Table 2.
Characteristics of included studies
| First author (year) | Country | Study type | Sample size (EEG/Control) | Mean age (years) | Sex (M/F) | Surgery type | Anesthesia type | EEG modality | POCD (EEG/Control) | POCD assessment tool | Postop assessment timepoints |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ballard et al. (2012) | UK | RCT | 34/39 | 75.69 ± 7.40/75.16 ± 6.51 | 28%/72% (EEG); 32%/68% (Control) | Orthopedic and abdominal surgery | General anesthesia (propofol induction, isoflurane maintenance) | BIS (Bispectral Index) and cerebral oxygen saturation (rSO2) monitoring | 1 week: Mild 57.9%/89.3%, Moderate 26.3%/57.1%; 12 weeks: Mild 54.2%/81.8%; 52 weeks: Mild 55.6%/84.4%, Moderate 11.1%/37.5% | MMSE, Cognitive Drug Research (CDR) system (reaction time, vigilance), Trail Making Test | 1 week, 12 weeks, 52 weeks |
| Besch et al. (2018) | France | RCT | 136/68 | - | - | Non-cardiac surgery | Target-controlled infusion of propofol and remifentanil (general anesthesia) | BIS (Bispectral Index) | - | MMSE, Mattis Dementia Rating Scale, Trail Making Test (TMT-A, TMT-B), Stroop tests, Isaacs Set Test (IST), Memory Impairment Screen (MIS) test, crossing-off test | Within 72 h after surgery |
| Chan et al. (2013) | China | RCT |
BIS group: 450 Control group: 452 |
BIS group: 68.1 ± 8.2 Control group: 67.6 ± 8.3 |
Male: 62.2% (BIS); 60.4% (Control) | Major non-cardiac surgery | General anesthesia (propofol, volatile anesthetics) | BIS (Bispectral Index) |
1 week: 21.7% (BIS) vs. 23.1% (Control) (P = 0.06) 3 months: 10.2% (BIS) vs. 14.7% (Control) (P = 0.02) |
Cognitive Failure Questionnaire (CFQ), Verbal Fluency Test, Chinese Auditory Verbal Learning Test, Color Trial Making Test | 1 week, 3 months |
| Evered et al. (2021) | USA, China, Australia, New Zealand | Multicenter RCT | 515 patients (BIS group: 253; Control group: 262) | BIS group: 70.8; Control group: 71.1 | Male: 64% (BIS group); 65% (Control group) | Major surgery (intra-abdominal, spinal, thoracic, vascular, etc.) | Volatile anesthetic-based general anesthesia | BIS (Bispectral Index) | BIS group: 19%; Control group: 28% (OR 0.58, P = 0.010) | 3D-CAM, CAM-ICU, MMSE, Abbreviated Mental Test Score (AMTS) | 5 days postoperatively, discharge, 30 days, 1 year |
| Fritz et al. (2020) | USA | RCT | 1113 patients (EEG-guided: 555; usual care: 558) | - | - | Elective major surgery under general anesthesia | Volatile anesthetic-based general anesthesia | BIS (Bispectral Index) | EEG-guided: 208; usual care: 222 | Confusion Assessment Method (CAM), Chart Abstraction for Delirium (CHART-DEL) | Postoperative days 1–5 |
| Kunst et al. (2020) | UK | RCT | 82 (Intervention: 42; Control: 40) | 71.6 (5.0)/72.0 (4.3) | Male: 79%/85% | Coronary artery bypass graft (CABG) | General anesthesia (isoflurane) | BIS (Bispectral Index) and regional cerebral oxygen saturation (rScO₂) | 6 weeks: MMSE 27 vs. 29 (P = 0.12); Delirium: 2.4% vs. 20% (P = 0.01) | Mini-Mental State Examination (MMSE), Confusion Assessment Method (CAM) | 3–5 days, 6 weeks, 1 year |
| Liu et al. (2023) | China | RCT | 26 (BS)/27 (NBS) | 74 ± 5 (BS)/73 ± 6 (NBS) | 12/14 (BS)/12/15 (NBS) | Elective general anesthesia surgery | Etomidate target-controlled infusion combined with sevoflurane and remifentanil | BIS (Bispectral Index) monitoring for burst suppression | MMSE scores: 1 st and 3rd days postop lower in BS group vs. NBS group (P < 0.05) | Mini-Mental State Examination (MMSE) | 1 day, 3 days, 7 days |
| Radtke et al. (2013) | Germany | RCT | 1155 (575 BIS-guided/580 blinded) | 69.7 ± 6.3 (BIS-guided)/70.1 ± 6.5 (blinded) | 257/318 (BIS-guided)/276/304 (blinded) | General, orthopedic, urologic, etc. | Total intravenous or volatile anesthesia | BIS (Bispectral Index) | Delirium: 16.7% (BIS-guided) vs. 21.4% (blinded) (P = 0.036); POCD: 7th day P = 0.062, 90th day P = 0.372 | CANTAB cognitive tests, DSM-IV criteria for delirium | 1 week, 3 months |
| Tang et al. (2020) | USA | RCT | 204 patients (102 intervention/102 standard care) | 72 ± 5 | - | Elective non-cardiac surgery | Propofol-based general anesthesia | SEDline Brain Function Monitor (Patient State Index, PSI) | Delirium: 17% (intervention) vs. 20% (standard care) | Confusion Assessment Method (CAM) | Postoperative days 1–3 |
| Xue et al. (2025) | China | RCT | 98 patients (SGB group [n = 51], Control group [n = 47]) | - | - | Laparoscopic gastrointestinal surgery | General anesthesia with/without ultrasound-guided stellate ganglion block (SGB) | - | POCD incidence: SGB group lower at day 1 (p < 0.05) | Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) | Postoperative days 1, 3 |
EEG modality: Types of electroencephalography monitoring used, including BIS (Bispectral Index), Entropy, PSI (Patient State Index), etc
Surgery type: Categories of surgery, including non-cardiac, orthopedic, and general surgery
Assessment tools: Cognitive assessment tools, such as MMSE (Mini-Mental State Examination), MoCA (Montreal Cognitive Assessment), TICS (Telephone Interview for Cognitive Status), etc
Postop assessment timepoints: Timepoints for postoperative cognitive function assessment, represented by POD (Postoperative Day)
Abbreviations: RCT Randomized Controlled Trial, EEG Electroencephalography, BIS Bispectral Index, rSO2rScO2 Regional Cerebral Oxygen Saturation, MMSE Mini-Mental State Examination, CDR Cognitive Drug Research, TMT-A/TMT-B Trail Making Test Part A/Part B, IST Isaacs Set Test, MIS Memory Impairment Screen, CFQ Cognitive Failure Questionnaire, 3D-CAM 3D Cognitive Assessment Model (specific interpretation may depend on the study context), CAM-ICU Confusion Assessment Method for the Intensive Care Unit, AMTS Abbreviated Mental Test Score, CHART-DEL Chart Abstraction for Delirium, PSI Patient State Index, CANTAB Cambridge Neuropsychological Test Automated Battery, DSM-IV Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, MoCA Montreal Cognitive Assessment, SGB Stellate Ganglion Block, POD Postoperative Day