Depth of anaesthesia monitors (E-Entropy, BIS and Narcotrend)

343 Pages·2012·3.2 MB·English

Technology Assessment Report commissioned by the NIHR HTA
Programme on behalf of the National Institute for Health and
Clinical Excellence – Diagnostics Assessment Report

Depth of anaesthesia monitoring (E-Entropy, Bispectral Index and Narcotrend)

Produced by Southampton Health Technology Assessments Centre
(SHTAC), University of Southampton

Authors Jonathan Shepherd
Jeremy Jones
Geoff Frampton
Jackie Bryant
Louise Baxter
Keith Cooper

Correspondence to Jonathan Shepherd
Date completed 2nd April 2012

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Source of funding: This report was commissioned by the NIHR HTA Programme as project
number 11/57

Declared competing interests of the authors

None

Acknowledgements

We would like to thank members of our advisory group panel who provided expert advice and
comments on the protocol and a draft of this report:

Professor Brian Pollard, Professor of Anaesthesia, Manchester Royal Infirmary, UK.
(Professor Pollard has in the past received funding from Aspect Medical, the manufacturers of
the BIS monitor to undertake some research using the BIS monitor).

Marta Soares, Research Fellow, Centre for Health Economics, University of York, UK

Dr Gerlinde Mandersloot, Consultant in Intensive Care and Anaesthesia, The Royal London
Hospital Whitechapel, UK (Representing ICU Steps – The Intensive Care Patient Support
Charity)

We are also grateful to Karen Welch, Information Scientist, SHTAC, University of
Southampton, for generating and running the literature searches and Andy Clegg, Professor of
Health Services Research, SHTAC, University of Southampton, for reviewing a draft of this
report.

Rider on responsibility for report
The views expressed in this report are those of the authors and not necessarily those of the
NIHR HTA Programme. Any errors are the responsibility of the authors.

This report should be referenced as follows:

J Shepherd, J Jones, G Frampton, J Bryant, L Baxter, K Cooper. Depth of anaesthesia
monitoring (E-Entropy, Bispectral Index and Narcotrend) Health Technology Assessment
2012

Contributions of authors

J Shepherd (Principal Research Fellow) developed the research protocol, assisted in the
development of the search strategy, assessed studies for inclusion, extracted data from and
quality assessed included studies, synthesised evidence, drafted and edited the final report,
and project managed the study.

J Jones (Principal Research Fellow) developed the research protocol, assessed studies for
inclusion, extracted data from and quality assessed included studies, synthesised evidence,
developed the economic evaluation, and drafted the final report.

G Frampton (Research Fellow) assessed studies for inclusion, extracted data from and quality
assessed included studies, synthesised evidence, and drafted the final report,
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L Baxter (Research Fellow) assessed studies for inclusion, extracted data from and quality
assessed included studies, synthesised evidence, assisted in developing the economic
evaluation and drafted the final report.

J Bryant (Principal Research Fellow) developed the research protocol, contributed to the
background section, extracted data from and quality assessed included studies, synthesised
evidence, drafted and edited the final report.

K Cooper (Senior Research Fellow) assessed studies for inclusion, extracted data from and
quality assessed included studies, synthesised evidence, and developed the economic
evaluation.

Commercial in confidence information highlighted and underline in blue

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Table of Contents

1 DEFINITION OF TERMS AND LIST OF ABBREVIATIONS ................................... 10
2 EXECUTIVE SUMMARY ............................................................................................ 11
Background ............................................................................................................................. 11
Objectives ................................................................................................................................ 11
Methods ................................................................................................................................... 12
Results ..................................................................................................................................... 13
Conclusions ............................................................................................................................. 20
3. BACKGROUND AND DEFINITION OF THE DECISION PROBLEM ......................... 21
3.1 Condition and aetiology .................................................................................................... 21
3.1.1 Background .................................................................................................................... 21
3.1.2 Awareness symptoms and sequelae ................................................................................ 21
3.1.3 Incidence of intraoperative awareness ............................................................................ 22
3.1.4 Risk factors for intraoperative awareness ....................................................................... 23
3.1.5 Impact of intraoperative awareness ................................................................................ 24
3.1.6 Measurement of intraoperative awareness ..................................................................... 24
3.1.7 Consequences of anaesthesia overdose .......................................................................... 25
3.2 Description of technologies under assessment .................................................................. 26
3.2.1 Bispectral Index (BIS) (Covidien) .................................................................................. 27
3.2.2 E-Entropy module (GE Healthcare) ............................................................................... 27
3.2.3 Narcotrend (Narcotrend) ................................................................................................ 28
3.2.4 Subgroups of patients ..................................................................................................... 28
3.2.5 Artefacts ......................................................................................................................... 29
3.2.6 Current usage in the UK ................................................................................................. 29
3.2.7 Training .......................................................................................................................... 30
3.3 Comparators ...................................................................................................................... 30
3.4 Care pathways ................................................................................................................... 31
3.5 Summary of the decision problem ..................................................................................... 31
4. ASSESSMENT METHODS ............................................................................................... 33
4.1 Systematic review of patient outcomes ............................................................................. 33
4.1.1 Identification of studies .................................................................................................. 33
4.1.2 Inclusion/exclusion criteria ............................................................................................ 34
4.1.3 Data extraction and critical appraisal methods ............................................................... 36
4.2 Systematic review of cost-effectiveness ............................................................................ 37
4.2.1 Identification of studies .................................................................................................. 37
4.2.2 Inclusion/exclusion criteria ............................................................................................ 37
4.2.3 Data extraction and critical appraisal methods ............................................................... 38
4.2.4 Method of data synthesis ................................................................................................ 38
4.3 Economic evaluation ......................................................................................................... 38
5. ASSESSMENT RESULTS ................................................................................................. 40
5.1 Results of systematic review of patient outcomes ............................................................. 40
5.1.1 Quantity and quality of research available ..................................................................... 40
5.1.2 Characteristics of included studies - BIS ........................................................................ 49
5.1.3 Assessment of outcomes – BIS ...................................................................................... 58
5.1.4 Characteristics of included studies – Entropy ............................................................... 71
5.1.5 Assessment of outcomes – Entropy ................................................................................ 77
5.1.6 Characteristics of included studies - Narcotrend ............................................................ 85
5.1.7 Assessment of outcomes – Narcotrend ........................................................................... 87
5.2 Results of systematic review of cost-effectiveness ........................................................... 92
5.2.1 Quantity and quality of research available ..................................................................... 92
5.2.2 Characteristics and results of included studies ............................................................... 94
5.2.3 Summary ........................................................................................................................ 95
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5.3 Model structure, model parameterisation and results of economic evaluation.................. 95
5.3.1 Description of decision analytic model .......................................................................... 95
5.3.2 Model parameters ........................................................................................................... 97
5.3.3 Model Results .............................................................................................................. 131
6. ASSESSMENT OF FACTORS RELEVANT TO THE NHS AND ................................. 187
OTHER PARTIES ................................................................................................................ 187
7. DISCUSSION ................................................................................................................... 189
7.1 Statement of principal findings ....................................................................................... 189
7.1.1 Systematic review of patient outcomes ........................................................................ 189
7.1.2 Economic evaluation .................................................................................................... 199
7.2 Strengths and limitations of the assessment .................................................................... 207
7.3 Uncertainties .................................................................................................................... 211
8. CONCLUSIONS ............................................................................................................... 214
Implications for service provision ......................................................................................... 215
Suggested research priorities ................................................................................................. 215
9. REFERENCES .................................................................................................................. 217
10. APPENDICES ................................................................................................................. 233
Appendix 1: Report methods for synthesis of evidence of clinical and cost-effectiveness as
described in the research protocol ......................................................................................... 233
Appendix 2: Literature search strategies ............................................................................... 237
Appendix 3: Inclusion/exclusion worksheet used in systematic review of patient outcomes 241
Appendix 4: Reasons for the exclusion of full-text publications from systematic review of
patient outcomes .................................................................................................................... 243
Appendix 5: Data extraction and critical appraisal forms used in the systematic review of
patient outcomes .................................................................................................................... 244
Appendix 6: Data extraction and critical appraisal forms used in the ................................... 325
systematic review of cost-effectiveness ................................................................................ 325
Appendix 7: Studies excluded from the review of economic evaluations ............................. 333
Appendix 8: Pooled intravenous anaesthetic consumption for Narcotrend RCTs ................ 334
Appendix 9: Derivation of the pooled estimates of cumulative incidence of awareness used in
the model ............................................................................................................................... 336
Appendix 10: Survival modelling methodology ................................................................... 339
Appendix 11: Search strategy to identify utility values for PTSD ........................................ 341
Appendix 12: Ongoing trials identified ................................................................................. 343

