The goal of this clinical trial (Balanced-2 study) is to compare light to deep general anesthesia using widely available brain monitors, to see if 'light' anesthesia could reduce rates of delirium, cognitive decline, and disability in older adults undergoing major surgery.
Delirium is the most common serious surgical complication, occurring in an estimated one in four older adults undergoing major surgery. Delirium causes significant distress to patients and family, and is associated with prolonged hospital stay, physical disability, progression to dementia-like illnesses, and discharge to long-term care. Between 10 - 30% of adults aged 70 years and above have surgery every year, and preserving brain health and wellbeing is an important priority during this time.
Older adults (aged ≥65 years, or Indigenous, Pacific patients aged ≥55 years) undergoing major surgery with general anesthesia (excluding heart and brain surgery) and able to provide consent will be able to participate. Participants will be randomized to two groups - a lighter general anesthesia group and a deeper general anesthesia group using processed electroencephalography (a brain monitor that provides information on depth of anesthesia using brain waves). The anesthesiologist will titrate anesthetic drugs according to the brain monitor. Participants will be followed up to determine if they experience delirium after surgery, and longer term impact of delirium such as cognitive and physical decline will also be measured.
If found to be effect, this simple, cheap, and widely available treatment could reduce disability, preserve brain health and wellbeing of many older adults undergoing surgery worldwide, and save millions in healthcare dollars.
Patients aged ≥ 65 years, and Māori, Pacific or Indigenous participants aged ≥ 55 years who are undergoing major elective or non-elective surgery with expected surgical duration ≥ 2 hours and postoperative hospital stay ≥ 2 nights.
Having general anesthesia using total intravenous anesthesia (TIVA) with pEEG monitoring
Able to provide informed consent (including patients with mild preoperative neurocognitive disorders)
Intracranial or cardiac surgery
Undergoing surgery with 'wake up' test
Previous enrollment in Balanced-2 study
Terminal illness with expected survival <3 months
Parallel
Depth of anesthesia titration using pEEG
BehavioralTitration of maintenance anesthetic agent (propofol infusion)
Incidence of postoperative delirium (POD)
Assessed using the Three-minute Diagnostic Interview for the Confusion Assessment Method (3D-CAM) or if patients are in the intensive care unit (ICU), the Confusion Assessment Method for the ICU (CAM-ICU). Delirium testing will occur between 0600 and 1000 and 1800 to 2200 daily including weekends. Delirium is present if both features (1) altered mental status/fluctuating course and (2) inattention are present, and features (3) altered level of consciousness, OR (4) disorganized thinking are present.
Incidence of severe delirium
Assessed using Confusion Assessment Method - Severity Short Form (CAM-S) The CAM-S uses the 4 features of delirium and rates them as absent, mild or marked. Possible scores are o to 7, with higher scores indicating more severe delirium.
Incidence of new mild and major postoperative neurocognitive disorders
Diagnosis of new postoperative neurocognitive disorder requires 1) subjective complaint using standardized questionnaire, 2) objective testing using Mini-Addenbrooke's Cognitive Examination (ACE), and for a diagnosis of major postoperative neurocognitive disorder, 3) evidence of functional decline using Lawton-Brody's instrumental activities of daily living (ADL) scale. The Mini-ACE questionnaire is scored out of 30, with lower scores indicating more severe cognitive impairment. The Lawton-Brody's instrumental ADL scale is scored out of 8 for women, and 5 for men, with higher scores indicating more independence.
Postoperative cognitive decline
Defined by a 2 or more-point drop in Mini-Addenbrooke's Cognitive Examination scores. The Mini-ACE questionnaire is scored out of 30, with lower scores indicating more severe cognitive impairment.
Functional decline
As measured by the change in Lawton-Brody's instrumental ADL scores The Lawton-Brody's instrumental ADL scale is scored out of 8 for women, and 5 for men, with higher scores indicating more independence.
Incidence of awareness
Assessed using Brice questionnaire. The Brice questionnaire uses 6 questions to determine if there was risk of awareness under general anesthesia.
Adverse and serious adverse events
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