Chan 2013.
| Methods | Design: Prospective randomised double‐blinded parallel group study assessing BIS‐guided anaesthesia in elective surgical patients Date of study: January 2007‐December 2009 Power calculation: Not for delirium as delirium was a secondary outcome. Study underpowered given delirium rate of 20% Frequency of outcomes assessment: mornings after surgery, 1 week, 3 months Inclusion criteria: > 60yrs old; scheduled for elective major surgery anticipated to last > 2 hours or longer which has an anticipated hospital stay of at least 4 days Exclusion criteria: unavailable/unable to co‐operate with interviews; illiteracy; hearing/visual impairment; major psychosis; CNS diseases; suspected dementia/MMSE 23 or less |
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| Participants | Number in study: 921 Country: Hong‐Kong Setting: General hospital Age: Mean age of 68.1 (SD 8.2) in intervention group 67.6 (SD 8.3) in control group Sex: 62.2% of intervention group and 60.4% of control group were male Co‐morbidity: no significant differences in pre‐existing medical conditions (cardiovascular, respiratory, endocrine or other) between intervention and control groups Dementia: Excluded is MMSE 23 or less |
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| Interventions | Intervention: BIS‐guided anaesthesia ‐ anaesthetic dosage adjusted to maintain BIS value between 40‐60 from commencement of anaesthesia to the end of surgery; alarm sounded when out of range Control: Routine care, anaesthetic drug administration was titrated according to clinical judgment. BIS monitoring was continued in this group, but the BIS number, its trend, and the EEG waveform were omitted from the display, specifically designed for this trial |
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| Outcomes | 1. Incident delirium, measured using CAM 2. Length of admission 3. Cognitive status (postoperative cognitive dysfunction) at 1 week and 3 months 4. Mortality at 1 week and 3 months 5. Postoperative complications 6. Psychological morbidity, measured using Short‐Form‐36 Mental Score |
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| Notes | Funding source: Research Grants Council of Hong Kong and Health and Health Services Research Fund Declarations of interest: "The authors have no conflicts of interest to disclose" Delirium not excluded at enrolment |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Allocation concealment (selection bias) | Low risk | No evidence that allocations know |
| Random sequence generation (selection bias) | Low risk | Computer‐generated random assignment accessed via intranet |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Patients, surgeons and all research staff were blinded but, concern re: anaesthetists and theatre team in view of alarm system for intervention group only |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Outcome assessors blinded |
| Incomplete outcome data (attrition bias) All outcomes | High risk | Outcome data available for n = 783 at one week and n = 835 at 3 months but n = 921 were randomised. Reasons for exclusion reported: n = 80 were excluded in the intervention group and n = 58 in the control group at one week; n = 32 were excluded in the intervention group and n = 25 in the control group at three months. In n = 97 cases participants were not assessed at one week due to being 'unfit for testing', compared with n = 5 at three months |
| Selective reporting (reporting bias) | Unclear risk | Limited protocol available on Centre for Clinical Trials online registry |
| Other bias | Low risk | No evidence of other bias |