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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
The Influence of Anaesthetic Depth on Patient Outcome after Major Surgery
Scientific title
A prospective, randomised, double-blind, active control, parallel assessment, intention to treat, safety and efficacy study comparing "light" and "deep" general anesthesia monitored with Bispectral Index (BIS) to investigate whether depth of anesthesia alters peri-operative outcomes in patients having major surgery
Secondary ID [1] 280655 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Perioperative Outcomes 286661 0
Condition category
Condition code
Anaesthesiology 286955 286955 0 0
Other anaesthesiology

Study type
Description of intervention(s) / exposure
General anaesthesia monitored with Bispectral Index (BIS). BIS targets will be either 50 or 35. We expect 90% of anaesthesia time to be within 5 units of the target range and no deviations for >5 minutes. Anaesthesia standard care using standard anaesthetic hypnotics, volatiles, opioids and relaxants, intravenous or inhalational gas induction, volatile maintenance, continuous BIS monitoring, computerised data logging of BIS, blood pressure and volatile anaesthetic concentration. An individualised blood pressure target range appropriate for the patient being studied will be set by the anaesthetist before BIS target randomization
Intervention code [1] 285044 0
Treatment: Other
Intervention code [2] 285062 0
Early detection / Screening
Intervention code [3] 285063 0
Treatment: Drugs
Comparator / control treatment
Comparison between BIS target of 50 and 35 will be the comparable treatment
Control group
Dose comparison

Primary outcome [1] 287299 0
One-year mortality. One year mortality will be compared between randomised groups using a Mantel-Haenszel Chi-square test, stratified on study centre.
A two-tailed p-value <0.049 will be taken to indicate statistical significance.
One year mortality is expected to be approximately 10% based on the findings of Leslie's study and Australasian studies. The reduction in mortality in the light anaesthesia group is expected to be 20%.
A power analysis using p1=0.10 and p2=0.08 indicates that N=3250 patients are required in each group, Beta=0.8,alpha=0.049. The alpha level is reduced to allow for the single interim analysis.
Timepoint [1] 287299 0
one year after randomisation
Secondary outcome [1] 297858 0
Morbidity review for the presence of myocardial infarction (MI), cardiac arrest, pulmonary embolism (PE), stroke, sepsis, surgical site infection, Intensive Care Unit (ICU) stay, hospital stay, awareness, WHODAS disability score, disability free survival, persistent postoperative pain and cancer recurrence will be compared between randomized groups using Mantel-Haenszel chi-square tests or Fisher's exact test depending on the expected cell frequencies. Additionally a composite score including the presence of any of MI, cardiac arrest, stroke, PE, sepsis and surgical site infection, will be compared between randomised groups also using a chi-square test. Additional analyses will also explore the role of MI, cardiac arrest, stroke, PE, sepsis and surgical site infection on one year mortality using Cox's proportional hazards regression to develop a model of independent predictors of one year mortality. The randomized group will be added to this model to assist explanation of any observed differences in outcome between the randomized groups.
Timepoint [1] 297858 0
30 days and one year randomisation

Key inclusion criteria
Age equal to/greater than 60 years, ASA grade 3 or 4, surgery expected to last >2 hours, post-operative hospital stay expected to be 2 or more nights, general anaesthesia with or without major regional block.
Minimum age
60 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Unable to monitor BIS (eg cranial or intracranial surgery), not expected to survive one year, unable to consent, not expected to be contactable in one year, surgery with ‘wake-up’ test.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Patients who are eligible for the trial will be identified by a consultant anesthetist and given the trial information sheet by a member of the research team and encouraged to discuss the study with their family or whanau before written informed consent is sought.
Treatment allocation
Once all entry details are given and eligibility confirmed, the patient will be randomised by contacting the automated central telephone randomisation service. Allocation will be concealed from subjects, investigators and outcome assessors. Only the anesthetist conducting the anesthesia will be aware of the treatment allocation.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table generated by a computer software - sequence. Assignment to one of the two groups will be stratified for collaborating centre and a unique study number given.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

The people assessing the outcomes
Intervention assignment
Other design features
Phase 3
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 1059 0
Austin Health - Austin Hospital - Heidelberg
Recruitment hospital [2] 1060 0
St Vincents Private Hospital Lismore - Lismore
Recruitment hospital [3] 1061 0
Royal Melbourne Hospital - City campus - Parkville
Recruitment hospital [4] 1062 0
The Alfred - Prahran
Recruitment hospital [5] 1063 0
Western Hospital - Henley Beach
Recruitment hospital [6] 1064 0
Royal Perth Hospital - Perth
Recruitment hospital [7] 1065 0
Fremantle Hospital and Health Service - Fremantle
Recruitment hospital [8] 6072 0
Prince of Wales Hospital - Randwick
Recruitment hospital [9] 6073 0
Monash Medical Centre - Clayton campus - Clayton
Recruitment hospital [10] 6074 0
Peter MacCallum Cancer Institute - East Melbourne
Recruitment hospital [11] 6075 0
Barwon Health - Geelong Hospital campus - Geelong
Recruitment hospital [12] 6076 0
Westmead Hospital - Westmead
Recruitment hospital [13] 6077 0
St John of God Hospital, Ballarat - Ballarat
Recruitment hospital [14] 6078 0
St John of God Hospital, Subiaco - Subiaco
Recruitment hospital [15] 6079 0
Royal Hobart Hospital - Hobart
Recruitment hospital [16] 6080 0
Liverpool Hospital - Liverpool
Recruitment hospital [17] 6081 0
The Royal Adelaide Hospital - Adelaide
Recruitment hospital [18] 6082 0
King Edward Memorial Hospital - Subiaco
Recruitment hospital [19] 6083 0
The Canberra Hospital - Garran
Recruitment hospital [20] 6084 0
Epworth Richmond - Richmond
Recruitment hospital [21] 6085 0
Nambour General Hospital - Nambour
Recruitment hospital [22] 6086 0
Royal Brisbane & Womens Hospital - Herston
Recruitment hospital [23] 6087 0
Fiona Stanley Hospital - Murdoch
Recruitment outside Australia
Country [1] 4357 0
New Zealand
State/province [1] 4357 0
Country [2] 5116 0
Hong Kong
State/province [2] 5116 0
Shantin, New Territories
Country [3] 7993 0
United States of America
State/province [3] 7993 0
Country [4] 7994 0
United States of America
State/province [4] 7994 0
New York
Country [5] 7995 0
United States of America
State/province [5] 7995 0
Country [6] 7996 0
United States of America
State/province [6] 7996 0
North Carolina
Country [7] 7997 0
United Kingdom
State/province [7] 7997 0
Country [8] 7998 0
State/province [8] 7998 0

