optimal depth of anaesthesia.

• 14. Special conditions in which BIS values should be interpreted cautiously and correlated with clinical findings and waveform analysis to maintain optimal anaesthesia are (not limited to): a. Hypothermia, b. Neuromuscular blockade use, and c. drugs – ketamine and dexmedetomidine.

• 15. Inadvertent prolonged burst suppression should be avoided.

Evidence supporting the consensus/evidence-based scientific rationale

The BIS algorithm interprets raw EEG data and provides anaesthesiologists with a dimensionless value ranging from 0 to 100, where 0 indicates suppressed EEG activity and 100 indicates a fully awake state.[78] A BIS range of 40–60 is recommended during general anaesthesia to minimise the risk of intra-operative awareness.[78,79] Therefore, BIS values between 40 and 60 help determine the amount of anaesthetic to be administered to the patient.[80] BIS in patients with high-risk awareness, performed within a range of 40–60, indicated that only 0.24% of the patients (7/2861) reported awareness.[81] An Indian study involving 30 adult patients (aged 20–65 years) reported no cases of intra-operative awareness when the BIS values were maintained between 40 and 60.[82] Therefore, a BIS range of 40–60 can help guide in providing an optimal depth of anaesthesia.

Reliable interpretation of BIS values requires adequate signal acquisition and minimal artefact. Values should be interpreted when the signal quality index (SQI) is adequate (commonly ≥80% as per manufacturer guidance) and in the presence of stable raw EEG waveforms. Elevated electromyographic activity may falsely increase BIS values; therefore, readings obtained during high EMG activity should be interpreted with caution. Similarly, sustained SR reflects excessive hypnotic depth, particularly in elderly patients, and should prompt re-assessment of anaesthetic dosing. No universally validated thresholds exist, and interpretation should always be integrated with clinical context and waveform analysis.

The DSA provides a time-compressed, colour-coded view of the EEG that enables anaesthesiologists to visualise cortical activity in real time. By displaying how the power within different frequency bands evolves over time, DSA complements processed indices such as BIS and adds clinical context that a single number alone cannot convey.[83,84] Typical oscillatory patterns like slow-delta and alpha coupling during adequate hypnosis, attenuation of alpha activity with lightening, and the appearance of burst suppression at excessive depth all can be easily recognised on the spectrogram.[84,85] This pattern recognition also helps distinguish the EEG signatures of various drug classes, such as gamma-aminobutyric acid (GABA), N-methyl-D-aspartate (NMDA)-antagonist, and α₂-agonist agents, which are not reliably reflected by processed indices.[84] Because muscle artefacts or neuromuscular blockade can distort index values, simultaneous interpretation of the raw EEG and DSA allows for more confident titration of anaesthetic depth.[86] Clinical data further support BIS use with DSA, showing comparable overall delirium detection to the 3-minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) and greater sensitivity in patients with dementia (83% vs 50%; p = 0.04).[87] In practice, maintaining BIS values between 40 and 60 while reviewing the DSA offers a pragmatic strategy for ensuring adequate hypnosis and minimising the risks of awareness or post-operative delirium. Continued research and training are needed to refine DSA interpretation across different agents, age groups, and clinical scenarios.[83,84,86]

Special conditions

Profound hypothermia can affect the EEG, leading to varying BIS readings.[88] Hypothermic arrest may also lead to cerebral tissue hypoxia, delaying the restoration of the BIS values.[88] A German study involving 30 patients found that deep hypothermia reduced BIS values linearly by approximately 1.8 units per 1°C drop in temperature.[89] Neuromuscular blockade is a contributing factor for intra-operative awareness during general anaesthesia. BIS values decrease with the use of neuromuscular blockers,[90] and neuromuscular blockade reversal increases BIS values in patients undergoing general anaesthesia.[91] However, in 2020, a small study conducted among 35 children showed that neuromuscular blocking drugs caused minor changes in the BIS values.[92]

Ketamine–propofol combinations may paradoxically increase BIS values despite deepening hypnosis, complicating interpretation.[93] A study of 40 patients undergoing caesarean section reported that the mean BIS value in the dexmedetomidine group was lower than that in the control group (P < 0.001). Still, the BIS value was maintained between 40 and 60 in the dexmedetomidine group throughout the surgery period.[94] Dexmedetomidine produces characteristic EEG patterns (including spindle activity and alpha–theta dominance) that may lower BIS values without necessarily reflecting equivalent hypnotic depth; therefore, BIS interpretation should be integrated with raw EEG waveform analysis and the clinical context.