Tables

Table 1 - Estimates of the incidence of intraoperative awareness from studies with large
sample sizes ............................................................................................................................. 22
Table 2 Inclusion/ exclusion criteria for screening titles and abstracts ................................... 37
Table 3– Distribution of diagnostic technologies across the trials included in this review ..... 42
Table 4- Summary of Risk of Bias - BIS ................................................................................ 43
Table 5 - Summary of Risk of Bias - Entropy ......................................................................... 45
Table 6 - Summary of Risk of Bias - Narcotrend .................................................................... 48
Table 7 - BIS study outcomes ................................................................................................. 55
Table 8 - Intraoperative awareness during BIS monitoring (all patients, irrespective of risk of
awareness) ............................................................................................................................... 59
Table 9 – Consumption of anaesthetic during BIS monitoring ............................................... 62
Table 10 - Post-Anaesthesia Care Unit (PACU) stay outcomes following BIS monitoring ... 65
Table 11 - Time to extubation following BIS monitoring ....................................................... 66
Table 12 – Time to eye opening following BIS monitoring .................................................... 67
Table 13 -Time to other recovery outcomes ............................................................................ 68
Table 14 – Mortality, myocardial infarction and stroke .......................................................... 69
Table 15 - Entropy study outcomes ......................................................................................... 76
Table 16 – Intraoperative awareness during entropy monitoring ............................................ 78
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Table 17 – Consumption of anaesthetic during entropy monitoring ....................................... 79
Table 18 - Time to recovery from anaesthesia (before discharge to PACU) .......................... 80
Table 19 - Time for discharge to/from PACU ......................................................................... 82
Table 20 – Post-operative pain ................................................................................................ 82
Table 21 – Analgesic consumption during entropy monitoring .............................................. 83
Table 22 – Post-operative nausea and vomiting ...................................................................... 83
Table 23 - Narcotrend study outcomes .................................................................................... 87
Table 24 - Anaesthetic consumption ....................................................................................... 88
Table 25 - Time to arrival at post-anaesthetic care unit. ......................................................... 89
Table 26 - Time to eye opening ............................................................................................... 89
Table 27 - Time to extubation ................................................................................................. 90
Table 28 - Time to emergence from anaesthesia ..................................................................... 90
Table 29 - Critical appraisal checklist of economic evaluation (Questions in this checklist
based on Philips and colleagues) ............................................................................................. 93
Table 30 - Characteristics of included economic evaluations ................................................. 94
Table 31 - Costs of DoA modules ........................................................................................... 97
Table 32 - Equivalent annual costs of DoA modules .............................................................. 98
Table 33 - Mean total and variable costs, by anaesthetic regime, reported for CESA RCT . 100
Table 34 - Estimated consumption of inhaled anaesthetic agents, ml per MAC hour .......... 100
Table 35 - Change in anaesthetic usage associated with depth of anaesthesia monitoring –
mean difference and 95% confidence interval ...................................................................... 101
Table 36 – Unit costs of general anaesthetics........................................................................ 102
Table 37 - Estimated baseline cost, estimated change in consumption and cost of anaesthetic
associated with depth of anaesthesia monitoring .................................................................. 103
Table 38 - Estimated odds ratios for POCD at seven days and three months estimated from
Chan et al ............................................................................................................................... 105
Table 39 - Studies reporting incidence of awareness in general surgical and high-risk
populations – summary of characteristics, methods and results ............................................ 107
Table 40 - Effectiveness of depth of anaesthesia monitoring on risk of awareness – Peto Odds
Ratio and 95% confidence interval from systematic review of patient outcomes ................. 109
Table 41 - Studies reporting incidence of late psychological symptoms and PTSD in patients
who experienced awareness - summary of characteristics, methods and results................... 111
Table 42 - Baseline values for probability of LPS and PTSD in patients experiencing
awareness............................................................................................................................... 114
Table 43 - Inclusion criteria for quality of life review .......................................................... 116
Table 44 - Characteristics of included QoL studies .............................................................. 117
Table 45 - Utility scores reported in the included QoL studies ............................................. 119
Table 46 - Health related utilities estimated from SF-36 scores ........................................... 120
Table 47 - Unit cost and treatment uptake assumptions used to calculate costs of managing
PTSD ..................................................................................................................................... 123
Table 48 - Model input parameters. Cost per patient of depth of anaesthesia modules ........ 125
Table 49 - Model input parameters. Anaesthetic drug consumption ..................................... 126
Table 50 - Model input parameters. Intra-operative awareness ............................................ 128
Table 51 - Model input parameters. Post-operative complication (PONV and POCD) ........ 130
Table 52 - Cost effectiveness of BIS compared with standard clinical monitoring in a
population at high risk of awareness, undergoing TIVA ....................................................... 131
Table 53 - Breakdown of total cost for standard clinical monitoring and BIS for patients at
high risk of awareness, undergoing TIVA ............................................................................ 132
Table 54 - Cost effectiveness of BIS compared with standard clinical monitoring in a general
surgical population, undergoing TIVA .................................................................................. 132
Table 55 - Breakdown of total cost for standard clinical monitoring and BIS for a general
surgical population, undergoing TIVA .................................................................................. 133
Table 56 - Cost effectiveness of BIS compared with standard clinical monitoring in a
population at high risk of awareness undergoing mixed anaesthesia .................................... 133
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Table 57 - Breakdown of total cost for standard clinical monitoring and BIS in patients at
high risk of awareness undergoing mixed anaesthesia .......................................................... 134
Table 58 - Cost effectiveness of depth of anaesthesia monitoring with BIS compared with
standard clinical monitoring in a general population undergoing mixed anesthesia ............. 134
Table 59 - Breakdown of total cost for standard clinical monitoring and BIS for a general
surgical population, undergoing mixed anaesthesia .............................................................. 135
Table 60 – One-way sensitivity analysis: BIS compared with standard clinical monitoring in
patients at high risk of awareness undergoing TIVA ............................................................ 136
Table 61 - One way sensitivity analysis: BIS compared with standard clinical monitoring in a
general surgical population, undergoing TIVA ..................................................................... 137
Table 62 - One way sensitivity analysis: BIS compared with standard clinical monitoring
patients at high risk of awareness undergoing mixed general anaesthesia ............................ 139
Table 63 - One way sensitivity analysis: BIS compared with standard clinical monitoring in a
general surgical population undergoing mixed general anaesthesia ...................................... 140
Table 64 - Scenario analysis: including an estimated effect of BIS monitoring on incidence of
PONV in patients at high risk of awareness undergoing TIVA ............................................ 141
Table 65 - Scenario analysis: including an estimated effect of BIS monitoring on incidence of
PONV in a general surgical population undergoing TIVA ................................................... 142
Table 66 - Scenario analysis: including an estimated effect of BIS monitoring on incidence of
PONV in patients at high risk of awareness undergoing mixed anaesthesia ......................... 142
Table 67 - Scenario analysis: including an estimated effect of BIS monitoring on incidence of
PONV in a general surgical population undergoing mixed anaesthesia ................................ 143
Table 68 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
BIS monitoring for patients at high risk of awareness .......................................................... 144
Table 69 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
BIS monitoring for a general surgical population undergoing TIVA .................................... 145
Table 70 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
