Table 1. Characteristics of included studies.
BIS: bispectral index; POCD: postoperative cognitive dysfunction; MMSE: Mini-Mental State Exam; SA: spinal anaesthesia; GA: general anesthesia; POD: postoperative delirium; LOS: length of hospital stay; NTI: Narcotrend Index; MAC: minimum alveolar concentration; rScO2: regional cerebral tissue oxygenation; OAA/S: modified observer’s assessment of sedation score; ETAC: End-tidal anesthetic concentration.
| Study | Type of surgery | Age (years) | Sample Size | Treatment arms | Outcome |
| Ballard et al. (2012) [20] | Elective orthopaedic and abdominal surgery | >=60 | 72 | Combined BIS and cerebral oxygenation monitoring vs control | POCD and MMSE at one week, three months and one year |
| Brown et al. (2021) [21] | Elective spinal surgery | >= 65 | 217 | SA with sedation (targeted BIS) vs GA (masked BIS) | POD, mortality, LOS |
| Chan et al. (2013) [22] | Elective major surgery | >=60 | 921 | BIS-guided (n=462) vs no BIS-guided (n=459) | POD, POCD at day 7 and three months, mortality, LOS |
| Chen et al. (2021) [23] | VATS lobectomy | >= 65 | 73 | NTI 50-59 vs NTI 30-39 | POD, MMSE |
| Evered et al. (2021) [13] | Major surgery | >=60 | 515 | High BIS 50 (n=253) vs Low BIS 35 (n=262) | POD, MMSE |
| Hou et al. (2018) [24] | Elective total knee replacement | >=60 | 60 | High BIS 55-65 (n=30) vs Low BIS 40-50 (n=30) | POCD at day 7 and three months |
| Kunst et al. (2019) [9] | Elective coronary artery bypass graft surgery on cardiopulmonary bypass | >=65 | 82 | BIS and rScO2-guided (n=42) vs BIS and rScO2-blinded (n=40) | POD, MMSE, LOS |
| Quan et al. (2019) [10] | Abdominal surgery | >=65 | 120 | Low BIS 30-45 (n=60) vs High BIS 45-60 (n=60) | POCD at day 7 and three months, mortality, LOS |
| Radtke et al. (2013) [25] | Abdominal, thoracic, vascular, orthopaedic, otorhinolaryngological, oral and maxillofacial, gynaecological, and urologic surgery | >=60 | 1155 | BIS-guided (n=575) vs BIS-blinded (n=580) | POD, POCD at day 7 and three months, morality, LOS |
| Sadek et al. (2010) [26] | Elective spine surgery | >=60 | 40 | BIS-targeted (50-55) (n=20) and MAC-targeted (n=20) | MMSE |
| Sieber et al. (2010) [27] | Hip fracture repair | >=65 | 114 | BIS 50 (n=57) vs BIS>=80 (n=57) | POD, MMSE, mortality, LOS |
| Sieber et al. (2018) [28] | Non-elective hip fracture repair | >=65 | 200 | OAA/S Heavier (modified observer’s assessment of sedation score of 0-2) (n=100) or lighter (observer’s assessment of sedation score of 3-5) (n=100) | POD, MMSE, LOS |
| Valentin et al. (2016) [19] | Elective non-cardiac and non-neurologic surgery | >=60 | 140 | control + low BIS 35-45 (n=40) vs control + high BIS 46-55 (n=32) vs dexamethasone + low BIS (n=36) vs dexamethasone + high BIS (n=32) | POCD at day 7 and three months |
| Whitlock et al. (2014) [29] | Cardiothoracic patients | >60 | 310 | BIS vs ETAC | POD |
| Wildes et al. (2019) [11] | Major surgeries (e.g., cardiac, gastrointestinal, thoracic, gynecologic, hepatobiliary-pancreatic, urologic, vascular) | >=60 | 1232 | BIS-guided (n=614) vs usual care (n=618) | POD, mortality, LOS |
| Wong et al. (2002) [30] | Elective knee or hip replacement surgery | >=60 | 60 | BIS group (n=29) vs standard practice group (n=31) | MMSE |
| Zhou et al. (2018) [31] | Resection of colon carcinoma | 65-75 | 81 | BIS group (n=41) vs non-BIS group (n=40) | POD |