Influence of additional factors on BIS readings

Index values may increase with administration of nitrous oxide (N₂O) and EMG artifacts/electrocautery underestimating the true depth of anaesthesia. N₂O (60–70%) has a MAC of 0.55–0.65 and, when combined with inhalational agents, provides additive anaesthetic effects.[95] But administration of N₂O is associated with increased beta oscillations and decreased alpha and delta activity in the frontal lobes.[96] Mishra et al. reported that with addition of 60% N₂O, there was a significant increase in BIS values at 1.0 MAC for sevoflurane and desflurane (P = 0.44).[97] pEEG-based indices utilise waveforms of small amplitudes. High-frequency electromagnetic noise, such as those generated by electrocautery, also interfere with BIS measurements.[98] A 2023 comparative study also demonstrated that both PSI and BIS were affected by EMG artifacts under steady-state sevoflurane anaesthesia.[99]

Burst suppression is characterised by alternating periods of flat EEG and bursts of slow-wave activity, along with an elevated SR.[100] Sustained SR values should alert the clinician to excessive anaesthetic depth, particularly in elderly or high-risk patients. Burst suppression has been associated with POD in some studies, although the strength and consistency of this relationship remain uncertain.[100] Inadvertent burst suppression from deep sedation in critically ill patients may even lead to death.[101,102,103] Inadvertent burst suppression has also been reported with a prevalence of 69.6% (78 out of 112 study participants) in a study from the United States.[104] The study also showed that in people with delirium (N = 10, 8.9%), intra-operative burst suppression was more prevalent (100%) compared to other study participants (66.7%) (P = 0.03).[104] Therefore, avoiding burst suppression can improve outcomes in both intra-operative and critical care settings.[105] When inadvertent burst suppression is detected, anaesthetic dosing should be re-assessed and titrated downward where clinically appropriate, while ensuring adequate analgesia and haemodynamic stability. Concurrent evaluation of contributing factors such as hypothermia, drug interactions, or excessive hypnotic administration is recommended. Continuous interpretation of raw EEG and DSA, in conjunction with processed indices, can support timely adjustments and help avoid prolonged periods of deep anaesthesia.

EEG sensors have limitations in terms of electrode size and positions because of their fixed design. Multiple studies reinforce the practice of using standard bifrontal montage with proper skin preparation and low impedance to ensure reliable signal acquisition.[106,107,108] Due to blood, cleaning solution and closeness of forehead sensor to the surgical site can interrupt pEEG recording.[109] Certain studies have analysed non-frontal BIS sensor placements and standard forehead/temporal montages when the frontal site is inaccessible.[109]

In a prospective study, a total of 20,784 paired measurements of response entropy (RE) and state entropy (SE) were analysed. Bland–Altman analysis showed a mean difference of 0.37 for RE (95% LOA − 7.09 to 7.88) and 0.69 for SE (95% LOA − 5.95 to 7.31), with only 3.46% of RE and 3.40% of SE values outside the limits. Strong positive correlations were observed: RE r = 0.983, SE r = 0.984 (P < 0.05). The sensitivity, specificity, and test efficiency were RE: 98.1%, 93.3%, 97.1%; SE: 99.2%, 95.1%, 98.5%, respectively, demonstrating that intra-orbital entropy sensor placement is a reliable and effective alternative.[110] These findings are also supported by a systematic review of 12 prospective observational studies.[111] A 2023 study by Abdelrahman et al. on patients for elective renal operations showed that BIS values were comparable between the frontal and post-auricular positions at LOC, intubation, 60, 120, and 80 min, and at emergence. A strong link between the two sensor positions was indicated by the correlation coefficient (r = 0.607, p < 0.001).[109]

Although alternative sensor placements (e.g., intra-orbital or post-auricular) have been explored in selected studies and have demonstrated reasonable correlation with standard frontal montage, these approaches require further validation and should not replace standard bifrontal placement in routine clinical practice.

Towards an India-Specific Evidence Base for pEEG-Guided Anaesthesia

The present consensus serves as a channel for advancing intra-operative anaesthesia monitoring in India. The current evidence base and literature available on pEEG monitoring including BIS largely originates from foreign studies. The expert panel confirmed that this paucity of India-specific data is an opportunity to bridge current knowledge gaps, and by establishing the “Indian Expert Consensus on Intraoperative Consciousness Monitoring Using Processed EEG (pEEG) Based Indices”, a structured framework can be provided for wider adoption of pEEG monitoring across varied clinical environments. Our recommendations also align with guidance from ASA, NICE, and ESA, while incorporating India-specific considerations such as resource variability and training gaps.

The panel also acknowledged that the conditions in India differ markedly from economically richer countries with many hospitals and surgical facilities operating in resource-limited settings where availability of resources, infrastructure, and financial restraints may limit routine pEEG use. Therefore, routine universal deployment of pEEG monitors across all operating theatres may not be feasible at present; prioritisation in elderly patients, high-risk populations, and cases conducted under TIVA may represent a pragmatic and context-appropriate implementation strategy in India.

As more Indian institutions and healthcare providers begin to utilise pEEG-based indices in their surgical setup, real-world data will emerge, and these recommendations will be further validated and refined. This will also enable to quantify cost benefits and patient outcome studies that will reflect the unique demography, infrastructural, and economic diversity of the Indian healthcare system and will promote evidence-based anaesthesia practice in future. A stepwise approach for implementing BIS/pEEG monitoring and a simplified algorithm for intra-operative anaesthesia monitoring using pEEG-based indices are presented in Appendix 2 and Appendix 3, respectively.

Limitations of pEEG monitoring

pEEG monitoring has important clinical utility; however, several limitations must be recognised. Availability across operating theatres in India remains variable, particularly in resource-constrained settings, and universal application may not be feasible. Although multiple studies suggest benefits in selected populations, large trials such as ENGAGES and ADAPT-2 (Anaesthetic Depth and Postoperative Delirium Trial-2) have shown inconsistent effects on post-operative delirium, underscoring that pEEG should be considered an adjunct rather than a replacement for comprehensive peri-operative management. pEEG indices primarily reflect hypnotic depth and do not directly assess analgesia; therefore, balanced anaesthesia remains essential. Technical factors such as electrocautery interference, electromyographic activity, signal artefacts, and drug-specific EEG effects (e.g., ketamine, dexmedetomidine) may influence index values, and interpretation should always be integrated with raw EEG patterns and clinical judgement. These consensus recommendations reflect expert agreement based on current evidence and are intended to guide, not mandate, clinical practice.

Future directions and implementation considerations in India

The progress of this consensus is also dependent on continued education, awareness, and clinical integration efforts. Capacity-building initiatives, including structured training programmes and workshops, are essential to improve clinician familiarity and confidence in interpreting pEEG data. Future efforts should focus on developing standardised training frameworks and integrating pEEG education into anaesthesia training curriculum and continuing medical education programmes. These programmes can be supported by industry-academic partnerships and should aim to expand the use across tertiary as well as tier 2 and 3 healthcare centres. Simultaneously, hospital-based audits and multi-centre studies should be encouraged to generate Indian-specific data. Such initiatives will together strengthen the practical foundation of pEEG-guided anaesthesia and accelerate its acceptance in modern peri-operative care in India.

CONCLUSION

This expert consensus underscores the urgent need for Indian anaesthesia practice to transition from reliance on conventional clinical signs to evidence-based cerebral monitoring. pEEG monitoring, particularly BIS monitoring, has consistently demonstrated benefits in enhancing anaesthetic titration, reducing intra-operative awareness, lowering post-operative delirium and cognitive decline, and supporting faster recovery. By establishing India-specific recommendations on target ranges, indications, and usage pathways, these guidelines provide a practical framework for anaesthesiologists to adopt pEEG in routine care. Implementing these recommendations into practice can improve patient safety, optimise resource use, and align Indian practices with international benchmarks for peri-operative excellence.

Conference presentation statement

Presented as an oral paper at ISA WORLD SIVA CONGRESS 2025, Chandigarh, India, 26 July 2025.

Study data availability

De-identified data may be requested with reasonable justification from the authors and shall be shared after approval.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

No artificial intelligence (AI) tools-assistive/ generative were used in the preparation and analysis of the manuscript.

Author contributions

SJSB, SK, TLK, JT, NG and VS were involved in the study’s conception and design. SJSB, SK, TLK, JT, MSK, NG, APH, VS, GK, AK, SC, RS, MK, SKS, SRKG and RC contributed to the analysis and interpretation of data and the literature review. All authors were involved in drafting the manuscript, critically revising it for important intellectual content, and approving the final version for publication.

Informed consent

No informed consent was required as human participants and/or animals were not involved in the study.