BIS monitoring for a general surgical population undergoing mixed general anaesthesia ... 145
Table 71 – Scenario analysis: impact of number of patients per device year on cost
effectiveness of BIS monitoring in patients undergoing TIVA ............................................. 146
Table 72 – Scenario analysis: impact of number of patients per device year on cost
effectiveness of BIS monitoring in patients undergoing mixed anaesthesia ......................... 146
Table 73 - Scenario analysis: impact of utility decrement for PTSD on cost effectiveness of
BIS in patients at high risk of awareness undergoing TIVA or mixed anaesthesia............... 147
Table 74 - Scenario analysis: impact of utility decrement for PTSD cost effectiveness of BIS
in a general surgical population undergoing TIVA or mixed anaesthesia ............................. 148
Table 75 - Cost effectiveness of Entropy compared with standard clinical monitoring in a
population at high risk of awareness, undergoing TIVA ....................................................... 149
Table 76 - Breakdown of total cost for standard clinical monitoring and Entropy in patients at
high risk of awareness, undergoing TIVA ............................................................................ 150
Table 77 - Cost effectiveness of Entropy compared with standard clinical monitoring in a
general surgical population undergoing TIVA (drug use based on Ellerkman et al) ............ 150
Table 78 - Cost effectiveness of Entropy compared with standard clinical monitoring in a
general surgical population undergoing TIVA (drug use based on Gruenewald et al) ......... 151
Table 79 - Breakdown of total cost for standard clinical monitoring and Entropy in a general
surgical population, undergoing TIVA .................................................................................. 151
Table 80 - Cost effectiveness of Entropy compared with standard clinical monitoring in a
population at high risk of awareness undergoing mixed anaesthesia .................................... 152
Table 81 - Breakdown of total cost for standard clinical monitoring and Entropy in a
population at high risk of awareness, undergoing mixed anaesthesia ................................... 152
Table 82 - Cost effectiveness of Entropy compared with standard clinical monitoring in a
general surgical population undergoing mixed anaesthesia .................................................. 153
Table 83 - Breakdown of total cost for standard clinical monitoring and Entropy in a general
surgical population undergoing mixed anaesthesia ............................................................... 153
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Table 84 - One way sensitivity analysis: Entropy compared with standard clinical monitoring
in patients at high risk of awareness, undergoing TIVA ....................................................... 154
Table 85 - One way sensitivity analysis: Entropy compared with standard clinical monitoring
in a general surgical population, undergoing TIVA (drug use based on Ellerkman et al) .... 156
Table 86 - One way sensitivity analysis: Entropy compared with standard clinical monitoring
in a general surgical population, undergoing TIVA (drug use based on Gruenewald et al) . 157
Table 87 - One way sensitivity analysis: Entropy compared with standard clinical monitoring
in patients at high risk of awareness, undergoing mixed anaesthesia.................................... 159
Table 88 - One way sensitivity analysis: Entropy compared with standard clinical monitoring
in a general surgical population, undergoing mixed anaesthesia .......................................... 160
Table 89 - Scenario analysis: including an estimated effect of Entropy monitoring on the
incidence of PONV in patients at high risk of awareness undergoing TIVA ........................ 161
Table 90 - Scenario analysis: including an estimated effect of Entropy monitoring on the
incidence of PONV in a general surgical population undergoing TIVA ............................... 162
Table 91 - Scenario analysis: including an estimated effect of Entropy monitoring on
incidence of PONV in patients at high risk of awareness undergoing mixed anaesthesia .... 163
Table 92 - Scenario analysis: including an estimated effect of Entropy monitoring on
incidence of PONV in a general surgical population, undergoing mixed anaesthesia .......... 163
Table 93 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Entropy monitoring for patients at high risk of awareness .................................................... 164
Table 94 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Entropy monitoring in a general surgical population undergoing TIVA .............................. 165
Table 95 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Entropy monitoring in a general surgical population undergoing mixed anaesthesia ........... 166
Table 96 – Scenario analysis: impact of number of patients per device year on cost
effectiveness of Entropy monitoring in a general surgical population .................................. 167
Table 97 - Scenario analysis: impact of utility decrement for PTSD on cost effectiveness of
Entropy in patients at high risk of awareness undergoing TIVA or mixed anaesthesia ........ 168
