Post-Operative ConfusionBALANCEDLTNCT04965324
Depth of Anaesthesia and Long-term Survival: The Balanced Anaesthesia Follow-up Study
An observational study of Post-Operative Confusion and Long Term Adverse Effects, run by Auckland City Hospital at 1 site in New Zealand.
Trial summary
Anaesthetic depth and complications after major surgery: an international, randomised controlled trial - The BALANCED trial. In this large, international, randomised controlled trial that enrolled patients aged 60 years and over with significant comorbidity and at increased risk of complications after major surgery… Read more about this study
- Who is it for?
- Ages 60 years and older
- Conditions the study is for
- Post-Operative Confusion, Long Term Adverse Effects, Surgery--Complications
- What is being tested?
- Anaesthesia Depth
- How many people
- 6,644 participants
- Where
- 1 siteNew Zealand
- Study dates
- 19 Dec 2012to 31 Aug 2026
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 60 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: All participants who were recruited to the BALANCED Trial and who met the inclusion and no exclusion criteria for analysis of the long term outcome.
Who may be able to join
- Age over 60 years and over
- ASA physical status 3 or 4
- Surgery expected to last over 2 hours
- Hospital length of stay expected to be 2 nights or more
- General anaesthesia with or without major regional block
- Able to monitor BIS throughout anaesthesia
Who cannot join
- Unable to monitor BIS
- Unable to consent
- Surgery with 'wake up' test
- Propofol infusion for part or all of maintenance of anaesthesia
- Previous enrolment in Balanced study
- Exclusion The intention-to-treat (ITT) population is defined as all randomised participants who met the inclusion and exclusion criteria who had surgery.
- The per-protocol (PP) population is defined as all randomised participants in the study who meet all the inclusion/exclusion criteria for BALANCED with BIS group classified according to the actual median BIS value achieved irrespective of randomisation.
- Participants were allocated to the BIS=50 group if the achieved median BIS is between 45 and 55 inclusive, and to the BIS=35 group if the achieved median BIS is between 30 and 40 inclusive. Participants who are not within these ranges will be excluded from these analyses.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Depth of Anaesthesia and Long-term Survival in Elderly Surgical Patients: The Balanced Anaesthesia Study Long-term Follow-up Study
Anaesthetic depth and complications after major surgery: an international, randomised controlled trial - The BALANCED trial.
In this large, international, randomised controlled trial that enrolled patients aged 60 years and over with significant comorbidity and at increased risk of complications after major surgery, we found no evidence that light general anaesthesia (bispectral index 50) was superior to deep general anaesthesia (bispectral index 35) in reducing 1-year mortality. The BALANCED long term follow up study will look at whether depth of anesthesia affects long term (beyond 1 year) survival.
Read more
The primary hypothesis is that targetting BIS 50 will result in superior long term survival compared to targetting BIS 35.
The two secondary hypotheses are that BIS titration to BIS 50 will
- reduce local cancer recurrence or metastatic spread and consequently improve long-term survival
- reduce postoperative delirium and associated cognitive impairment and consequently improve long-term survival
Both these mechanisms would be expected to take longer to manifest as reduced survival than 1-year all-cause mortality primary outcome in the Balanced trial. Trials of cancer outcomes often use 5-year survival or similar timeframes to determine evidence of clinical benefit. A steeper cognitive trajectory due to intermediate outcomes such as delirium and cognitive impairment may take longer than 1 year to produce a clinically important difference in survival 30. The 10.6% relative risk reduction seen in the Balanced trial could translate to a statistically and clinically meaningful survival difference in this high-risk population. This population may have 5-year survival of ~80% translating to an absolute survival difference of ~2% potentially (if the ~10% RRR is maintained beyond 1 year). The alternative is that there is no long-term mortality difference which would provide continuing clinical guidance of the safety of current practice in patients who are not at high risk of delirium. This study could provide a rationale for trials in larger populations (such as the total Balanced trial population) or targeted subgroups such as cancer and delirium to provide further mechanistic insights.
Long-term survival is an important patient-centred outcome. The mechanisms described above may manifest in longer-term outcomes providing a clear rationale for the current trial.
- Conditions
- Post-Operative Confusion, Long Term Adverse Effects, Surgery--Complications, Cognitive Dysfunction, Postoperative
- Being tested
- Anaesthesia Depth
- Keywords
- Anesthesia, Delirium, Incidence, Long Term Survival
- Medical subject headings
- Long Term Adverse Effects, Postoperative Cognitive Complications, Delirium
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Anaesthesia DepthOther
| Study group | Role | What they receive |
|---|---|---|
| Anaesthesia Depth BIS 35 | BIS 35 Receives: Other: Anaesthesia Depth | |
| Anaesthesia Depth BIS 50 | BIS 50 Receives: Other: Anaesthesia Depth |
What is being measured
The primary outcome is the main question the study is designed to answer.