Supplementary material

This article has supplementary material and can be accessed at this link. Supplementary Material at http://links.lww.com/IJOA/A74.

Conflicts of interest

Nil.

APPENDIX 1

Steering committee panelists (Core group)

1. Dr. Sukhminder J Bajwa (Dean and Principal, Maharishi Markandeshwar College of Medical Sciences and Research, Ambala, Haryana, India)

2. Dr. Sangeeta Khanna (Senior Director, Department of Critical Care and Anaesthesiology, Medanta- The Medicity, Gurgaon, India)

3. Dr. Ti Lian Kah (Director of Cardiac Anaesthesia, Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore)

4. Dr. Vijay Shetty (Director, Department of Anaesthesia, Fortis Hospital, Mulund, Mumbai, India)

5. Dr. Nishkarsh Gupta (Additional Professor, Onco-anaesthesia and Palliative Medicine, Dr. BRAIRCH, AIIMS, Delhi, India)

6. Dr. Abhijit Kumar (Assistant Professor, Department of Anaesthesiology, AIIMS Kalyani, Delhi, India).

Advisory Board Meeting Panelists:

1. Dr. Sukhminder Jit Singh Bajwa (Dean and Principal, Maharishi Markandeshwar College of Medical Sciences and Research, Ambala, Haryana, India)

2. Dr. Sangeeta Khanna (Senior Director, Department of Critical Care and Anaesthesiology, Medanta- The Medicity, Gurgaon, India)

3. Dr. Ti Lian Kah (Director of Cardiac Anaesthesia, Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore)

4. Dr. Jithendra T (Senior Consultant Anaesthesiologist and Intensivist, Neuroanaesthesia and Neurocritical Care, Aster Medcity, Kochi, India)

5. Dr. Ajay Prasad Hrishi (Additional Professor and Program-In-Charge, Neuroanaesthesia and Neurocritical Care, SCTIMST, Thiruvananthapuram, India)

6. Dr. Nishkarsh Gupta (Additional Professor, Onco-anaesthesia and Palliative Medicine, Dr. BRAIRCH, AIIMS, Delhi, India)

7. Dr. Gaurav Kakkar (Lead and Senior Consultant, Neuroanaesthesia and Neurocritical Care, Amrita Hospital and Amrita School of Medicine, Faridabad)

8. Dr. Vijay Shetty (Director, Department of Anaesthesia, Fortis Hospital, Mulund, Mumbai, India)

9. Dr. Abhijit Kumar (Assistant Professor, Department of Anaesthesiology, AIIMS Kalyani, Delhi, India)

10. Dr. Swati Chhabra (Additional Professor, Department of Anaesthesiology and Critical Care, AIIMS Jodhpur, India)

11. Dr Ridhima Sharma (Associate Professor, Department of Anaesthesiology and Critical Care, AIIMS Nagpur, India)

12. Dr. Muralidhar Kanchi (Director and Principal, Anaesthesia and Intensive Care, Narayana Hrudayalaya Institute of Allied Health Sciences)

13. Dr. Sarah K. Saxena (Anesthesiologist, Department of Anaesthesia, Helora, Mons, Belgium)

14. Prof. Suresh Rao K.G (Co-Director of the Institute of Heart and Lung Transplant and Mechanical Circulatory Support, HOD and Senior Consultant, MGM Healthcare, Chennai)

15. Dr Ripon Choudhary (Associate Professor, Department of Anaesthesiology and Critical Care, AIIMS Nagpur, India).

Appendix 2.

Stepwise Approach for Implementing BIS/pEEG Monitoring. EMG: Electromyography; BMI: Body mass index; ERAS: Enhanced recovery after surgery; pEEG:Processed electroencephalography; NMB:Neuromuscular blocker; TIVA: Total intravenous anaesthesia; yrs:Years; EEG:Electroencephalography; DSA: Density spectral array; BIS: Bispectral index

Appendix 3.

Simplified algorithm for intra-operative anaesthesia monitoring using pEEG-based indices. The flow outlines patient selection, monitoring workflow, interpretation, and implementation steps for safe and individualised anaesthetic management. ASA: American Society of Anesthesiologists; EEG: Electroencephalography; pEEG: Processed electroencephalography; NMB: Neuromuscular blocker; DSA: Density spectral array; BIS: Bispectral index; PSI: Patient state index; TIVA: Total intravenous anaesthesia; EMG: Electromyography

Funding Statement

Nil.