Table 98 - Scenario analysis: impact of utility decrement for PTSD on cost effectiveness of
Entropy in a general surgical population undergoing TIVA or mixed anaesthesia .............. 169
Table 99 - Cost effectiveness of Narcotrend compared with standard clinical monitoring in a
population at high risk of awareness, undergoing TIVA ....................................................... 170
Table 100 - Breakdown of total cost for standard clinical monitoring and Narcotrend for
patients at high risk of awareness, undergoing TIVA ........................................................... 171
Table 101 - Cost effectiveness of Narcotrend compared with standard clinical monitoring in a
general surgical population, undergoing TIVA ..................................................................... 171
Table 102 - Breakdown of total cost for standard clinical monitoring and Narcotrend in a
general surgical population, undergoing TIVA ..................................................................... 172
Table 103 - Cost effectiveness of Narcotrend compared with standard clinical monitoring in a
high-risk population, undergoing mixed anaesthesia ............................................................ 172
Table 104 - Breakdown of total cost for standard clinical monitoring and Narcotrend in
patients at high risk of awareness undergoing mixed anaesthesia ......................................... 173
Table 105 - Cost effectiveness of Narcotrend compared with standard clinical monitoring in a
general surgical population undergoing mixed anaesthesia .................................................. 173
Table 106 - Breakdown of total cost for standard clinical monitoring and Narcotrend for a
general surgical population undergoing mixed anaesthesia .................................................. 174
Table 107 - One way sensitivity analysis: Narcotrend compared with standard clinical
monitoring in patients at high risk of awareness undergoing TIVA ..................................... 175
Table 108 - One way sensitivity analysis: Narcotrend compared with standard clinical
monitoring in a general surgical population undergoing TIVA ............................................ 176
Table 109 - One way sensitivity analysis: Nacrotrend compared with standard clinical
monitoring in patients at high risk of awareness undergoing mixed anaesthesia .................. 177
Table 110 - One way sensitivity analysis: Narcotrend compared with standard clinical
monitoring in a general surgical population undergoing mixed anaesthesia ......................... 178
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Table 111 - Scenario analysis: including an estimated effect of Narcotrend monitoring on the
incidence of PONV in patients at high risk of awareness undergoing h TIVA ..................... 179
Table 112 - Scenario analysis: including an estimated effect of Narcotrend monitoring on the
incidence of PONV in a general surgical population undergoing TIVA ............................... 180
Table 113 - Scenario analysis: including an estimated effect of Narcotrend on the incidence of
PONV in patients at high risk of awareness undergoing mixed anaesthesia ......................... 180
Table 114 - Scenario analysis: including an estimated effect of Narcotrend on the incidence of
PONV in a general surgical population undergoing mixed anaesthesia ................................ 181
Table 115 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Narcotrend monitoring for patients at high risk of awareness ............................................... 182
Table 116 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Narcotrend monitoring for a general surgical population, undergoing TIVA ....................... 182
Table 117 - Scenario analysis: impact of baseline risk of awareness on cost effectiveness of
Narcotrend monitoring for a general surgical population, undergoing mixed anaesthesia ... 183
Table 118 – Scenario analysis: impact of number of patients per device year on cost
effectiveness of Narcotrend monitoring in general surgical patients .................................... 184
Table 119 - Scenario analysis: impact of utility decrement for PTSD on cost effectiveness of
Narcotrend in patients at high risk of awareness undergoing TIVA or mixed anaesthesia ... 185
Table 120 - Scenario analysis: impact of utility decrement for PTSD on cost effectiveness of
Narcotrend in general surgical population undergoing TIVA or mixed anaesthesia ............ 186
Table 121 Propofol consumption in RCTs using Narcotrend depth of anaesthesia monitoring
............................................................................................................................................... 334
Table 122 Pooled estimates for reduction in propofol consumption in RCTs using Narcotrend
depth of anaesthesia monitoring ............................................................................................ 334
Table 123 Remifentanil consumption in RCTs using Narcotrend depth of anaesthesia
monitoring ............................................................................................................................. 335
Table 124 Pooled estimates for reduction in remifentanil consumption in RCTs using
Narcotrend depth of anaesthesia monitoring ......................................................................... 335

Figures

Figure 1 - PRISMA flow chart showing the study selection process for bibliographic records
(excluding those already identified in a Cochrane systematic review of BIS studies) ............ 40
Figure 2 – Meta-analysis of intraoperative awareness during BIS monitoring (patients
classified at higher risk of awareness) ..................................................................................... 60
Figure 3– Meta-analysis of volatile anaesthetic consumption (sevoflurane) during BIS
monitoring, MAC equivalents ................................................................................................. 63
Figure 4 – Meta-analysis of propofol consumption during BIS monitoring, mg/kg/min ........ 63
Figure 5 Flow chart of identification of studies for inclusion in the review of cost
effectiveness ............................................................................................................................ 92
Figure 6 - Decision tree evaluating cost effectiveness of depth of anaesthesia monitoring
compared with standard clinical monitoring ........................................................................... 96
Figure 7 - Survival curve based on duration of symptoms for respondents who did not seek
treatment for PTSD, reported by Kessler and colleagues and fitted Weibull model ............. 115
Figure 8 - Flow chart of identification of QoL studies for inclusion in the review ............... 116
Figure 9 - Care pathways and costing assumptions developed for NICE ............................. 122
Figure 10 Forest plot for the pooled estimate of the mean difference in propofol consumption
using Narcotrend depth of anaesthesia monitoring compared with standard clinical monitoring
............................................................................................................................................... 334
Figure 11 Forest plot for the pooled estimate of the mean difference in remifentanil
consumption using Narcotrend depth of anaesthesia monitoring compared with standard
clinical monitoring ................................................................................................................ 335
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1 DEFINITION OF TERMS AND LIST OF ABBREVIATIONS

Technical terms and abbreviations are used throughout this report. The meaning is usually
clear from the context, but a glossary is provided for the non-specialist reader.

Term Definition
ASA American Society of Anesthesiologists
BAG-RECALL BIS or Anesthetic Gas to Reduce Explicit Recall
BIS Bispectral Index
BNF British National Formulary
CI Confidence interval
ECG Electrocardiogram
EEG Electroencephalography
ETAC End-tidal anaesthetic concentration
FGF Fresh Gas Flow
GA General anaesthesia
HRQoL Health Related Quality of Life
ICER Incremental Cost-effectiveness Ratio
ITT Intention to treat
LPS Late psychological symptoms
MAC Minimum Alveolar Concentration (MAC)
NICE National Institute for Health and Clinical Excellence
NR Not Reported
NS Not statistically significant
PACU Post Anaesthesia Care Unit (PACU)
POCD Post-operative cognitive dysfunction
PONV Post-Operative Nausea and Vomiting
PTSD Post-Traumatic Stress Disorder
QoL Quality of Life
QALY Quality Adjusted Life Year
RCT Randomised Controlled Trial
TIVA Total intravenous anaesthesia
TTO Time Trade Off
SG Standard Gamble

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