Survival
Survival
Measured: Between one year and eight years after randomization to the BALANCED Trial
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Jul 2021
- Study start19 Dec 2012
- Primary completion30 Jun 2026 (estimated)
- Study completion31 Aug 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Post-Operative ConfusionStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 6,644 participants (actual)
Sponsor and investigators
- Lead sponsor
- Auckland City Hospital
- Sponsor type
- Other government
- Collaborators
- Health Research Council, New Zealand, Australian and New Zealand College of Anaesthetists
- Responsible party
- Sponsor
- Investigators
- Timothy Dr Short, Principal investigator, Auckland City Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04965324
- Sponsor's protocol ID
- A+9283
- Other IDs
- ACTRN12612000632897
- Acronym
- BALANCEDLT
- Status last verified
- Apr 2026
- First submitted
- 7 Jul 2021
- Last updated
- 8 Apr 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Data sharing requests will be assessed by the Balanced Study Steering.Committee. Individual, deidentified participant data used in these analyses will be shared 2 years after publication by request from any qualified investigator after approval of a protocol, statistical analysis plan, and receipt of a signed data access agreement via the Research Office of Auckland District Health Board, New Zealand; and after obtaining the approval of the New Zealand Health and Disability Ethics Committees for the project and data release
Study at a glance
From the registry record, last updated by the sponsor on 8 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Depth of Anaesthesia and Long-term Survival in Elderly Surgical Patients: The Balanced Anaesthesia Study Long-term Follow-up Study
- ClinicalTrials.gov ID
- NCT04965324
- Acronym / sponsor ID
- BALANCEDLT / A+9283
- Conditions
- Post-Operative Confusion, Long Term Adverse Effects, Surgery--Complications, Cognitive Dysfunction, Postoperative
- Keywords
- Anesthesia, Delirium, Incidence, Long Term Survival
- Study type
- Observational
- Recruitment status
- Active, not recruiting
- Enrolment
- 6,644 participants (actual)
- Lead sponsor
- Auckland City HospitalOther government
- Collaborators
- Health Research Council, New Zealand, Australian and New Zealand College of Anaesthetists
- Study start
- 19 Dec 2012 (actual)
- Primary completion
- 30 Jun 2026 (estimated)
- Study completion
- 31 Aug 2026 (estimated)
- First posted
- 16 Jul 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Anaesthetic depth and complications after major surgery: an international, randomised controlled trial - The BALANCED trial.
In this large, international, randomised controlled trial that enrolled patients aged 60 years and over with significant comorbidity and at increased risk of complications after major surgery, we found no evidence that light general anaesthesia (bispectral index 50) was superior to deep general anaesthesia (bispectral index 35) in reducing 1-year mortality. The BALANCED long term follow up study will look at whether depth of anesthesia affects long term (beyond 1 year) survival.
The primary hypothesis is that targetting BIS 50 will result in superior long term survival compared to targetting BIS 35.
The two secondary hypotheses are that BIS titration to BIS 50 will
- reduce local cancer recurrence or metastatic spread and consequently improve long-term survival
- reduce postoperative delirium and associated cognitive impairment and consequently improve long-term survival
Both these mechanisms would be expected to take longer to manifest as reduced survival than 1-year all-cause mortality primary outcome in the Balanced trial. Trials of cancer outcomes often use 5-year survival or similar timeframes to determine evidence of clinical benefit. A steeper cognitive trajectory due to intermediate outcomes such as delirium and cognitive impairment may take longer than 1 year to produce a clinically important difference in survival 30. The 10.6% relative risk reduction seen in the Balanced trial could translate to a statistically and clinically meaningful survival difference in this high-risk population. This population may have 5-year survival of ~80% translating to an absolute survival difference of ~2% potentially (if the ~10% RRR is maintained beyond 1 year). The alternative is that there is no long-term mortality difference which would provide continuing clinical guidance of the safety of current practice in patients who are not at high risk of delirium. This study could provide a rationale for trials in larger populations (such as the total Balanced trial population) or targeted subgroups such as cancer and delirium to provide further mechanistic insights.
Long-term survival is an important patient-centred outcome. The mechanisms described above may manifest in longer-term outcomes providing a clear rationale for the current trial.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Anaesthesia Depth BIS 35 | – | Other: Anaesthesia DepthBIS 35 |
| Anaesthesia Depth BIS 50 | – | Other: Anaesthesia DepthBIS 50 |
Who may qualify
- Ages
- 60 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- All participants who were recruited to the BALANCED Trial and who met the inclusion and no exclusion criteria for analysis of the long term outcome.
Key inclusion criteria (6 listed)
- Age over 60 years and over
- ASA physical status 3 or 4
- Surgery expected to last over 2 hours
- Hospital length of stay expected to be 2 nights or more
- General anaesthesia with or without major regional block
Key exclusion criteria (8 listed)
- Unable to monitor BIS
- Unable to consent
- Surgery with 'wake up' test
- Propofol infusion for part or all of maintenance of anaesthesia
- Previous enrolment in Balanced study
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Anaesthesia Depth | Other | Anaesthesia Depth BIS 35, Anaesthesia Depth BIS 50 |
Primary outcome
Survival
Time frame: Between one year and eight years after randomization to the BALANCED Trial
Survival
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Apr 2026.
- Individual participant dataSharing planned: Yes. Data sharing requests will be assessed by the Balanced Study Steering.Committee. Individual, deidentified participant data used in these analyses will be shared 2 years after publication by request from any qualified investigator after approval of a protocol, statistical analysis plan, and receipt of a signed data access agreement via the Research Office of Auckland District Health Board, New Zealand; and after obtaining the approval of the New Zealand Health and Disability Ethics Committees for the project and data release
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Timothy Dr Short principal investigator
Auckland City Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Post-Operative Confusion and Long Term Adverse Effects, run by Auckland City Hospital at 1 site in New Zealand.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 8 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in New Zealand. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Survival (time frame: Between one year and eight years after randomization to the BALANCED Trial). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Apr 2026; AzTrials last refreshed its copy on 26 Oct 2026.