Funding & Sponsors
Funding source category [1] 285411 0
Government body
Name [1] 285411 0
Health Research Council of new Zealand
Address [1] 285411 0
Level 3 - ProCARE Building, Grafton Mews, at 110 Stanley Street, Auckland 1010
Country [1] 285411 0
New Zealand
Funding source category [2] 287364 0
Government body
Name [2] 287364 0
National Health and Medical Research Council
Address [2] 287364 0
Level 1, 16 Marcus Clarke Street,
ACT 2601
Country [2] 287364 0
Primary sponsor type
Assoc Professor Dr Timothy Short
Department of Anaesthesia
Level 8, Support Building
Auckland City Hospital
Park Rd
Auckland 1023
New Zealand
Secondary sponsor category [1] 292794 0
Name [1] 292794 0
Address [1] 292794 0
Country [1] 292794 0
Other collaborator category [1] 276856 0
Other Collaborative groups
Name [1] 276856 0
Australia New Zealand College of Anaesthetist Clinical Trials Group
Address [1] 276856 0
630 St Kilda Road
Melbourne Vic 3004
Country [1] 276856 0
Other collaborator category [2] 277437 0
Name [2] 277437 0
Monash University
Address [2] 277437 0
School of Public Health and Preventive Medicine
The Alfred Centre
99 Commercial Road
Melbourne Vic 3004
Country [2] 277437 0

Ethics approval
Ethics application status
Ethics committee name [1] 287425 0
Northern A Health and Disability Ethics Committee
Ethics committee address [1] 287425 0
Health and Disability Ethics Committees
Ministry of Health
1 the Terrace
PO Box 5013
Ethics committee country [1] 287425 0
New Zealand
Date submitted for ethics approval [1] 287425 0
Approval date [1] 287425 0
Ethics approval number [1] 287425 0
Ethics committee name [2] 295395 0
Melbourne Health Human Research Ethics Committee
Ethics committee address [2] 295395 0
Royal Melbourne Hospital
Office for Research
Level 6
300 Grattan Street
Victoria 3050
Ethics committee country [2] 295395 0
Date submitted for ethics approval [2] 295395 0
Approval date [2] 295395 0
Ethics approval number [2] 295395 0

Brief summary
Approximately 450,000 people undergo surgery for various reasons in New Zealand. Most of these people are given general anaesthesia for their procedure. We use a range of monitoring to assess vital signs and other safety factors. One of the monitoring systems we use is the Bi-spectral Index (BIS), which uses electroencephalogram (EEG) waves to determine the depth (how deeply anaesthetised) patients are during their procedure. These monitoring systems are widely available nationally and internationally, however, the optimal depth at which anaesthetics should be given is unknown. Recent observational studies have shown a 20% increase in mortality in patients undergoing major surgery who receive relatively deep anaesthesia. We plan to perform a large scale randomized trial investigating the difference between two clinically standard depth ranges, which are commonly referred to “light” and “deep” anaesthesia, to definitively answer the question of whether anaesthetic depth alters surgical outcome. In particular we will look at death rate at one year and also whether there are differences in other complications of surgery and anaesthesia, including wound infection, cardiovascular and neurological complications, pain and awareness
Trial website
Trial related presentations / publications
Public notes
Attachments [1] 2206 2206 0 0

Principal investigator
Name 34290 0
A/Prof Timothy Short
Address 34290 0
Dept Adult and Trauma Anaesthesia
Level 8, Support Building
Auckland City Hospital
2 Park Road
Auckland 1023
Country 34290 0
New Zealand
Phone 34290 0
+64 9 3074949 extn 25720
Fax 34290 0
+64 9 3754378
Email 34290 0
Contact person for public queries
Name 17537 0
Ms Davina McAllister
Address 17537 0
Anaesthesia Research
Department of Anaesthesia and Perioperative Medicine
Level 8, Support Building
Auckland City Hospital
Park Rd
Auckland 1023
Country 17537 0
New Zealand
Phone 17537 0
Fax 17537 0
Email 17537 0
Contact person for scientific queries
Name 8465 0
A/Prof Timothy Short
Address 8465 0
Anaesthesia Research
Department of Anaesthesia and Perioperative Medicine
Level 8, Support Building
Auckland City Hospital
Park Rd
Auckland 1023
Country 8465 0
New Zealand
Phone 8465 0
Fax 8465 0
Email 8465 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
What supporting documents are/will be available?
Summary results
Have study results been published in a peer-reviewed journal?
Journal publication details
Publication date and citation/details [1] 6748 0 Published online October 20, 2019
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary